dt-bindings: sound: lpass-cpu: Document DAI subnodes

The lpass-cpu driver now allows configuring the MI2S SD lines
by defining subnodes for one of the DAIs.

Document this in the device tree bindings.

Signed-off-by: Stephan Gerhold <stephan@gerhold.net>
Link: https://lore.kernel.org/r/20200425184657.121991-1-stephan@gerhold.net
Signed-off-by: Mark Brown <broonie@kernel.org>

diff --git a/Documentation/devicetree/bindings/sound/qcom,lpass-cpu.txt b/Documentation/devicetree/bindings/sound/qcom,lpass-cpu.txt
index 21c6483..32c2cdb 100644 (file)
--- a/Documentation/devicetree/bindings/sound/qcom,lpass-cpu.txt
+++ b/Documentation/devicetree/bindings/sound/qcom,lpass-cpu.txt
@@ -30,6 +30,8 @@ Required properties:
 - reg                  : Must contain an address for each entry in reg-names.
 - reg-names            : A list which must include the following entries:
                                * "lpass-lpaif"
+- #address-cells       : Must be 1
+- #size-cells          : Must be 0
 
 
 
@@ -37,6 +39,20 @@ Optional properties:
 
 - qcom,adsp            : Phandle for the audio DSP node
 
+By default, the driver uses up to 4 MI2S SD lines, for a total of 8 channels.
+The SD lines to use can be configured by adding subnodes for each of the DAIs.
+
+Required properties for each DAI (represented by a subnode):
+- reg                  : Must be one of the DAI IDs
+                         (usually part of dt-bindings header)
+- qcom,playback-sd-lines: List of serial data lines to use for playback
+                         Each SD line should be represented by a number from 0-3.
+- qcom,capture-sd-lines        : List of serial data lines to use for capture
+                         Each SD line should be represented by a number from 0-3.
+
+Note that adding a subnode changes the default to "no lines configured",
+so both playback and capture lines should be configured when a subnode is added.
+
 Example:
 
 lpass@28100000 {
@@ -51,4 +67,13 @@ lpass@28100000 {
        reg = <0x28100000 0x10000>;
        reg-names = "lpass-lpaif";
        qcom,adsp = <&adsp>;
+
+       #address-cells = <1>;
+       #size-cells = <0>;
+
+       /* Optional to set different MI2S SD lines */
+       dai@3 {
+               reg = <MI2S_QUATERNARY>;
+               qcom,playback-sd-lines = <0 1>;
+       };
 };