From 12e671142daa5d4dce5961e6f573a8b740b16f88 Mon Sep 17 00:00:00 2001 From: Simon Glass Date: Tue, 14 Apr 2015 21:03:21 -0600 Subject: fdt: Add binding decode function for display-timings This is useful for display parameters. Add a simple decode function to read from this device tree node. Signed-off-by: Simon Glass Signed-off-by: Tom Warren --- doc/device-tree-bindings/video/display-timing.txt | 110 ++++++++++++++++++++++ 1 file changed, 110 insertions(+) create mode 100644 doc/device-tree-bindings/video/display-timing.txt (limited to 'doc/device-tree-bindings/video/display-timing.txt') diff --git a/doc/device-tree-bindings/video/display-timing.txt b/doc/device-tree-bindings/video/display-timing.txt new file mode 100644 index 0000000000..e1d4a0b596 --- /dev/null +++ b/doc/device-tree-bindings/video/display-timing.txt @@ -0,0 +1,110 @@ +display-timing bindings +======================= + +display-timings node +-------------------- + +required properties: + - none + +optional properties: + - native-mode: The native mode for the display, in case multiple modes are + provided. When omitted, assume the first node is the native. + +timing subnode +-------------- + +required properties: + - hactive, vactive: display resolution + - hfront-porch, hback-porch, hsync-len: horizontal display timing parameters + in pixels + vfront-porch, vback-porch, vsync-len: vertical display timing parameters in + lines + - clock-frequency: display clock in Hz + +optional properties: + - hsync-active: hsync pulse is active low/high/ignored + - vsync-active: vsync pulse is active low/high/ignored + - de-active: data-enable pulse is active low/high/ignored + - pixelclk-active: with + - active high = drive pixel data on rising edge/ + sample data on falling edge + - active low = drive pixel data on falling edge/ + sample data on rising edge + - ignored = ignored + - interlaced (bool): boolean to enable interlaced mode + - doublescan (bool): boolean to enable doublescan mode + - doubleclk (bool): boolean to enable doubleclock mode + +All the optional properties that are not bool follow the following logic: + <1>: high active + <0>: low active + omitted: not used on hardware + +There are different ways of describing the capabilities of a display. The +devicetree representation corresponds to the one commonly found in datasheets +for displays. If a display supports multiple signal timings, the native-mode +can be specified. + +The parameters are defined as: + + +----------+-------------------------------------+----------+-------+ + | | ↑ | | | + | | |vback_porch | | | + | | ↓ | | | + +----------#######################################----------+-------+ + | # ↑ # | | + | # | # | | + | hback # | # hfront | hsync | + | porch # | hactive # porch | len | + |<-------->#<-------+--------------------------->#<-------->|<----->| + | # | # | | + | # |vactive # | | + | # | # | | + | # ↓ # | | + +----------#######################################----------+-------+ + | | ↑ | | | + | | |vfront_porch | | | + | | ↓ | | | + +----------+-------------------------------------+----------+-------+ + | | ↑ | | | + | | |vsync_len | | | + | | ↓ | | | + +----------+-------------------------------------+----------+-------+ + +Example: + + display-timings { + native-mode = <&timing0>; + timing0: 1080p24 { + /* 1920x1080p24 */ + clock-frequency = <52000000>; + hactive = <1920>; + vactive = <1080>; + hfront-porch = <25>; + hback-porch = <25>; + hsync-len = <25>; + vback-porch = <2>; + vfront-porch = <2>; + vsync-len = <2>; + hsync-active = <1>; + }; + }; + +Every required property also supports the use of ranges, so the commonly used +datasheet description with minimum, typical and maximum values can be used. + +Example: + + timing1: timing { + /* 1920x1080p24 */ + clock-frequency = <148500000>; + hactive = <1920>; + vactive = <1080>; + hsync-len = <0 44 60>; + hfront-porch = <80 88 95>; + hback-porch = <100 148 160>; + vfront-porch = <0 4 6>; + vback-porch = <0 36 50>; + vsync-len = <0 5 6>; + }; -- cgit