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Diffstat (limited to 'Documentation/driver-api')
| -rw-r--r-- | Documentation/driver-api/acpi/index.rst | 9 | ||||
| -rw-r--r-- | Documentation/driver-api/acpi/linuxized-acpica.rst | 279 | ||||
| -rw-r--r-- | Documentation/driver-api/acpi/scan_handlers.rst | 83 | ||||
| -rw-r--r-- | Documentation/driver-api/component.rst | 2 | ||||
| -rw-r--r-- | Documentation/driver-api/device-io.rst | 45 | ||||
| -rw-r--r-- | Documentation/driver-api/generic-counter.rst | 342 | ||||
| -rw-r--r-- | Documentation/driver-api/gpio/driver.rst | 361 | ||||
| -rw-r--r-- | Documentation/driver-api/index.rst | 2 | ||||
| -rw-r--r-- | Documentation/driver-api/pci/p2pdma.rst | 4 | ||||
| -rw-r--r-- | Documentation/driver-api/pm/cpuidle.rst | 7 | ||||
| -rw-r--r-- | Documentation/driver-api/pm/devices.rst | 12 | ||||
| -rw-r--r-- | Documentation/driver-api/pm/index.rst | 2 | ||||
| -rw-r--r-- | Documentation/driver-api/pm/notifiers.rst | 8 | ||||
| -rw-r--r-- | Documentation/driver-api/pm/types.rst | 2 | ||||
| -rw-r--r-- | Documentation/driver-api/soundwire/stream.rst | 16 | ||||
| -rw-r--r-- | Documentation/driver-api/uio-howto.rst | 4 |
16 files changed, 979 insertions, 199 deletions
diff --git a/Documentation/driver-api/acpi/index.rst b/Documentation/driver-api/acpi/index.rst new file mode 100644 index 000000000000..ace0008e54c2 --- /dev/null +++ b/Documentation/driver-api/acpi/index.rst @@ -0,0 +1,9 @@ +============ +ACPI Support +============ + +.. toctree:: + :maxdepth: 2 + + linuxized-acpica + scan_handlers diff --git a/Documentation/driver-api/acpi/linuxized-acpica.rst b/Documentation/driver-api/acpi/linuxized-acpica.rst new file mode 100644 index 000000000000..0ca8f1538519 --- /dev/null +++ b/Documentation/driver-api/acpi/linuxized-acpica.rst @@ -0,0 +1,279 @@ +.. SPDX-License-Identifier: GPL-2.0 +.. include:: <isonum.txt> + +============================================================ +Linuxized ACPICA - Introduction to ACPICA Release Automation +============================================================ + +:Copyright: |copy| 2013-2016, Intel Corporation + +:Author: Lv Zheng <lv.zheng@intel.com> + + +Abstract +======== +This document describes the ACPICA project and the relationship between +ACPICA and Linux. It also describes how ACPICA code in drivers/acpi/acpica, +include/acpi and tools/power/acpi is automatically updated to follow the +upstream. + +ACPICA Project +============== + +The ACPI Component Architecture (ACPICA) project provides an operating +system (OS)-independent reference implementation of the Advanced +Configuration and Power Interface Specification (ACPI). It has been +adapted by various host OSes. By directly integrating ACPICA, Linux can +also benefit from the application experiences of ACPICA from other host +OSes. + +The homepage of ACPICA project is: www.acpica.org, it is maintained and +supported by Intel Corporation. + +The following figure depicts the Linux ACPI subsystem where the ACPICA +adaptation is included:: + + +---------------------------------------------------------+ + | | + | +---------------------------------------------------+ | + | | +------------------+ | | + | | | Table Management | | | + | | +------------------+ | | + | | +----------------------+ | | + | | | Namespace Management | | | + | | +----------------------+ | | + | | +------------------+ ACPICA Components | | + | | | Event Management | | | + | | +------------------+ | | + | | +---------------------+ | | + | | | Resource Management | | | + | | +---------------------+ | | + | | +---------------------+ | | + | | | Hardware Management | | | + | | +---------------------+ | | + | +---------------------------------------------------+ | | + | | | +------------------+ | | | + | | | | OS Service Layer | | | | + | | | +------------------+ | | | + | | +-------------------------------------------------|-+ | + | | +--------------------+ | | + | | | Device Enumeration | | | + | | +--------------------+ | | + | | +------------------+ | | + | | | Power Management | | | + | | +------------------+ Linux/ACPI Components | | + | | +--------------------+ | | + | | | Thermal Management | | | + | | +--------------------+ | | + | | +--------------------------+ | | + | | | Drivers for ACPI Devices | | | + | | +--------------------------+ | | + | | +--------+ | | + | | | ...... | | | + | | +--------+ | | + | +---------------------------------------------------+ | + | | + +---------------------------------------------------------+ + + Figure 1. Linux ACPI Software Components + +.. note:: + A. OS Service Layer - Provided by Linux to offer OS dependent + implementation of the predefined ACPICA interfaces (acpi_os_*). + :: + + include/acpi/acpiosxf.h + drivers/acpi/osl.c + include/acpi/platform + include/asm/acenv.h + B. ACPICA Functionality - Released from ACPICA code base to offer + OS independent implementation of the ACPICA interfaces (acpi_*). + :: + + drivers/acpi/acpica + include/acpi/ac*.h + tools/power/acpi + C. Linux/ACPI Functionality - Providing Linux specific ACPI + functionality to the other Linux kernel subsystems and user space + programs. + :: + + drivers/acpi + include/linux/acpi.h + include/linux/acpi*.h + include/acpi + tools/power/acpi + D. Architecture Specific ACPICA/ACPI Functionalities - Provided by the + ACPI subsystem to offer architecture specific implementation of the + ACPI interfaces. They are Linux specific components and are out of + the scope of this document. + :: + + include/asm/acpi.h + include/asm/acpi*.h + arch/*/acpi + +ACPICA Release +============== + +The ACPICA project maintains its code base at the following repository URL: +https://github.com/acpica/acpica.git. As a rule, a release is made every +month. + +As the coding style adopted by the ACPICA project is not acceptable by +Linux, there is a release process to convert the ACPICA git commits into +Linux patches. The patches generated by this process are referred to as +"linuxized ACPICA patches". The release process is carried out on a local +copy the ACPICA git repository. Each commit in the monthly release is +converted into a linuxized ACPICA patch. Together, they form the monthly +ACPICA release patchset for the Linux ACPI community. This process is +illustrated in the following figure:: + + +-----------------------------+ + | acpica / master (-) commits | + +-----------------------------+ + /|\ | + | \|/ + | /---------------------\ +----------------------+ + | < Linuxize repo Utility >-->| old linuxized acpica |--+ + | \---------------------/ +----------------------+ | + | | + /---------\ | + < git reset > \ + \---------/ \ + /|\ /+-+ + | / | + +-----------------------------+ | | + | acpica / master (+) commits | | | + +-----------------------------+ | | + | | | + \|/ | | + /-----------------------\ +----------------------+ | | + < Linuxize repo Utilities >-->| new linuxized acpica |--+ | + \-----------------------/ +----------------------+ | + \|/ + +--------------------------+ /----------------------\ + | Linuxized ACPICA Patches |<----------------< Linuxize patch Utility > + +--------------------------+ \----------------------/ + | + \|/ + /---------------------------\ + < Linux ACPI Community Review > + \---------------------------/ + | + \|/ + +-----------------------+ /------------------\ +----------------+ + | linux-pm / linux-next |-->< Linux Merge Window >-->| linux / master | + +-----------------------+ \------------------/ +----------------+ + + Figure 2. ACPICA -> Linux Upstream Process + +.. note:: + A. Linuxize Utilities - Provided by the ACPICA repository, including a + utility located in source/tools/acpisrc folder and a number of + scripts located in generate/linux folder. + B. acpica / master - "master" branch of the git repository at + <https://github.com/acpica/acpica.git>. + C. linux-pm / linux-next - "linux-next" branch of the git repository at + <http://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm.git>. + D. linux / master - "master" branch of the git repository at + <http://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git>. + + Before the linuxized ACPICA patches are sent to the Linux ACPI community + for review, there is a quality assurance build test process to reduce + porting issues. Currently this build process only takes care of the + following kernel configuration options: + CONFIG_ACPI/CONFIG_ACPI_DEBUG/CONFIG_ACPI_DEBUGGER + +ACPICA Divergences +================== + +Ideally, all of the ACPICA commits should be converted into Linux patches +automatically without manual modifications, the "linux / master" tree should +contain the ACPICA code that exactly corresponds to the ACPICA code +contained in "new linuxized acpica" tree and it should be possible to run +the