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authorSimon Glass <sjg@chromium.org>2015-04-14 21:03:21 -0600
committerTom Warren <twarren@nvidia.com>2015-05-13 09:24:06 -0700
commit12e671142daa5d4dce5961e6f573a8b740b16f88 (patch)
tree30eafbb47ee45d9de1683074067fd573163a0c20 /doc/device-tree-bindings
parent962f5caf600c54f4103bfa6b31fa2fb4e8aaacb9 (diff)
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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 <sjg@chromium.org> Signed-off-by: Tom Warren <twarren@nvidia.com>
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diff --git a/doc/device-tree-bindings/video/display-timing.txt b/doc/device-tree-bindings/video/display-timing.txt
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+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>;
+ };