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diff --git a/Documentation/PCI/pcieaer-howto.txt b/Documentation/PCI/pcieaer-howto.txt deleted file mode 100644 index 48ce7903e3c6..000000000000 --- a/Documentation/PCI/pcieaer-howto.txt +++ /dev/null @@ -1,267 +0,0 @@ - The PCI Express Advanced Error Reporting Driver Guide HOWTO - T. Long Nguyen <tom.l.nguyen@intel.com> - Yanmin Zhang <yanmin.zhang@intel.com> - 07/29/2006 - - -1. Overview - -1.1 About this guide - -This guide describes the basics of the PCI Express Advanced Error -Reporting (AER) driver and provides information on how to use it, as -well as how to enable the drivers of endpoint devices to conform with -PCI Express AER driver. - -1.2 Copyright (C) Intel Corporation 2006. - -1.3 What is the PCI Express AER Driver? - -PCI Express error signaling can occur on the PCI Express link itself -or on behalf of transactions initiated on the link. PCI Express -defines two error reporting paradigms: the baseline capability and -the Advanced Error Reporting capability. The baseline capability is -required of all PCI Express components providing a minimum defined -set of error reporting requirements. Advanced Error Reporting -capability is implemented with a PCI Express advanced error reporting -extended capability structure providing more robust error reporting. - -The PCI Express AER driver provides the infrastructure to support PCI -Express Advanced Error Reporting capability. The PCI Express AER -driver provides three basic functions: - -- Gathers the comprehensive error information if errors occurred. -- Reports error to the users. -- Performs error recovery actions. - -AER driver only attaches root ports which support PCI-Express AER -capability. - - -2. User Guide - -2.1 Include the PCI Express AER Root Driver into the Linux Kernel - -The PCI Express AER Root driver is a Root Port service driver attached -to the PCI Express Port Bus driver. If a user wants to use it, the driver -has to be compiled. Option CONFIG_PCIEAER supports this capability. It -depends on CONFIG_PCIEPORTBUS, so pls. set CONFIG_PCIEPORTBUS=y and -CONFIG_PCIEAER = y. - -2.2 Load PCI Express AER Root Driver - -Some systems have AER support in firmware. Enabling Linux AER support at -the same time the firmware handles AER may result in unpredictable -behavior. Therefore, Linux does not handle AER events unless the firmware -grants AER control to the OS via the ACPI _OSC method. See the PCI FW 3.0 -Specification for details regarding _OSC usage. - -2.3 AER error output - -When a PCIe AER error is captured, an error message will be output to -console. If it's a correctable error, it is output as a warning. -Otherwise, it is printed as an error. So users could choose different -log level to filter out correctable error messages. - -Below shows an example: -0000:50:00.0: PCIe Bus Error: severity=Uncorrected (Fatal), type=Transaction Layer, id=0500(Requester ID) -0000:50:00.0: device [8086:0329] error status/mask=00100000/00000000 -0000:50:00.0: [20] Unsupported Request (First) -0000:50:00.0: TLP Header: 04000001 00200a03 05010000 00050100 - -In the example, 'Requester ID' means the ID of the device who sends -the error message to root port. Pls. refer to pci express specs for -other fields. - -2.4 AER Statistics / Counters - -When PCIe AER errors are captured, the counters / statistics are also exposed -in the form of sysfs attributes which are documented at -Documentation/ABI/testing/sysfs-bus-pci-devices-aer_stats - -3. Developer Guide - -To enable AER aware support requires a software driver to configure -the AER capability structure within its device and to provide callbacks. - -To support AER better, developers need understand how AER does work -firstly. - -PCI Express errors are classified into two types: correctable errors -and uncorrectable errors. This classification is based on the impacts -of those errors, which may result in degraded performance or function -failure. - -Correctable errors pose no impacts on the functionality of the -interface. The PCI Express protocol can recover without any software -intervention or any loss of data. These errors are detected and -corrected by hardware. Unlike correctable errors, uncorrectable -errors impact functionality of the interface. Uncorrectable errors -can cause a particular transaction or a particular PCI Express link -to be unreliable. Depending on those error conditions, uncorrectable -errors are further classified into non-fatal errors and fatal errors. -Non-fatal errors cause the particular transaction to be unreliable, -but the PCI Express link itself is fully functional. Fatal errors, on -the other hand, cause the link to be unreliable. - -When AER is enabled, a PCI Express device will automatically send an -error message to the PCIe root port above it when the device captures -an error. The Root Port, upon receiving an error reporting message, -internally processes and logs the error message in its PCI Express -capability structure. Error information being logged includes storing -the error reporting agent's requestor ID into the Error Source -Identification Registers and setting the error bits of the Root Error -Status Register accordingly. If AER error reporting is enabled in Root -Error Command Register, the Root Port generates an interrupt if an -error is detected. - -Note that the errors as described above are related to the PCI Express -hierarchy and links. These errors do not include any device specific -errors because device specific errors will still get sent directly to -the device driver. - -3.1 Configure the AER capability structure - -AER aware drivers of PCI Express component need change the device -control registers to enable AER. They also could change AER registers, -including mask and severity registers. Helper function -pci_enable_pcie_error_reporting