release process fully automatically. + +As a matter of fact, however, there are source code differences between +the ACPICA code in Linux and the upstream ACPICA code, referred to as +"ACPICA Divergences". + +The various sources of ACPICA divergences include: + 1. Legacy divergences - Before the current ACPICA release process was + established, there already had been divergences between Linux and + ACPICA. Over the past several years those divergences have been greatly + reduced, but there still are several ones and it takes time to figure + out the underlying reasons for their existence. + 2. Manual modifications - Any manual modification (eg. coding style fixes) + made directly in the Linux sources obviously hurts the ACPICA release + automation. Thus it is recommended to fix such issues in the ACPICA + upstream source code and generate the linuxized fix using the ACPICA + release utilities (please refer to Section 4 below for the details). + 3. Linux specific features - Sometimes it's impossible to use the + current ACPICA APIs to implement features required by the Linux kernel, + so Linux developers occasionally have to change ACPICA code directly. + Those changes may not be acceptable by ACPICA upstream and in such cases + they are left as committed ACPICA divergences unless the ACPICA side can + implement new mechanisms as replacements for them. + 4. ACPICA release fixups - ACPICA only tests commits using a set of the + user space simulation utilities, thus the linuxized ACPICA patches may + break the Linux kernel, leaving us build/boot failures. In order to + avoid breaking Linux bisection, fixes are applied directly to the + linuxized ACPICA patches during the release process. When the release + fixups are backported to the upstream ACPICA sources, they must follow + the upstream ACPICA rules and so further modifications may appear. + That may result in the appearance of new divergences. + 5. Fast tracking of ACPICA commits - Some ACPICA commits are regression + fixes or stable-candidate material, so they are applied in advance with + respect to the ACPICA release process. If such commits are reverted or + rebased on the ACPICA side in order to offer better solutions, new ACPICA + divergences are generated. + +ACPICA Development +================== + +This paragraph guides Linux developers to use the ACPICA upstream release +utilities to obtain Linux patches corresponding to upstream ACPICA commits +before they become available from the ACPICA release process. + + 1. Cherry-pick an ACPICA commit + + First you need to git clone the ACPICA repository and the ACPICA change + you want to cherry pick must be committed into the local repository. + + Then the gen-patch.sh command can help to cherry-pick an ACPICA commit + from the ACPICA local repository:: + + $ git clone https://github.com/acpica/acpica + $ cd acpica + $ generate/linux/gen-patch.sh -u [commit ID] + + Here the commit ID is the ACPICA local repository commit ID you want to + cherry pick. It can be omitted if the commit is "HEAD". + + 2. Cherry-pick recent ACPICA commits + + Sometimes you need to rebase your code on top of the most recent ACPICA + changes that haven't been applied to Linux yet. + + You can generate the ACPICA release series yourself and rebase your code on + top of the generated ACPICA release patches:: + + $ git clone https://github.com/acpica/acpica + $ cd acpica + $ generate/linux/make-patches.sh -u [commit ID] + + The commit ID should be the last ACPICA commit accepted by Linux. Usually, + it is the commit modifying ACPI_CA_VERSION. It can be found by executing + "git blame source/include/acpixf.h" and referencing the line that contains + "ACPI_CA_VERSION". + + 3. Inspect the current divergences + + If you have local copies of both Linux and upstream ACPICA, you can generate + a diff file indicating the state of the current divergences:: + + # git clone https://github.com/acpica/acpica + # git clone http://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git + # cd acpica + # generate/linux/divergences.sh -s ../linux diff --git a/Documentation/driver-api/acpi/scan_handlers.rst b/Documentation/driver-api/acpi/scan_handlers.rst new file mode 100644 index 000000000000..7a197b3a33fc --- /dev/null +++ b/Documentation/driver-api/acpi/scan_handlers.rst @@ -0,0 +1,83 @@ +.. SPDX-License-Identifier: GPL-2.0 +.. include:: <isonum.txt> + +================== +ACPI Scan Handlers +================== + +:Copyright: |copy| 2012, Intel Corporation + +:Author: Rafael J. Wysocki <rafael.j.wysocki@intel.com> + +During system initialization and ACPI-based device hot-add, the ACPI namespace +is scanned in search of device objects that generally represent various pieces +of hardware. This causes a struct acpi_device object to be created and +registered with the driver core for every device object in the ACPI namespace +and the hierarchy of those struct acpi_device objects reflects the namespace +layout (i.e. parent device objects in the namespace are represented by parent +struct acpi_device objects and analogously for their children). Those struct +acpi_device objects are referred to as "device nodes" in what follows, but they +should not be confused with struct device_node objects used by the Device Trees +parsing code (although their role is analogous to the role of those objects). + +During ACPI-based device hot-remove device nodes representing pieces of hardware +being removed are unregistered and deleted. + +The core ACPI namespace scanning code in drivers/acpi/scan.c carries out basic +initialization of device nodes, such as retrieving common configuration +information from the device objects represented by them and populating them with +appropriate data, but some of them require additional handling after they have +been registered. For example, if the given device node represents a PCI host +bridge, its registration should cause the PCI bus under that bridge to be +enumerated and PCI devices on that bus to be registered with the driver core. +Similarly, if the device node represents a PCI interrupt link, it is necessary +to configure that link so that the kernel can use it. + +Those additional configuration tasks usually depend on the type of the hardware +component represented by the given device node which can be determined on the +basis of the device node's hardware ID (HID). They are performed by objects +called ACPI scan handlers represented by the following structure:: + + struct acpi_scan_handler { + const struct acpi_device_id *ids; + struct list_head list_node; + int (*attach)(struct acpi_device *dev, const struct acpi_device_id *id); + void (*detach)(struct acpi_device *dev); + }; + +where ids is the list of IDs of device nodes the given handler is supposed to +take care of, list_node is the hook to the global list of ACPI scan handlers +maintained by the ACPI core and the .attach() and .detach() callbacks are +executed, respectively, after registration of new device nodes and before +unregistration of device nodes the handler attached to previously. + +The namespace scanning function, acpi_bus_scan(), first registers all of the +device nodes in the given namespace scope with the driver core. Then, it tries +to match a scan handler against each of them using the ids arrays of the +available scan handlers. If a matching scan handler is found, its .attach() +callback is executed for the given device node. If that callback returns 1, +that means that the handler has claimed the device node and is now responsible +for carrying out any additional configuration tasks related to it. It also will +be responsible for preparing the device node for unregistration in that case. +The device node's handler field is then populated with the address of the scan +handler that has claimed it. + +If the .attach() callback returns 0, it means that the device node is not +interesting to the given scan handler and may be matched against the next scan +handler in the list. If it returns a (negative) error code, that means that +the namespace scan should be terminated due to a serious error. The error code +returned should then reflect the type of the error. + +The namespace trimming function, acpi_bus_trim(), first executes .detach() +callbacks from the scan handlers of all device nodes in the given namespace +scope (if they have scan handlers). Next, it unregisters all of the device +nodes in that scope. + +ACPI scan handlers can be added to the list maintained by the ACPI core with the +help of the acpi_scan_add_handler() function taking a pointer to the new scan +handler as an argument. The order in which scan handlers are added to the list +is the order in which they are matched against device nodes during namespace +scans. + +All scan handles must be