[PATCH v6 15/16] dt-bindings: display: rockchip: dw-dp: Fix sound DAI cells

[Sebastian Reichel]

The RK3588 and RK3576 DesignWare DisplayPort controllers both have two
possible DAI interfaces: I2S and S/PDIF. Thus an argument is needed to
to select the right interface.

In addition to that the RK3576 DisplayPort controller is configured
with Multi Stream Transport (MST) enabled for up to 3 displays and
thus has a total of 6 DAI interfaces (I2S and S/PDIF for each possible
stream). Meanwhile the RK3588 does not support MST and thus has only 2
DAI interfaces.

The binding update from this patch has only been tested with the simple
single stream transport (SST) setup as the Linux driver does not yet
support MST. Once MST support is added, the plan is to simply add more
numbers to the argument, so that it looks like this for RK3576:

0 = I2S on stream 0,
1 = S/PDIF on stream 0
2 = I2S on stream 1,
3 = S/PDIF on stream 1
4 = I2S on stream 2,
5 = S/PDIF on stream 2

As the arguments are not part of the binding itself the audio side
is also ready for MST after this change.

Switching '#sound-dai-cells' from 0 to 1 without keeping compatibility
is an ABI break. The rationale for going that way is, that there is not
a single known driver implementation for the current binding. It's also
unclear how the current binding would be used (only support I2S or
S/PDIF for stream 0?). The mainline rk3588 DTS include sets it to 0, but
does not have any soundcard using the DAI. This will be fixed up
separately. The RK3576 does not set it at all.

Signed-off-by: Sebastian Reichel <sebastian.reichel@xxxxxxxxxxxxx>
---
 .../devicetree/bindings/display/rockchip/rockchip,dw-dp.yaml     | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/Documentation/devicetree/bindings/display/rockchip/rockchip,dw-dp.yaml b/Documentation/devicetree/bindings/display/rockchip/rockchip,dw-dp.yaml
index 2b0d9e23e943..c4f8959dd65d 100644
--- a/Documentation/devicetree/bindings/display/rockchip/rockchip,dw-dp.yaml
+++ b/Documentation/devicetree/bindings/display/rockchip/rockchip,dw-dp.yaml
@@ -25,7 +25,7 @@ description: |
   * Supports up to 8/10 bits per color component
   * Supports RBG, YCbCr4:4:4, YCbCr4:2:2, YCbCr4:2:0
   * Pixel clock up to 594MHz
-  * I2S, SPDIF audio interface
+  * I2S, S/PDIF audio interface
 
 properties:
   compatible:
@@ -46,7 +46,7 @@ properties:
       - description: DisplayPort AUX clock
       - description: HDCP clock
       - description: I2S interface clock
-      - description: SPDIF interfce clock
+      - description: S/PDIF interfce clock
 
   clock-names:
     minItems: 3
@@ -83,7 +83,8 @@ properties:
     maxItems: 1
 
   "#sound-dai-cells":
-    const: 0
+    const: 1
+    description: 0 for I2S, 1 for S/PDIF
 
 required:
   - compatible
@@ -144,7 +145,7 @@ examples:
         resets = <&cru SRST_DP0>;
         phys = <&usbdp_phy0 PHY_TYPE_DP>;
         power-domains = <&power RK3588_PD_VO0>;
-        #sound-dai-cells = <0>;
+        #sound-dai-cells = <1>;
 
         ports {
           #address-cells = <1>;

-- 
2.53.0