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>

1 files changed, 110 insertions, 0 deletions

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 0000000..e1d4a0b
--- /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>;
+	};