added to the list before acpi_bus_scan() is run for the +first time and they cannot be removed from it. diff --git a/Documentation/driver-api/component.rst b/Documentation/driver-api/component.rst index 2da4a8f20607..57e37590733f 100644 --- a/Documentation/driver-api/component.rst +++ b/Documentation/driver-api/component.rst @@ -1,3 +1,5 @@ +.. _component: + ====================================== Component Helper for Aggregate Drivers ====================================== diff --git a/Documentation/driver-api/device-io.rst b/Documentation/driver-api/device-io.rst index b00b23903078..0e389378f71d 100644 --- a/Documentation/driver-api/device-io.rst +++ b/Documentation/driver-api/device-io.rst @@ -103,51 +103,6 @@ continuing execution:: ha->flags.ints_enabled = 0; } -In addition to write posting, on some large multiprocessing systems -(e.g. SGI Challenge, Origin and Altix machines) posted writes won't be -strongly ordered coming from different CPUs. Thus it's important to -properly protect parts of your driver that do memory-mapped writes with -locks and use the :c:func:`mmiowb()` to make sure they arrive in the -order intended. Issuing a regular readX() will also ensure write ordering, -but should only be used when the -driver has to be sure that the write has actually arrived at the device -(not that it's simply ordered with respect to other writes), since a -full readX() is a relatively expensive operation. - -Generally, one should use :c:func:`mmiowb()` prior to releasing a spinlock -that protects regions using :c:func:`writeb()` or similar functions that -aren't surrounded by readb() calls, which will ensure ordering -and flushing. The following pseudocode illustrates what might occur if -write ordering isn't guaranteed via :c:func:`mmiowb()` or one of the -readX() functions:: - - CPU A: spin_lock_irqsave(&dev_lock, flags) - CPU A: ... - CPU A: writel(newval, ring_ptr); - CPU A: spin_unlock_irqrestore(&dev_lock, flags) - ... - CPU B: spin_lock_irqsave(&dev_lock, flags) - CPU B: writel(newval2, ring_ptr); - CPU B: ... - CPU B: spin_unlock_irqrestore(&dev_lock, flags) - -In the case above, newval2 could be written to ring_ptr before newval. -Fixing it is easy though:: - - CPU A: spin_lock_irqsave(&dev_lock, flags) - CPU A: ... - CPU A: writel(newval, ring_ptr); - CPU A: mmiowb(); /* ensure no other writes beat us to the device */ - CPU A: spin_unlock_irqrestore(&dev_lock, flags) - ... - CPU B: spin_lock_irqsave(&dev_lock, flags) - CPU B: writel(newval2, ring_ptr); - CPU B: ... - CPU B: mmiowb(); - CPU B: spin_unlock_irqrestore(&dev_lock, flags) - -See tg3.c for a real world example of how to use :c:func:`mmiowb()` - PCI ordering rules also guarantee that PIO read responses arrive after any outstanding DMA writes from that bus, since for some devices the result of a readb() call may signal to the driver that a DMA transaction is diff --git a/Documentation/driver-api/generic-counter.rst b/Documentation/driver-api/generic-counter.rst new file mode 100644 index 000000000000..0c161b1a3be6 --- /dev/null +++ b/Documentation/driver-api/generic-counter.rst @@ -0,0 +1,342 @@ +.. SPDX-License-Identifier: GPL-2.0 + +========================= +Generic Counter Interface +========================= + +Introduction +============ + +Counter devices are prevalent within a diverse spectrum of industries. +The ubiquitous presence of these devices necessitates a common interface +and standard of interaction and exposure. This driver API attempts to +resolve the issue of duplicate code found among existing counter device +drivers by introducing a generic counter interface for consumption. The +Generic Counter interface enables drivers to support and expose a common +set of components and functionality present in counter devices. + +Theory +====== + +Counter devices can vary greatly in design, but regardless of whether +some devices are quadrature encoder counters or tally counters, all +counter devices consist of a core set of components. This core set of +components, shared by all counter devices, is what forms the essence of +the Generic Counter interface. + +There are three core components to a counter: + +* Count: + Count data for a set of Signals. + +* Signal: + Input data that is evaluated by the counter to determine the count + data. + +* Synapse: + The association of a Signal with a respective Count. + +COUNT +----- +A Count represents the count data for a set of Signals. The Generic +Counter interface provides the following available count data types: + +* COUNT_POSITION: + Unsigned integer value representing position. + +A Count has a count function mode which represents the update behavior +for the count data. The Generic Counter interface provides the following +available count function modes: + +* Increase: + Accumulated count is incremented. + +* Decrease: + Accumulated count is decremented. + +* Pulse-Direction: + Rising edges on signal A updates the respective count. The input level + of signal B determines direction. + +* Quadrature: + A pair of quadrature encoding signals are evaluated to determine + position and direction. The following Quadrature modes are available: + + - x1 A: + If direction is forward, rising edges on quadrature pair signal A + updates the respective count; if the direction is backward, falling + edges on quadrature pair signal A updates the respective count. + Quadrature encoding determines the direction. + + - x1 B: + If direction is forward, rising edges on quadrature pair signal B + updates the respective count; if the direction is backward, falling + edges on quadrature pair signal B updates the respective count. + Quadrature encoding determines the direction. + + - x2 A: + Any state transition on quadrature pair signal A updates the + respective count. Quadrature encoding determines the direction. + + - x2 B: + Any state transition on quadrature pair signal B updates the + respective count. Quadrature encoding determines the direction. + + - x4: + Any state transition on either quadrature pair signals updates the + respective count. Quadrature encoding determines the direction. + +A Count has a set of one or more associated Signals. + +SIGNAL +------ +A Signal represents a counter input data; this is the input data that is +evaluated by the counter to determine the count data; e.g. a quadrature +signal output line of a rotary encoder. Not all counter devices provide +user access to the Signal data. + +The Generic Counter interface provides the following available signal +data types for when the Signal data is available for user access: + +* SIGNAL_LEVEL: + Signal line state level. The following states are possible: + + - SIGNAL_LEVEL_LOW: + Signal line is in a low state. + + - SIGNAL_LEVEL_HIGH: + Signal line is in a high state. + +A Signal may be associated with one or more Counts. + +SYNAPSE +------- +A Synapse represents the association of a Signal with a respective +Count. Signal data affects respective Count data, and the Synapse +represents this relationship. + +The Synapse action mode specifies the Signal data condition which +triggers the respective Count's count function evaluation to update the +count data. The Generic Counter interface provides the following +available action modes: + +* None: + Signal does not trigger the count function. In Pulse-Direction count + function mode, this Signal is evaluated as Direction. + +* Rising Edge: + Low state transitions to high state. + +* Falling Edge: + High state transitions to low state. + +* Both Edges: + Any state transition. + +A counter is defined as a set of input signals associated with count +data that are generated by the evaluation of the state of the associated +input signals as defined by the respective count functions. Within the +context of the Generic Counter interface, a counter consists of Counts +each associated with a set of Signals, whose respective Synapse +instances represent the count function update conditions for the +associated Counts. + +Paradigm +======== + +The most basic counter device may be expressed as a single Count +associated with a single Signal via a single Synapse. Take for example +a counter device which simply accumulates a count of rising edges on a +source input line:: + + Count Synapse Signal + ----- ------- ------ + +---------------------+ + | Data: Count | Rising Edge ________ + | Function: Increase | <------------- / Source \ + | | ____________ + +---------------------+ + +In this example, the Signal is a source input line with a pulsing +voltage, while the Count is a persistent count value which is repeatedly +incremented. The Signal is associated with the respective Count via a +Synapse. The increase function is triggered by the Signal data condition +specified by the Synapse -- in this case a rising