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authorLinus Torvalds <torvalds@linux-foundation.org>2015-11-06 21:17:09 +0100
committerLinus Torvalds <torvalds@linux-foundation.org>2015-11-06 21:17:09 +0100
commit9bbd4b9f38f56b4ee2c8ff268a1104ff38333e90 (patch)
tree7e889c87c06165e553fdc9056b9fa4d91b91a5ee /Documentation/devicetree/bindings/display/simple-framebuffer.txt
parentMerge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/dto... (diff)
parentMAINTAINERS: update DT binding doc locations (diff)
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Merge tag 'devicetree-for-4.4' of git://git.kernel.org/pub/scm/linux/kernel/git/robh/linux
Pull DeviceTree updates from Rob Herring: "A fairly large (by DT standards) pull request this time with the majority being some overdue moving DT binding docs around to consolidate similar bindings. - DT binding doc consolidation moving similar bindings to common locations. The majority of these are display related which were scattered in video/, fb/, drm/, gpu/, and panel/ directories. - Add new config option, CONFIG_OF_ALL_DTBS, to enable building all dtbs in the tree for most arches with dts files (except powerpc for now). - OF_IRQ=n fixes for user enabled CONFIG_OF. - of_node_put ref counting fixes from Julia Lawall. - Common DT binding for wakeup-source and deprecation of all similar bindings. - DT binding for PXA LCD controller. - Allow ignoring failed PCI resource translations in order to ignore 64-bit addresses on non-LPAE 32-bit kernels. - Support setting the NUMA node from DT instead of only from parent device. - Couple of earlycon DT parsing fixes for address and options" * tag 'devicetree-for-4.4' of git://git.kernel.org/pub/scm/linux/kernel/git/robh/linux: (45 commits) MAINTAINERS: update DT binding doc locations devicetree: add Sigma Designs vendor prefix of: simplify arch_find_n_match_cpu_physical_id() function Documentation: arm: Fixed typo in socfpga fpga mgr example Documentation: devicetree: fix reference to legacy wakeup properties Documentation: devicetree: standardize/consolidate on "wakeup-source" property drivers: of: removing assignment of 0 to static variable xtensa: enable building of all dtbs mips: enable building of all dtbs metag: enable building of all dtbs metag: use common make variables for dtb builds h8300: enable building of all dtbs arm64: enable building of all dtbs arm: enable building of all dtbs arc: enable building of all dtbs arc: use common make variables for dtb builds of: add config option to enable building of all dtbs of/fdt: fix error checking for earlycon address of/overlay: add missing of_node_put of/platform: add missing of_node_put ...
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+Simple Framebuffer
+
+A simple frame-buffer describes a frame-buffer setup by firmware or
+the bootloader, with the assumption that the display hardware has already
+been set up to scan out from the memory pointed to by the reg property.
+
+Since simplefb nodes represent runtime information they must be sub-nodes of
+the chosen node (*). Simplefb nodes must be named "framebuffer@<address>".
+
+If the devicetree contains nodes for the display hardware used by a simplefb,
+then the simplefb node must contain a property called "display", which
+contains a phandle pointing to the primary display hw node, so that the OS
+knows which simplefb to disable when handing over control to a driver for the
+real hardware. The bindings for the hw nodes must specify which node is
+considered the primary node.
+
+It is advised to add display# aliases to help the OS determine how to number
+things. If display# aliases are used, then if the simplefb node contains a
+"display" property then the /aliases/display# path must point to the display
+hw node the "display" property points to, otherwise it must point directly
+to the simplefb node.
+
+If a simplefb node represents the preferred console for user interaction,
+then the chosen node's stdout-path property should point to it, or to the
+primary display hw node, as with display# aliases. If display aliases are
+used then it should be set to the alias instead.
+
+It is advised that devicetree files contain pre-filled, disabled framebuffer
+nodes, so that the firmware only needs to update the mode information and
+enable them. This way if e.g. later on support for more display clocks get
+added, the simplefb nodes will already contain this info and the firmware
+does not need to be updated.
+
+If pre-filled framebuffer nodes are used, the firmware may need extra
+information to find the right node. In that case an extra platform specific
+compatible and platform specific properties should be used and documented,
+see e.g. simple-framebuffer-sunxi.txt .
+
+Required properties:
+- compatible: "simple-framebuffer"
+- reg: Should contain the location and size of the framebuffer memory.
+- width: The width of the framebuffer in pixels.
+- height: The height of the framebuffer in pixels.
+- stride: The number of bytes in each line of the framebuffer.
+- format: The format of the framebuffer surface. Valid values are:
+ - r5g6b5 (16-bit pixels, d[15:11]=r, d[10:5]=g, d[4:0]=b).
+ - a8b8g8r8 (32-bit pixels, d[31:24]=a, d[23:16]=b, d[15:8]=g, d[7:0]=r).
+
+Optional properties:
+- clocks : List of clocks used by the framebuffer. Clocks listed here
+ are expected to already be configured correctly. The OS must
+ ensure these clocks are not modified or disabled while the
+ simple framebuffer remains active.
+- display : phandle pointing to the primary display hardware node
+
+Example:
+
+aliases {
+ display0 = &lcdc0;
+}
+
+chosen {
+ framebuffer0: framebuffer@1d385000 {
+ compatible = "simple-framebuffer";
+ reg = <0x1d385000 (1600 * 1200 * 2)>;
+ width = <1600>;
+ height = <1200>;
+ stride = <(1600 * 2)>;
+ format = "r5g6b5";
+ clocks = <&ahb_gates 36>, <&ahb_gates 43>, <&ahb_gates 44>;
+ display = <&lcdc0>;
+ };
+ stdout-path = "display0";
+};
+
+soc@01c00000 {
+ lcdc0: lcdc@1c0c000 {
+ compatible = "allwinner,sun4i-a10-lcdc";
+ ...
+ };
+};
+
+
+*) Older devicetree files may have a compatible = "simple-framebuffer" node
+in a different place, operating systems must first enumerate any compatible
+nodes found under chosen and then check for other compatible nodes.