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https://github.com/brain-hackers/u-boot-brain
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12e671142d
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>
111 lines
4.0 KiB
Plaintext
111 lines
4.0 KiB
Plaintext
display-timing bindings
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=======================
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display-timings node
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--------------------
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required properties:
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- none
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optional properties:
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- native-mode: The native mode for the display, in case multiple modes are
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provided. When omitted, assume the first node is the native.
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timing subnode
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--------------
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required properties:
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- hactive, vactive: display resolution
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- hfront-porch, hback-porch, hsync-len: horizontal display timing parameters
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in pixels
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vfront-porch, vback-porch, vsync-len: vertical display timing parameters in
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lines
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- clock-frequency: display clock in Hz
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optional properties:
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- hsync-active: hsync pulse is active low/high/ignored
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- vsync-active: vsync pulse is active low/high/ignored
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- de-active: data-enable pulse is active low/high/ignored
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- pixelclk-active: with
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- active high = drive pixel data on rising edge/
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sample data on falling edge
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- active low = drive pixel data on falling edge/
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sample data on rising edge
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- ignored = ignored
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- interlaced (bool): boolean to enable interlaced mode
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- doublescan (bool): boolean to enable doublescan mode
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- doubleclk (bool): boolean to enable doubleclock mode
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All the optional properties that are not bool follow the following logic:
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<1>: high active
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<0>: low active
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omitted: not used on hardware
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There are different ways of describing the capabilities of a display. The
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devicetree representation corresponds to the one commonly found in datasheets
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for displays. If a display supports multiple signal timings, the native-mode
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can be specified.
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The parameters are defined as:
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+----------+-------------------------------------+----------+-------+
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| | ↑ | | |
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| | |vback_porch | | |
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| | ↓ | | |
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+----------#######################################----------+-------+
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| # ↑ # | |
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| # | # | |
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| hback # | # hfront | hsync |
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| porch # | hactive # porch | len |
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|<-------->#<-------+--------------------------->#<-------->|<----->|
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| # | # | |
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| # |vactive # | |
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| # | # | |
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| # ↓ # | |
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+----------#######################################----------+-------+
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| | ↑ | | |
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| | |vfront_porch | | |
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| | ↓ | | |
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+----------+-------------------------------------+----------+-------+
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| | ↑ | | |
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| | |vsync_len | | |
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| | ↓ | | |
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+----------+-------------------------------------+----------+-------+
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Example:
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display-timings {
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native-mode = <&timing0>;
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timing0: 1080p24 {
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/* 1920x1080p24 */
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clock-frequency = <52000000>;
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hactive = <1920>;
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vactive = <1080>;
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hfront-porch = <25>;
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hback-porch = <25>;
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hsync-len = <25>;
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vback-porch = <2>;
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vfront-porch = <2>;
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vsync-len = <2>;
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hsync-active = <1>;
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};
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};
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Every required property also supports the use of ranges, so the commonly used
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datasheet description with minimum, typical and maximum values can be used.
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Example:
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timing1: timing {
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/* 1920x1080p24 */
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clock-frequency = <148500000>;
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hactive = <1920>;
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vactive = <1080>;
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hsync-len = <0 44 60>;
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hfront-porch = <80 88 95>;
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hback-porch = <100 148 160>;
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vfront-porch = <0 4 6>;
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vback-porch = <0 36 50>;
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vsync-len = <0 5 6>;
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};
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