edge condition on the +voltage input line. In summary, the counter device existence and +behavior is aptly represented by respective Count, Signal, and Synapse +components: a rising edge condition triggers an increase function on an +accumulating count datum. + +A counter device is not limited to a single Signal; in fact, in theory +many Signals may be associated with even a single Count. For example, a +quadrature encoder counter device can keep track of position based on +the states of two input lines:: + + Count Synapse Signal + ----- ------- ------ + +-------------------------+ + | Data: Position | Both Edges ___ + | Function: Quadrature x4 | <------------ / A \ + | | _______ + | | + | | Both Edges ___ + | | <------------ / B \ + | | _______ + +-------------------------+ + +In this example, two Signals (quadrature encoder lines A and B) are +associated with a single Count: a rising or falling edge on either A or +B triggers the "Quadrature x4" function which determines the direction +of movement and updates the respective position data. The "Quadrature +x4" function is likely implemented in the hardware of the quadrature +encoder counter device; the Count, Signals, and Synapses simply +represent this hardware behavior and functionality. + +Signals associated with the same Count can have differing Synapse action +mode conditions. For example, a quadrature encoder counter device +operating in a non-quadrature Pulse-Direction mode could have one input +line dedicated for movement and a second input line dedicated for +direction:: + + Count Synapse Signal + ----- ------- ------ + +---------------------------+ + | Data: Position | Rising Edge ___ + | Function: Pulse-Direction | <------------- / A \ (Movement) + | | _______ + | | + | | None ___ + | | <------------- / B \ (Direction) + | | _______ + +---------------------------+ + +Only Signal A triggers the "Pulse-Direction" update function, but the +instantaneous state of Signal B is still required in order to know the +direction so that the position data may be properly updated. Ultimately, +both Signals are associated with the same Count via two respective +Synapses, but only one Synapse has an active action mode condition which +triggers the respective count function while the other is left with a +"None" condition action mode to indicate its respective Signal's +availability for state evaluation despite its non-triggering mode. + +Keep in mind that the Signal, Synapse, and Count are abstract +representations which do not need to be closely married to their +respective physical sources. This allows the user of a counter to +divorce themselves from the nuances of physical components (such as +whether an input line is differential or single-ended) and instead focus +on the core idea of what the data and process represent (e.g. position +as interpreted from quadrature encoding data). + +Userspace Interface +=================== + +Several sysfs attributes are generated by the Generic Counter interface, +and reside under the /sys/bus/counter/devices/counterX directory, where +counterX refers to the respective counter device. Please see +Documentation/ABI/testing/sys-bus-counter-generic-sysfs for detailed +information on each Generic Counter interface sysfs attribute. + +Through these sysfs attributes, programs and scripts may interact with +the Generic Counter paradigm Counts, Signals, and Synapses of respective +counter devices. + +Driver API +========== + +Driver authors may utilize the Generic Counter interface in their code +by including the include/linux/counter.h header file. This header file +provides several core data structures, function prototypes, and macros +for defining a counter device. + +.. kernel-doc:: include/linux/counter.h + :internal: + +.. kernel-doc:: drivers/counter/counter.c + :export: + +Implementation +============== + +To support a counter device, a driver must first allocate the available +Counter Signals via counter_signal structures. These Signals should +be stored as an array and set to the signals array member of an +allocated counter_device structure before the Counter is registered to +the system. + +Counter Counts may be allocated via counter_count structures, and +respective Counter Signal associations (Synapses) made via +counter_synapse structures. Associated counter_synapse structures are +stored as an array and set to the the synapses array member of the +respective counter_count structure. These counter_count structures are +set to the counts array member of an allocated counter_device structure +before the Counter is registered to the system. + +Driver callbacks should be provided to the counter_device structure via +a constant counter_ops structure in order to communicate with the +device: to read and write various Signals and Counts, and to set and get +the "action mode" and "function mode" for various Synapses and Counts +respectively. + +A defined counter_device structure may be registered to the system by +passing it to the counter_register function, and unregistered by passing +it to the counter_unregister function. Similarly, the +devm_counter_register and devm_counter_unregister functions may be used +if device memory-managed registration is desired. + +Extension sysfs attributes can be created for auxiliary functionality +and data by passing in defined counter_device_ext, counter_count_ext, +and counter_signal_ext structures. In these cases, the +counter_device_ext structure is used for global configuration of the +respective Counter device, while the counter_count_ext and +counter_signal_ext structures allow for auxiliary exposure and +configuration of a specific Count or Signal respectively. + +Architecture +============ + +When the Generic Counter interface counter module is loaded, the +counter_init function is called which registers a bus_type named +"counter" to the system. Subsequently, when the module is unloaded, the +counter_exit function is called which unregisters the bus_type named +"counter" from the system. + +Counter devices are registered to the system via the counter_register +function, and later removed via the counter_unregister function. The +counter_register function establishes a unique ID for the Counter +device and creates a respective sysfs directory, where X is the +mentioned unique ID: + + /sys/bus/counter/devices/counterX + +Sysfs attributes are created within the counterX directory to expose +functionality, configurations, and data relating to the Counts, Signals, +and Synapses of the Counter device, as well as options and information +for the Counter device itself. + +Each Signal has a directory created to house its relevant sysfs +attributes, where Y is the unique ID of the respective Signal: + + /sys/bus/counter/devices/counterX/signalY + +Similarly, each Count has a directory created to house its relevant +sysfs attributes, where Y is the unique ID of the respective Count: + + /sys/bus/counter/devices/counterX/countY + +For a more detailed breakdown of the available Generic Counter interface +sysfs attributes, please refer to the +Documentation/ABI/testing/sys-bus-counter file. + +The Signals and Counts associated with the Counter device are registered +to the system as well by the counter_register function. The +signal_read/signal_write driver callbacks are associated with their +respective Signal attributes, while the count_read/count_write and +function_get/function_set driver callbacks are associated with their +respective Count attributes; similarly, the same is true for the +action_get/action_set driver callbacks and their respective Synapse +attributes. If a driver callback is left undefined, then the respective +read/write permission is left disabled for the relevant attributes. + +Similarly, extension sysfs attributes are created for the defined +counter_device_ext, counter_count_ext, and counter_signal_ext +structures that are passed in. diff --git a/Documentation/driver-api/gpio/driver.rst b/Documentation/driver-api/gpio/driver.rst index 3043167fc557..1ce7fcd0f989 100644 --- a/Documentation/driver-api/gpio/driver.rst +++ b/Documentation/driver-api/gpio/driver.rst @@ -1,10 +1,8 @@ -================================ -GPIO Descriptor Driver Interface -================================ +===================== +GPIO Driver Interface +===================== -This document serves as a guide for GPIO chip drivers writers. Note that it -describes the new descriptor-based interface. For a description of the -deprecated integer-based GPIO interface please refer to gpio-legacy.txt. +This document serves as a guide for writers of GPIO chip drivers. Each GPIO controller driver needs to include the following header, which defines the structures used to define a GPIO driver: @@ -15,32 +13,49 @@ the structures used to define a GPIO driver: Internal Representation of GPIOs ================================ -Inside a GPIO driver, individual GPIOs are identified by their hardware number, -which is a unique number between 0 and n, n being the number of GPIOs managed by -the chip. This number is purely internal: the hardware number of a particular -GPIO descriptor is never made visible outside of the driver. - -On top of this internal number, each GPIO also need to have a global number in -the integer GPIO namespace so that it can be used with the legacy GPIO +A GPIO chip handles one or more GPIO lines. To be considered a GPIO chip, the +lines must conform to the definition: General Purpose Input/Output. If the +line is not general purpose, it is not GPIO and should not be handled by a +GPIO chip. The use case is the indicative: certain lines in a system may be +called GPIO but serve a very particular purpose thus not meeting the criteria +of a general purpose I/O. On the other hand a LED driver line may be used as a +GPIO and should therefore still be handled by a GPIO chip driver. + +Inside a GPIO driver, individual GPIO lines are identified by their hardware +number, sometime also referred to as ``offset``, which is a unique number +between 0 and n-1, n being the number of GPIOs managed by the chip. + +The hardware GPIO number should be something intuitive to the hardware, for +example if a system uses a memory-mapped set of I/O-registers where 32 GPIO +lines are handled by one bit per line in a 32-bit register, it makes sense to +use hardware offsets 0..31 for these, corresponding to bits 0..31 in the +register. + +This number is purely internal: the hardware number of a particular GPIO +line is never made visible outside of the driver. + +On top of this internal number, each GPIO line also needs to have a global +number in the integer GPIO namespace so that it can be used with the legacy GPIO interface. Each chip must thus have a "base" number (which can be automatically -assigned), and for each GPIO the global number will be (base + hardware number). -Although the integer representation is considered deprecated, it still has many -users and thus needs to be maintained. +assigned), and for each GPIO line the global number will be (base + hardware +number). Although the integer representation is considered deprecated, it still +has many users and thus needs to be maintained. -So for example one platform could use numbers 32-159 for GPIOs, with a +So for example one platform could use global numbers 32-159 for GPIOs, with a controller defining 128 GPIOs at a "base" of 32 ; while another platform uses -numbers 0..63 with one set of GPIO controllers, 64-79 with another type of GPIO -controller, and on one particular board 80-95 with an FPGA. The numbers need not -be contiguous; either of those platforms could also use numbers 2000-2063 to -identify GPIOs in a bank of I2C GPIO expanders. +global numbers 0..63 with one set of GPIO controllers, 64-79 with another type +of GPIO controller, and on one particular board 80-95 with an FPGA. The legacy +numbers need not be contiguous; either of those platforms could also use numbers +2000-2063 to identify GPIO lines in a bank of I2C GPIO expanders. Controller Drivers: gpio_chip ============================= In the gpiolib framework each GPIO controller is packaged as a "struct -gpio_chip" (see linux/gpio/driver.h for its complete definition) with members -common to each controller of that type: +gpio_chip" (see <linux/gpio/driver.h> for its complete definition) with members +common to each controller of that type, these should be assigned by the +driver code: - methods to establish GPIO line direction - methods used to access GPIO line values @@ -48,12 +63,12 @@ common to each controller of that type: - method to return the IRQ number associated to a given GPIO line - flag saying whether calls to its methods may sleep - optional line names array to identify lines - - optional debugfs dump method (showing extra state like pullup config) + - optional debugfs dump method (showing extra state information) - optional base number (will be automatically assigned if omitted) - optional label for diagnostics and GPIO chip mapping using platform data The code implementing a gpio_chip should support multiple instances of the -controller, possibly using the driver model. That code will configure each +controller, preferably using the driver model. That code will configure each gpio_chip and issue ``gpiochip_add[_data]()`` or ``devm_gpiochip_add_data()``. Removing a GPIO controller should be rare; use ``[devm_]gpiochip_remove()`` when it is unavoidable. @@ -62,24 +77,28 @@ Often a gpio_chip is part of an instance-specific structure with states not exposed by the GPIO interfaces, such as addressing, power management, and more. Chips such as audio codecs will have complex non-GPIO states. -Any debugfs dump method should normally ignore signals which haven't been -requested as GPIOs. They can use gpiochip_is_requested(), which returns either -NULL or the label associated with that GPIO when it was requested. +Any debugfs dump method should normally ignore lines which haven't been +requested. They can use gpiochip_is_requested(), which returns either +NULL or the label associated with that GPIO line when it was requested. -RT_FULL: the GPIO driver should not use spinlock_t or any sleepable APIs -(like PM runtime) in its gpio_chip implementation (.get/.set and direction -control callbacks) if it is expected to call GPIO APIs from atomic context -on -RT (inside hard IRQ handlers and similar contexts). Normally this should -not be required. +Realtime considerations: the GPIO driver should not use spinlock_t or any +sleepable APIs (like PM runtime) in its gpio_chip implementation (.get/.set +and direction control callbacks) if it is expected to call GPIO APIs from +atomic context on realtime kernels (inside hard IRQ handlers and similar +contexts). Normally this should not be required. GPIO electrical configuration ----------------------------- -GPIOs can be configured for several electrical modes of operation by using the -.set_config() callback. Currently this API supports setting debouncing and -single-ended modes (open drain/open source). These settings are described -below. +GPIO lines can be configured for several electrical modes of operation by using +the .set_config() callback. Currently this API supports setting: + +- Debouncing +- Single-ended modes (open drain/open source) +- Pull up and pull down resistor enablement + +These settings are described below. The .set_config() callback uses the same enumerators and configuration semantics as the generic pin control drivers. This is not a coincidence: it is @@ -94,8 +113,8 @@ description needs to provide "GPIO ranges" mapping the GPIO line offsets to pin numbers on the pin controller so they can properly cross-reference each other. -GPIOs with debounce support ---------------------------- +GPIO lines with debounce support +-------------------------------- Debouncing is a configuration set to a pin indicating that it is connected to a mechanical switch or button, or similar that may bounce. Bouncing means the @@ -111,8 +130,8 @@ a certain number of milliseconds for debouncing, or just "on/off" if that time is not configurable. -GPIOs with open drain/source support ------------------------------------- +GPIO lines with open drain/source support +----------------------------------------- Open drain (CMOS) or open collector (TTL) means the line is not actively driven high: instead you provide the drain/collector as output, so when the transistor @@ -132,13 +151,13 @@ This configuration is normally used as a way to achieve one of two things: - Level-shifting: to reach a logical level higher than that of the silicon where the output resides. -- inverse wire-OR on an I/O line, for example a GPIO line, making it possible +- Inverse wire-OR on an I/O line, for example a GPIO line, making it possible for any driving stage on the line to drive it low even if any other output to the same line is simultaneously driving it high. A special case of this is driving the SCL and SDA lines of an I2C bus, which is by definition a wire-OR bus. -Both usecases require that the line be equipped with a pull-up resistor. This +Both use cases require that the line be equipped with a pull-up resistor. This resistor will make the line tend to high level unless one of the transistors on the rail actively pulls it down. @@ -208,27 +227,91 @@ For open source configuration the same principle is used, just that instead of actively driving the line low, it is set to input. +GPIO lines with pull up/down resistor support +--------------------------------------------- + +A GPIO