Add binding document for the Pulse Density Modulator (PDM) DAC present on the
Pistachio SOC.
Signed-off-by: Naidu Tellapati <Naidu.Tellapati@xxxxxxxxxx>
Signed-off-by: Arul Ramasamy <Arul.Ramasamy@xxxxxxxxxx>
---
Documentation/devicetree/bindings/misc/img-pdm.txt | 54 ++++++++++++++++++++
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+*Imagination Technologies Pulse Density Modulator (PDM) DAC.
+
+Required properties:
+ - compatible: Must be "img,pistachio-pdm"
+ - clocks: Must contain an entry for each entry in clock-names.
+ - clock-names: Must include the following entry:
+ Required elements: "pdm"
+ - img,cr-periph: Must contain a phandle to the peripheral control
+ syscon node which contains PDM control registers.
+ - #pdm-cells: Must be 2.
+ - The first cell is the PDM channel number (valid values: 0, 1, 2, 3)
+ - The second cell is 12-bit pulse-in value
+
+Specifying PDM information for devices
+======================================
+
+1. PDM User nodes
+
+PDM properties should be named "pdms". The exact meaning of each pdms property
+is described above.
+
+ pdm-specifier : array of #pdm-cells specifying the given PDM
+ (controller specific)
+
+The following example could be used to describe a PDM-based backlight device:
+
+ pdm: pdm {
+ #pdm-cells = <2>;
+ };
+
+ [...]
+
+ bl: backlight {
+ pdms = <&pdm 2 0>;
+ };
+
+pdm-specifier typically encodes the chip-relative PDM channel number and the
+12-bit pulse-in value.
+
+2. PDM Controller nodes
+
+PDM controller nodes must specify the number of cells used for the specifier
+using the '#pdm-cells' property.
+
+An example PDM controller might look like this:
+
+Example:
+ pdm: pdm@18148000 {
+ compatible = "img,pistachio-pdm";
+ clocks = <&pdm_clk>;
+ clk-names = "pdm";
+ img,cr-periph = <&cr_periph>;
+ #pdm-cells = <2>;
+ };
--
1.7.0.4
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