diff options
Diffstat (limited to 'Documentation/devicetree')
| -rw-r--r-- | Documentation/devicetree/bindings/chosen.txt | 46 | ||||
| -rw-r--r-- | Documentation/devicetree/bindings/serial/pl011.txt | 28 | ||||
| -rw-r--r-- | Documentation/devicetree/bindings/unittest.txt | 14 | ||||
| -rw-r--r-- | Documentation/devicetree/of_selftest.txt | 20 | ||||
| -rw-r--r-- | Documentation/devicetree/overlay-notes.txt | 133 | ||||
| -rw-r--r-- | Documentation/devicetree/todo.txt | 1 |
6 files changed, 221 insertions, 21 deletions
diff --git a/Documentation/devicetree/bindings/chosen.txt b/Documentation/devicetree/bindings/chosen.txt new file mode 100644 index 000000000000..ed838f453f7a --- /dev/null +++ b/Documentation/devicetree/bindings/chosen.txt @@ -0,0 +1,46 @@ +The chosen node +--------------- + +The chosen node does not represent a real device, but serves as a place +for passing data between firmware and the operating system, like boot +arguments. Data in the chosen node does not represent the hardware. + + +stdout-path property +-------------------- + +Device trees may specify the device to be used for boot console output +with a stdout-path property under /chosen, as described in ePAPR, e.g. + +/ { + chosen { + stdout-path = "/serial@f00:115200"; + }; + + serial@f00 { + compatible = "vendor,some-uart"; + reg = <0xf00 0x10>; + }; +}; + +If the character ":" is present in the value, this terminates the path. +The meaning of any characters following the ":" is device-specific, and +must be specified in the relevant binding documentation. + +For UART devices, the preferred binding is a string in the form: + + <baud>{<parity>{<bits>{<flow>}}} + +where + + baud - baud rate in decimal + parity - 'n' (none), 'o', (odd) or 'e' (even) + bits - number of data bits + flow - 'r' (rts) + +For example: 115200n8r + +Implementation note: Linux will look for the property "linux,stdout-path" or +on PowerPC "stdout" if "stdout-path" is not found. However, the +"linux,stdout-path" and "stdout" properties are deprecated. New platforms +should only use the "stdout-path" property. diff --git a/Documentation/devicetree/bindings/serial/pl011.txt b/Documentation/devicetree/bindings/serial/pl011.txt index 5d2e840ae65c..52464918cfe2 100644 --- a/Documentation/devicetree/bindings/serial/pl011.txt +++ b/Documentation/devicetree/bindings/serial/pl011.txt @@ -6,12 +6,34 @@ Required properties: - interrupts: exactly one interrupt specifier Optional properties: -- pinctrl: When present, must have one state named "sleep" - and one state named "default" -- clocks: When present, must refer to exactly one clock named +- pinctrl: When present, must have one state named "default", + and may contain a second name named "sleep". The former + state sets up pins for ordinary operation whereas + the latter state will put the associated pins to sleep + when the UART is unused +- clocks: When present, the first clock listed must correspond to + the clock named UARTCLK on the IP block, i.e. the clock + to the external serial line, whereas the second clock + must correspond to the PCLK clocking the internal logic + of the block. Just listing one clock (the first one) is + deprecated. +- clocks-names: When present, the first clock listed must be named + "uartclk" and the second clock listed must be named "apb_pclk" - dmas: When present, may have one or two dma channels. The first one must be named "rx", the second one must be named "tx". See also bindings/arm/primecell.txt + +Example: + +uart@80120000 { + compatible = "arm,pl011", "arm,primecell"; + reg = <0x80120000 0x1000>; + interrupts = <0 11 IRQ_TYPE_LEVEL_HIGH>; + dmas = <&dma 13 0 0x2>, <&dma 13 0 0x0>; + dma-names = "rx", "tx"; + clocks = <&foo_clk>, <&bar_clk>; + clock-names = "uartclk", "apb_pclk"; +}; diff --git a/Documentation/devicetree/bindings/unittest.txt b/Documentation/devicetree/bindings/unittest.txt new file mode 100644 index 000000000000..0f92a22fddfa --- /dev/null +++ b/Documentation/devicetree/bindings/unittest.txt @@ -0,0 +1,14 @@ +* OF selftest platform device + +** selftest + +Required properties: +- compatible: must be "selftest" + +All other properties are optional. + +Example: + selftest { + compatible = "selftest"; + status = "okay"; + }; diff --git a/Documentation/devicetree/of_selftest.txt b/Documentation/devicetree/of_selftest.txt index 1e3d5c92b5e3..57a808b588bf 100644 --- a/Documentation/devicetree/of_selftest.txt +++ b/Documentation/devicetree/of_selftest.txt @@ -63,7 +63,6 @@ struct device_node { struct device_node *parent; struct device_node *child; struct device_node *sibling; - struct device_node *allnext; /* next in list of all nodes */ ... }; @@ -99,12 +98,6 @@ child11 -> sibling12 -> sibling13 -> sibling14 -> null Figure 1: Generic structure of un-flattened device tree -*allnext: it is used to link all the nodes of DT into a list. So, for the - above tree the list would be as follows: - -root->child1->child11->sibling12->sibling13->child131->sibling14->sibling2-> -child21->sibling22->sibling23->sibling3->child31->sibling32->sibling4->null - Before executing OF selftest, it is required to attach the test data to machine's device tree (if present). So, when selftest_data_add() is called, at first it reads the flattened device tree data linked into the kernel image @@ -131,11 +124,6 @@ root ('/') test-child01 null null null -allnext list: - -root->testcase-data->test-child0->test-child01->test-sibling1->test-sibling2 -->test-sibling3->null - Figure 2: Example test data tree to be attached to live tree. According to