line can support pull-up/down using the .set_config() callback. This +means that a pull up or pull-down resistor is available on the output of the +GPIO line, and this resistor is software controlled. + +In discrete designs, a pull-up or pull-down resistor is simply soldered on +the circuit board. This is not something we deal or model in software. The +most you will think about these lines is that they will very likely be +configured as open drain or open source (see the section above). + +The .set_config() callback can only turn pull up or down on and off, and will +no have any semantic knowledge about the resistance used. It will only say +switch a bit in a register enabling or disabling pull-up or pull-down. + +If the GPIO line supports shunting in different resistance values for the +pull-up or pull-down resistor, the GPIO chip callback .set_config() will not +suffice. For these complex use cases, a combined GPIO chip and pin controller +need to be implemented, as the pin config interface of a pin controller +supports more versatile control over electrical properties and can handle +different pull-up or pull-down resistance values. + + GPIO drivers providing IRQs ---------------------------- +=========================== + It is custom that GPIO drivers (GPIO chips) are also providing interrupts, most often cascaded off a parent interrupt controller, and in some special cases the GPIO logic is melded with a SoC's primary interrupt controller. -The IRQ portions of the GPIO block are implemented using an irqchip, using +The IRQ portions of the GPIO block are implemented using an irq_chip, using the header <linux/irq.h>. So basically such a driver is utilizing two sub- systems simultaneously: gpio and irq. -RT_FULL: a realtime compliant GPIO driver should not use spinlock_t or any -sleepable APIs (like PM runtime) as part of its irq_chip implementation. +It is legal for any IRQ consumer to request an IRQ from any irqchip even if it +is a combined GPIO+IRQ driver. The basic premise is that gpio_chip and +irq_chip are orthogonal, and offering their services independent of each +other. -* spinlock_t should be replaced with raw_spinlock_t [1]. -* If sleepable APIs have to be used, these can be done from the .irq_bus_lock() +gpiod_to_irq() is just a convenience function to figure out the IRQ for a +certain GPIO line and should not be relied upon to have been called before +the IRQ is used. + +Always prepare the hardware and make it ready for action in respective +callbacks from the GPIO and irq_chip APIs. Do not rely on gpiod_to_irq() having +been called first. + +We can divide GPIO irqchips in two broad categories: + +- CASCADED INTERRUPT CHIPS: this means that the GPIO chip has one common + interrupt output line, which is triggered by any enabled GPIO line on that + chip. The interrupt output line will then be routed to an parent interrupt + controller one level up, in the most simple case the systems primary + interrupt controller. This is modeled by an irqchip that will inspect bits + inside the GPIO controller to figure out which line fired it. The irqchip + part of the driver needs to inspect registers to figure this out and it + will likely also need to acknowledge that it is handling the interrupt + by clearing some bit (sometime implicitly, by just reading a status + register) and it will often need to set up the configuration such as + edge sensitivity (rising or falling edge, or high/low level interrupt for + example). + +- HIERARCHICAL INTERRUPT CHIPS: this means that each GPIO line has a dedicated + irq line to a parent interrupt controller one level up. There is no need + to inquire the GPIO hardware to figure out which line has figured, but it + may still be necessary to acknowledge the interrupt and set up the + configuration such as edge sensitivity. + +Realtime considerations: a realtime compliant GPIO driver should not use +spinlock_t or any sleepable APIs (like PM runtime) as part of its irqchip +implementation. + +- spinlock_t should be replaced with raw_spinlock_t [1]. +- If sleepable APIs have to be used, these can be done from the .irq_bus_lock() and .irq_bus_unlock() callbacks, as these are the only slowpath callbacks on an irqchip. Create the callbacks if needed [2]. -GPIO irqchips usually fall in one of two categories: -* CHAINED GPIO irqchips: these are usually the type that is embedded on +Cascaded GPIO irqchips +---------------------- + +Cascaded GPIO irqchips usually fall in one of three categories: + +- CHAINED CASCADED GPIO IRQCHIPS: these are usually the type that is embedded on an SoC. This means that there is a fast IRQ flow handler for the GPIOs that gets called in a chain from the parent IRQ handler, most typically the system interrupt controller. This means that the GPIO irqchip handler will @@ -245,16 +328,19 @@ GPIO irqchips usually fall in one of two categories: struct gpio_chip, as everything happens directly in the callbacks: no slow bus traffic like I2C can be used. - RT_FULL: Note, chained IRQ handlers will not be forced threaded on -RT. - As result, spinlock_t or any sleepable APIs (like PM runtime) can't be used - in chained IRQ handler. - If required (and if it can't be converted to the nested threaded GPIO irqchip) - a chained IRQ handler can be converted to generic irq handler and this way - it will be a threaded IRQ handler on -RT and a hard IRQ handler on non-RT - (for example, see [3]). - Know W/A: The generic_handle_irq() is expected to be called with IRQ disabled, + Realtime considerations: Note that chained IRQ handlers will not be forced + threaded on -RT. As a result, spinlock_t or any sleepable APIs (like PM + runtime) can't be used in a chained IRQ handler. + + If required (and if it can't be converted to the nested threaded GPIO irqchip, + see below) a chained IRQ handler can be converted to generic irq handler and + this way it will become a threaded IRQ handler on -RT and a hard IRQ handler + on non-RT (for example, see [3]). + + The generic_handle_irq() is expected to be called with IRQ disabled, so the IRQ core will complain if it is called from an IRQ handler which is - forced to a thread. The "fake?" raw lock can be used to W/A this problem:: + forced to a thread. The "fake?" raw lock can be used to work around this + problem:: raw_spinlock_t wa_lock; static irqreturn_t omap_gpio_irq_handler(int irq, void *gpiobank) @@ -263,7 +349,7 @@ GPIO irqchips usually fall in one of two categories: generic_handle_irq(irq_find_mapping(bank->chip.irq.domain, bit)); raw_spin_unlock_irqrestore(&bank->wa_lock, wa_lock_flags); -* GENERIC CHAINED GPIO irqchips: these are the same as "CHAINED GPIO irqchips", +- GENERIC CHAINED GPIO IRQCHIPS: these are the same as "CHAINED GPIO irqchips", but chained IRQ handlers are not used. Instead GPIO IRQs dispatching is performed by generic IRQ handler which is configured using request_irq(). The GPIO irqchip will then end up calling something like this sequence in @@ -273,16 +359,19 @@ GPIO irqchips usually fall in one of two categories: for each detected GPIO IRQ generic_handle_irq(...); - RT_FULL: Such kind of handlers will be forced threaded on -RT, as result IRQ - core will complain that generic_handle_irq() is called with IRQ enabled and - the same W/A as for "CHAINED GPIO irqchips" can be applied. + Realtime considerations: this kind of handlers will be forced threaded on -RT, + and as result the IRQ core will complain that generic_handle_irq() is called + with IRQ enabled and the same work around as for "CHAINED GPIO irqchips" can + be applied. + +- NESTED THREADED GPIO IRQCHIPS: these are off-chip GPIO expanders and any + other GPIO irqchip residing on the other side of a sleeping bus such as I2C + or SPI. -* NESTED THREADED GPIO irqchips: these are off-chip GPIO expanders and any - other GPIO irqchip residing on the other side of a sleeping bus. Of course - such drivers that need slow bus traffic to read out IRQ status and similar, - traffic which may in turn incur other IRQs to happen, cannot be handled - in a quick IRQ handler with IRQs disabled. Instead they need to spawn a - thread and then mask the parent IRQ line until the interrupt is handled + Of course such drivers that need slow bus traffic to read out IRQ status and + similar, traffic which may in turn incur other IRQs to happen, cannot be + handled in a quick IRQ handler with IRQs disabled. Instead they need to spawn + a thread and then mask the parent IRQ line until the interrupt is handled by the driver. The hallmark of this driver is to call something like this in its interrupt handler:: @@ -294,36 +383,46 @@ GPIO irqchips usually fall in one of two categories: flag on struct gpio_chip to true, indicating that this chip may sleep when accessing the GPIOs. + These