could be used to enable AER. See -section 3.3. - -3.2. Provide callbacks - -3.2.1 callback reset_link to reset pci express link - -This callback is used to reset the pci express physical link when a -fatal error happens. The root port aer service driver provides a -default reset_link function, but different upstream ports might -have different specifications to reset pci express link, so all -upstream ports should provide their own reset_link functions. - -In struct pcie_port_service_driver, a new pointer, reset_link, is -added. - -pci_ers_result_t (*reset_link) (struct pci_dev *dev); - -Section 3.2.2.2 provides more detailed info on when to call -reset_link. - -3.2.2 PCI error-recovery callbacks - -The PCI Express AER Root driver uses error callbacks to coordinate -with downstream device drivers associated with a hierarchy in question -when performing error recovery actions. - -Data struct pci_driver has a pointer, err_handler, to point to -pci_error_handlers who consists of a couple of callback function -pointers. AER driver follows the rules defined in -pci-error-recovery.txt except pci express specific parts (e.g. -reset_link). Pls. refer to pci-error-recovery.txt for detailed -definitions of the callbacks. - -Below sections specify when to call the error callback functions. - -3.2.2.1 Correctable errors - -Correctable errors pose no impacts on the functionality of -the interface. The PCI Express protocol can recover without any -software intervention or any loss of data. These errors do not -require any recovery actions. The AER driver clears the device's -correctable error status register accordingly and logs these errors. - -3.2.2.2 Non-correctable (non-fatal and fatal) errors - -If an error message indicates a non-fatal error, performing link reset -at upstream is not required. The AER driver calls error_detected(dev, -pci_channel_io_normal) to all drivers associated within a hierarchy in -question. for example, -EndPoint<==>DownstreamPort B<==>UpstreamPort A<==>RootPort. -If Upstream port A captures an AER error, the hierarchy consists of -Downstream port B and EndPoint. - -A driver may return PCI_ERS_RESULT_CAN_RECOVER, -PCI_ERS_RESULT_DISCONNECT, or PCI_ERS_RESULT_NEED_RESET, depending on -whether it can recover or the AER driver calls mmio_enabled as next. - -If an error message indicates a fatal error, kernel will broadcast -error_detected(dev, pci_channel_io_frozen) to all drivers within -a hierarchy in question. Then, performing link reset at upstream is -necessary. As different kinds of devices might use different approaches -to reset link, AER port service driver is required to provide the -function to reset link. Firstly, kernel looks for if the upstream -component has an aer driver. If it has, kernel uses the reset_link -callback of the aer driver. If the upstream component has no aer driver -and the port is downstream port, we will perform a hot reset as the -default by setting the Secondary Bus Reset bit of the Bridge Control -register associated with the downstream port. As for upstream ports, -they should provide their own aer service drivers with reset_link -function. If error_detected returns PCI_ERS_RESULT_CAN_RECOVER and -reset_link returns PCI_ERS_RESULT_RECOVERED, the error handling goes -to mmio_enabled. - -3.3 helper functions - -3.3.1 int pci_enable_pcie_error_reporting(struct pci_dev *dev); -pci_enable_pcie_error_reporting enables the device to send error -messages to root port when an error is detected. Note that devices -don't enable the error reporting by default, so device drivers need -call this function to enable it. - -3.3.2 int pci_disable_pcie_error_reporting(struct pci_dev *dev); -pci_disable_pcie_error_reporting disables the device to send error -messages to root port when an error is detected. - -3.3.3 int pci_cleanup_aer_uncorrect_error_status(struct pci_dev *dev); -pci_cleanup_aer_uncorrect_error_status cleanups the uncorrectable -error status register. - -3.4 Frequent Asked Questions - -Q: What happens if a PCI Express device driver does not provide an -error recovery handler (pci_driver->err_handler is equal to NULL)? - -A: The devices attached with the driver won't be recovered. If the -error is fatal, kernel will print out warning messages. Please refer -to section 3 for more information. - -Q: What happens if an upstream port service driver does not provide -callback reset_link? - -A: Fatal error recovery will fail if the errors are reported by the -upstream ports who are attached by the service driver. - -Q: How does this infrastructure deal with driver that is not PCI -Express aware? - -A: This infrastructure calls the error callback functions of the -driver when an error happens. But if the driver is not aware of -PCI Express, the device might not report its own errors to root -port. - -Q: What modifications will that driver need to make it compatible -with the PCI Express AER Root driver? - -A: It could call the helper functions to enable AER in devices and -cleanup uncorrectable status register. Pls. refer to section 3.3. - - -4. Software error injection - -Debugging PCIe AER error recovery code is quite difficult because it -is hard to trigger real hardware errors. Software based error -injection can be used to fake various kinds of PCIe errors. - -First you should enable PCIe AER software error injection in kernel -configuration, that is, following item should be in your .config. - -CONFIG_PCIEAER_INJECT=y or CONFIG_PCIEAER_INJECT=m - -After reboot with new kernel or insert the module, a device file named -/dev/aer_inject should be created. - -Then, you need a user space tool named aer-inject, which can be gotten -from: - https://git.kernel.org/cgit/linux/kernel/git/gong.chen/aer-inject.git/ - -More information about aer-inject can be found in the document comes -with its source code. |