the scenario above, the live tree is already present so it isn't @@ -204,8 +192,6 @@ detached and then moving up the parent nodes are removed, and eventually the whole tree). selftest_data_remove() calls detach_node_and_children() that uses of_detach_node() to detach the nodes from the live device tree. -To detach a node, of_detach_node() first updates all_next linked list, by -attaching the previous node's allnext to current node's allnext pointer. And -then, it either updates the child pointer of given node's parent to its -sibling or attaches the previous sibling to the given node's sibling, as -appropriate. That is it :) +To detach a node, of_detach_node() either updates the child pointer of given +node's parent to its sibling or attaches the previous sibling to the given +node's sibling, as appropriate. That is it :) diff --git a/Documentation/devicetree/overlay-notes.txt b/Documentation/devicetree/overlay-notes.txt new file mode 100644 index 000000000000..30ae758e3eef --- /dev/null +++ b/Documentation/devicetree/overlay-notes.txt @@ -0,0 +1,133 @@ +Device Tree Overlay Notes +------------------------- + +This document describes the implementation of the in-kernel +device tree overlay functionality residing in drivers/of/overlay.c and is a +companion document to Documentation/devicetree/dt-object-internal.txt[1] & +Documentation/devicetree/dynamic-resolution-notes.txt[2] + +How overlays work +----------------- + +A Device Tree's overlay purpose is to modify the kernel's live tree, and +have the modification affecting the state of the the kernel in a way that +is reflecting the changes. +Since the kernel mainly deals with devices, any new device node that result +in an active device should have it created while if the device node is either +disabled or removed all together, the affected device should be deregistered. + +Lets take an example where we have a foo board with the following base tree +which is taken from [1]. + +---- foo.dts ----------------------------------------------------------------- + /* FOO platform */ + / { + compatible = "corp,foo"; + + /* shared resources */ + res: res { + }; + + /* On chip peripherals */ + ocp: ocp { + /* peripherals that are always instantiated */ + peripheral1 { ... }; + } + }; +---- foo.dts ----------------------------------------------------------------- + +The overlay bar.dts, when loaded (and resolved as described in [2]) should + +---- bar.dts ----------------------------------------------------------------- +/plugin/; /* allow undefined label references and record them */ +/ { + .... /* various properties for loader use; i.e. part id etc. */ + fragment@0 { + target = <&ocp>; + __overlay__ { + /* bar peripheral */ + bar { + compatible = "corp,bar"; + ... /* various properties and child nodes */ + } + }; + }; +}; +---- bar.dts ----------------------------------------------------------------- + +result in foo+bar.dts + +---- foo+bar.dts ------------------------------------------------------------- + /* FOO platform + bar peripheral */ + / { + compatible = "corp,foo"; + + /* shared resources */ + res: res { + }; + + /* On chip peripherals */ + ocp: ocp { + /* peripherals that are always instantiated */ + peripheral1 { ... }; + + /* bar peripheral */ + bar { + compatible = "corp,bar"; + ... /* various properties and child nodes */ + } + } + }; +---- foo+bar.dts ------------------------------------------------------------- + +As a result of the the overlay, a new device node (bar) has been created +so a bar platform device will be registered and if a matching device driver +is loaded the device will be created as expected. + +Overlay in-kernel API +-------------------------------- + +The API is quite easy to use. + +1. Call of_overlay_create() to create and apply an overlay. The return value +is a cookie identifying this overlay. + +2. Call of_overlay_destroy() to remove and cleanup the overlay previously +created via the call to of_overlay_create(). Removal of an overlay that +is stacked by another will not be permitted. + +Finally, if you need to remove all overlays in one-go, just call +of_overlay_destroy_all() which will remove every single one in the correct +order. + +Overlay DTS Format +------------------ + +The DTS of an overlay should have the following format: + +{ + /* ignored properties by the overlay */ + + fragment@0 { /* first child node */ + + target=<phandle>; /* phandle target of the overlay */ + or + target-path="/path"; /* target path of the overlay */ + + __overlay__ { + property-a; /* add property-a to the target */ + node-a { /* add to an existing, or create a node-a */ + ... + }; + }; + } + fragment@1 { /* second child node */ + ... + }; + /* more fragments follow */ +} + +Using the non-phandle based target method allows one to use a base DT which does +not contain a __symbols__ node, i.e. it was not compiled with the -@ option. +The __symbols__ node is only required for the target=<phandle> method, since it +contains the information required to map from a phandle to a tree location. diff --git a/Documentation/devicetree/todo.txt b/Documentation/devicetree/todo.txt index c3cf0659bd19..b5139d1de811 100644 --- a/Documentation/devicetree/todo.txt +++ b/Documentation/devicetree/todo.txt @@ -2,7 +2,6 @@ Todo list for devicetree: === General structure === - Switch from custom lists to (h)list_head for nodes and properties structure -- Remove of_allnodes list and iterate using list of child nodes alone === CONFIG_OF_DYNAMIC === - Switch to RCU for tree updates and get rid of global spinlock |