kinds of irqchips are inherently realtime tolerant as they are + already set up to handle sleeping contexts. + + +Infrastructure helpers for GPIO irqchips +---------------------------------------- + To help out in handling the set-up and management of GPIO irqchips and the associated irqdomain and resource allocation callbacks, the gpiolib has some helpers that can be enabled by selecting the GPIOLIB_IRQCHIP Kconfig symbol: -* gpiochip_irqchip_add(): adds a chained irqchip to a gpiochip. It will pass - the struct gpio_chip* for the chip to all IRQ callbacks, so the callbacks - need to embed the gpio_chip in its state container and obtain a pointer - to the container using container_of(). +- gpiochip_irqchip_add(): adds a chained cascaded irqchip to a gpiochip. It + will pass the struct gpio_chip* for the chip to all IRQ callbacks, so the + callbacks need to embed the gpio_chip in its state container and obtain a + pointer to the container using container_of(). (See Documentation/driver-model/design-patterns.txt) -* gpiochip_irqchip_add_nested(): adds a nested irqchip to a gpiochip. +- gpiochip_irqchip_add_nested(): adds a nested cascaded irqchip to a gpiochip, + as discussed above regarding different types of cascaded irqchips. The + cascaded irq has to be handled by a threaded interrupt handler. Apart from that it works exactly like the chained irqchip. -* gpiochip_set_chained_irqchip(): sets up a chained irq handler for a +- gpiochip_set_chained_irqchip(): sets up a chained cascaded irq handler for a gpio_chip from a parent IRQ and passes the struct gpio_chip* as handler - data. (Notice handler data, since the irqchip data is likely used by the - parent irqchip!). + data. Notice that we pass is as the handler data, since the irqchip data is + likely used by the parent irqchip. -* gpiochip_set_nested_irqchip(): sets up a nested irq handler for a +- gpiochip_set_nested_irqchip(): sets up a nested cascaded irq handler for a gpio_chip from a parent IRQ. As the parent IRQ has usually been explicitly requested by the driver, this does very little more than mark all the child IRQs as having the other IRQ as parent. -If there is a need to exclude certain GPIOs from the IRQ domain, you can -set .irq.need_valid_mask of the gpiochip before gpiochip_add_data() is -called. This allocates an .irq.valid_mask with as many bits set as there -are GPIOs in the chip. Drivers can exclude GPIOs by clearing bits from this -mask. The mask must be filled in before gpiochip_irqchip_add() or -gpiochip_irqchip_add_nested() is called. +If there is a need to exclude certain GPIO lines from the IRQ domain handled by +these helpers, we can set .irq.need_valid_mask of the gpiochip before +[devm_]gpiochip_add_data() is called. This allocates an .irq.valid_mask with as +many bits set as there are GPIO lines in the chip, each bit representing line +0..n-1. Drivers can exclude GPIO lines by clearing bits from this mask. The mask +must be filled in before gpiochip_irqchip_add() or gpiochip_irqchip_add_nested() +is called. To use the helpers please keep the following in mind: @@ -333,33 +432,24 @@ To use the helpers please keep the following in mind: - Nominally set all handlers to handle_bad_irq() in the setup call and pass handle_bad_irq() as flow handler parameter in gpiochip_irqchip_add() if it is - expected for GPIO driver that irqchip .set_type() callback have to be called - before using/enabling GPIO IRQ. Then set the handler to handle_level_irq() - and/or handle_edge_irq() in the irqchip .set_type() callback depending on - what your controller supports. + expected for GPIO driver that irqchip .set_type() callback will be called + before using/enabling each GPIO IRQ. Then set the handler to + handle_level_irq() and/or handle_edge_irq() in the irqchip .set_type() + callback depending on what your controller supports and what is requested + by the consumer. -It is legal for any IRQ consumer to request an IRQ from any irqchip no matter -if that is a combined GPIO+IRQ driver. The basic premise is that gpio_chip and -irq_chip are orthogonal, and offering their services independent of each -other. - -gpiod_to_irq() is just a convenience function to figure out the IRQ for a -certain GPIO line and should not be relied upon to have been called before -the IRQ is used. -So always prepare the hardware and make it ready for action in respective -callbacks from the GPIO and irqchip APIs. Do not rely on gpiod_to_irq() having -been called first. +Locking IRQ usage +----------------- -This orthogonality leads to ambiguities that we need to solve: if there is -competition inside the subsystem which side is using the resource (a certain -GPIO line and register for example) it needs to deny certain operations and -keep track of usage inside of the gpiolib subsystem. This is why the API -below exists. +Since GPIO and irq_chip are orthogonal, we can get conflicts between different +use cases. For example a GPIO line used for IRQs should be an input line, +it does not make sense to fire interrupts on an output GPIO. +If there is competition inside the subsystem which side is using the +resource (a certain GPIO line and register for example) it needs to deny +certain operations and keep track of usage inside of the gpiolib subsystem. -Locking IRQ usage ------------------ Input GPIOs can be used as IRQ signals. When this happens, a driver is requested to mark the GPIO as being used as an IRQ:: @@ -380,9 +470,15 @@ assigned. Disabling and enabling IRQs --------------------------- + +In some (fringe) use cases, a driver may be using a GPIO line as input for IRQs, +but occasionally switch that line over to drive output and then back to being +an input with interrupts again. This happens on things like CEC (Consumer +Electronics Control). + When a GPIO is used as an IRQ signal, then gpiolib also needs to know if the IRQ is enabled or disabled. In order to inform gpiolib about this, -a driver should call:: +the irqchip driver should call:: void gpiochip_disable_irq(struct gpio_chip *chip, unsigned int offset) @@ -398,40 +494,45 @@ irqchip. When using the gpiolib irqchip helpers, these callbacks are automatically assigned. + Real-Time compliance for GPIO IRQ chips --------------------------------------- -Any provider of irqchips needs to be carefully tailored to support Real Time +Any provider of irqchips needs to be carefully tailored to support Real-Time preemption. It is desirable that all irqchips in the GPIO subsystem keep this in mind and do the proper testing to assure they are real time-enabled. -So, pay attention on above " RT_FULL:" notes, please. -The following is a checklist to follow when preparing a driver for real -time-compliance: -- ensure spinlock_t is not used as part irq_chip implementation; -- ensure that sleepable APIs are not used as part irq_chip implementation. +So, pay attention on above realtime considerations in the documentation. + +The following is a checklist to follow when preparing a driver for real-time +compliance: + +- ensure spinlock_t is not used as part irq_chip implementation +- ensure that sleepable APIs are not used as part irq_chip implementation If sleepable APIs have to be used, these can be done from the .irq_bus_lock() - and .irq_bus_unlock() callbacks; + and .irq_bus_unlock() callbacks - Chained GPIO irqchips: ensure spinlock_t or any sleepable APIs are not used - from chained IRQ handler; + from the chained IRQ handler - Generic chained GPIO irqchips: take care about generic_handle_irq() calls and - apply corresponding W/A; -- Chained GPIO irqchips: get rid of chained IRQ handler and use generic irq - handler if possible :) -- regmap_mmio: Sry, but you are in trouble :( if MMIO regmap is used as for - GPIO IRQ chip implementation; -- Test your driver with the appropriate in-kernel real time test cases for both - level and edge IRQs. + apply corresponding work-around +- Chained GPIO irqchips: get rid of the chained IRQ handler and use generic irq + handler if possible +- regmap_mmio: it is possible to disable internal locking in regmap by setting + .disable_locking and handling the locking in the GPIO driver +- Test your driver with the appropriate in-kernel real-time test cases for both + level and edge IRQs + +* [1] http://www.spinics.net/lists/linux-omap/msg120425.html +* [2] https://lkml.org/lkml/2015/9/25/494 +* [3] https://lkml.org/lkml/2015/9/25/495 Requesting self-owned GPIO pins -------------------------------- +=============================== Sometimes it is useful to allow a GPIO chip driver to request its own GPIO -descriptors through the gpiolib API. Using gpio_request() for this purpose -does not help since it pins the module to the kernel forever (it calls -try_module_get()). A GPIO driver can use the following functions instead -to request and free descriptors without being pinned to the kernel forever:: +descriptors through the gpiolib API. A GPIO driver can use the following +functions to request and free descriptors:: struct gpio_desc *gpiochip_request_own_desc(struct gpio_desc *desc, u16 hwnum, @@ -446,7 +547,3 @@ gpiochip_free_own_desc(). These functions must be used with care since they do not affect module use count. Do not use the functions to request gpio descriptors not owned by the calling driver. - -* [1] http://www.spinics.net/lists/linux-omap/msg120425.html -* [2] https://lkml.org/lkml/2015/9/25/494 -* [3] https://lkml.org/lkml/2015/9/25/495 diff --git a/Documentation/driver-api/index.rst b/Documentation/driver-api/index.rst index c0b600ed9961..d26308af6036 100644 --- a/Documentation/driver-api/index.rst +++ b/Documentation/driver-api/index.rst @@ -56,6 +56,8 @@ available subsections can be seen below. slimbus soundwire/index fpga/index + acpi/index + generic-counter .. only:: subproject and html diff --git a/Documentation/driver-api/pci/p2pdma.rst b/Documentation/driver-api/pci/p2pdma.rst index 6d85b5a2598d..44deb52beeb4 100644 --- a/Documentation/driver-api/pci/p2pdma.rst +++ b/Documentation/driver-api/pci/p2pdma.rst @@ -132,10 +132,6 @@ precludes passing these pages to userspace. P2P memory is also technically IO memory but should never have any side effects behind it. Thus, the order of loads and stores should not be important and ioreadX(), iowriteX() and friends should not be necessary. -However, as the memory is not cache coherent, if access ever needs to -be protected by a spinlock then :c:func:`mmiowb()` must be used before -unlocking the lock. (See ACQUIRES VS I/O ACCESSES in -Documentation/memory-barriers.txt) P2P DMA Support Library diff --git a/Documentation/driver-api/pm/cpuidle.rst b/Documentation/driver-api/pm/cpuidle.rst index 5842ab621a58..006cf6db40c6 100644 --- a/Documentation/driver-api/pm/cpuidle.rst +++ b/Documentation/driver-api/pm/cpuidle.rst @@ -1,3 +1,6 @@ +.. SPDX-License-Identifier: GPL-2.0 +.. include:: <isonum.txt> + .. |struct cpuidle_governor| replace:: :c:type:`struct cpuidle_governor <cpuidle_governor>` .. |struct cpuidle_device| replace:: :c:type:`struct cpuidle_device <cpuidle_device>` .. |struct cpuidle_driver| replace:: :c:type:`struct cpuidle_driver <cpuidle_driver>` @@ -7,9 +10,9 @@ CPU Idle Time Management ======================== -:: +:Copyright: |copy| 2019 Intel Corporation - Copyright (c) 2019 Intel Corp., Rafael J. Wysocki <rafael.j.wysocki@intel.com> +:Author: Rafael J. Wysocki <rafael.j.wysocki@intel.com> CPU Idle Time Management Subsystem diff --git a/Documentation/driver-api/pm/devices.rst b/Documentation/driver-api/pm/devices.rst index 090c151aa86b..30835683616a 100644 --- a/Documentation/driver-api/pm/devices.rst +++ b/Documentation/driver-api/pm/devices.rst @@ -1,3 +1,6 @@ +.. SPDX-License-Identifier: GPL-2.0 +.. include:: <isonum.txt> + .. |struct dev_pm_ops| replace:: :c:type:`struct dev_pm_ops <dev_pm_ops>` .. |struct dev_pm_domain| replace:: :c:type:`struct dev_pm_domain <dev_pm_domain>` .. |struct bus_type| replace:: :c:type:`struct bus_type <bus_type>` @@ -12,11 +15,12 @@ Device Power Management Basics ============================== -:: +:Copyright: |copy| 2010-2011 Rafael J. Wysocki <rjw@sisk.pl>, Novell Inc. +:Copyright: |copy| 2010 Alan Stern <stern@rowland.harvard.edu> +:Copyright: |copy| 2016 Intel Corporation + +:Author: Rafael J. Wysocki <rafael.j.wysocki@intel.com> - Copyright (c) 2010-2011 Rafael J. Wysocki <rjw@sisk.pl>, Novell Inc. - Copyright (c) 2010 Alan Stern <stern@rowland.harvard.edu> - Copyright (c) 2016 Intel Corp., Rafael J. Wysocki <rafael.j.wysocki@intel.com> Most of the code in Linux is device drivers, so most of the Linux power management (PM) code is also driver-specific. Most drivers will do very diff --git a/Documentation/driver-api/pm/index.rst b/Documentation/driver-api/pm/index.rst index 56975c6bc789..c2a9ef8d115c 100644 --- a/Documentation/driver-api/pm/index.rst +++ b/Documentation/driver-api/pm/index.rst @@ -1,3 +1,5 @@ +.. SPDX-License-Identifier: GPL-2.0 + =============================== CPU and Device Power Management =============================== diff --git a/Documentation/driver-api/pm/notifiers.rst b/Documentation/driver-api/pm/notifiers.rst index 62f860026992..186435c43b77 100644 --- a/Documentation/driver-api/pm/notifiers.rst +++ b/Documentation/driver-api/pm/notifiers.rst @@ -1,10 +1,14 @@ +.. SPDX-License-Identifier: GPL-2.0 +.. include:: <isonum.txt> + ============================= Suspend/Hibernation Notifiers ============================= -:: +:Copyright: |copy| 2016 Intel Corporation + +:Author: Rafael J. Wysocki <rafael.j.wysocki@intel.com> - Copyright (c) 2016 Intel Corp., Rafael J. Wysocki <rafael.j.wysocki@intel.com> There are some operations that subsystems or drivers may want to carry out before hibernation/suspend or after restore/resume, but they require the system diff --git a/Documentation/driver-api/pm/types.rst b/Documentation/driver-api/pm/types.rst index 3ebdecc54104..73a231caf764 100644 --- a/Documentation/driver-api/pm/types.rst +++ b/Documentation/driver-api/pm/types.rst @@ -1,3 +1,5 @@ +.. SPDX-License-Identifier: GPL-2.0 + ================================== Device Power Management Data Types ================================== diff --git a/Documentation/driver-api/soundwire/stream.rst b/Documentation/driver-api/soundwire/stream.rst index 26a6064503fd..5351bd2f34a8 100644 --- a/Documentation/driver-api/soundwire/stream.rst +++ b/Documentation/driver-api/soundwire/stream.rst @@ -201,7 +201,7 @@ Bus implements below API for allocate a stream which needs to be called once per stream. From ASoC DPCM framework, this stream state maybe linked to .startup() operation. - .. code-block:: c +.. code-block:: c int sdw_alloc_stream(char * stream_name); @@ -228,7 +228,7 @@ the respective Master(s) and Slave(s) associated with stream. These APIs can only be invoked once by respective Master(s) and Slave(s). From ASoC DPCM framework, this stream state is linked to .hw_params() operation. - .. code-block:: c +.. code-block:: c int sdw_stream_add_master(struct sdw_bus * bus, struct sdw_stream_config * stream_config, @@ -274,7 +274,7 @@ Bus implements below API for PREPARE state which needs to be called once per stream. From ASoC DPCM framework, this stream state is linked to .prepare() operation. - .. code-block:: c +.. code-block:: c int sdw_prepare_stream(struct sdw_stream_runtime * stream); @@ -304,7 +304,7 @@ Bus implements below API for ENABLE state which needs to be called once per stream. From ASoC DPCM framework, this stream state is linked to .trigger() start operation. - .. code-block:: c +.. code-block:: c int sdw_enable_stream(struct sdw_stream_runtime * stream); @@ -332,7 +332,7 @@ Bus implements below API for DISABLED state which needs to be called once per stream. From ASoC DPCM framework, this stream state is linked to .trigger() stop operation. - .. code-block:: c +.. code-block:: c int sdw_disable_stream(struct sdw_stream_runtime * stream); @@ -357,7 +357,7 @@ Bus implements below API for DEPREPARED state which needs to be called once per stream. From ASoC DPCM framework, this stream state is linked to .trigger() stop operation. - .. code-block:: c +.. code-block:: c int sdw_deprepare_stream(struct sdw_stream_runtime * stream); @@ -382,7 +382,7 @@ Bus implements below APIs for RELEASE state which needs to be called by all the Master(s) and Slave(s) associated with stream. From ASoC DPCM framework, this stream state is linked to .hw_free() operation. - .. code-block:: c +.. code-block:: c int sdw_stream_remove_master(struct sdw_bus * bus, struct sdw_stream_runtime * stream); @@ -395,7 +395,7 @@ stream assigned as part of ALLOCATED state. In .shutdown() the data structure maintaining stream state are freed up. - .. code-block:: c +.. code-block:: c void sdw_release_stream(struct sdw_stream_runtime * stream); diff --git a/Documentation/driver-api/uio-howto.rst b/Documentation/driver-api/uio-howto.rst index 25f50eace28b..8fecfa11d4ff 100644 --- a/Documentation/driver-api/uio-howto.rst +++ b/Documentation/driver-api/uio-howto.rst @@ -276,8 +276,8 @@ fields of ``struct uio_mem``: - ``int memtype``: Required if the mapping is used. Set this to ``UIO_MEM_PHYS`` if you you have physical memory on your card to be mapped. Use ``UIO_MEM_LOGICAL`` for logical memory (e.g. allocated - with :c:func:`kmalloc()`). There's also ``UIO_MEM_VIRTUAL`` for - virtual memory. + with :c:func:`__get_free_pages()` but not kmalloc()). There's also + ``UIO_MEM_VIRTUAL`` for virtual memory. - ``phys_addr_t addr``: Required if the mapping is used. Fill in the address of your memory block. This address is the one that appears in |