Re: [PATCH v3 12/14] dt-bindings: msm/dp: Add bindings for HDCP registers

[Bjorn Andersson <bjorn.andersson@linaro.org>]

On Fri 01 Oct 10:11 CDT 2021, Sean Paul wrote:

> From: Sean Paul <seanpaul@chromium.org>
> 
> This patch adds the bindings for the MSM DisplayPort HDCP registers
> which are required to write the HDCP key into the display controller as
> well as the registers to enable HDCP authentication/key
> exchange/encryption.
> 
> We'll use a new compatible string for this since the fields are optional.
> 

I don't think you need a new compatible, in particular since I presume
we should use the hdcp compatible in all platforms? Or is there a reason
for not picking that one?

Instead I suggest that you simply do minItems: 1, maxItems: 3 and detect
which of the two cases you have in the driver.

PS. I hope to get
https://lore.kernel.org/linux-arm-msm/20211001174400.981707-1-bjorn.andersson@linaro.org/
landed before we add these new optional regions...

Regards,
Bjorn

> Cc: Rob Herring <robh@kernel.org>
> Cc: Stephen Boyd <swboyd@chromium.org>
> Signed-off-by: Sean Paul <seanpaul@chromium.org>
> Link: https://patchwork.freedesktop.org/patch/msgid/20210913175747.47456-13-sean@poorly.run #v1
> Link: https://patchwork.freedesktop.org/patch/msgid/20210915203834.1439-13-sean@poorly.run #v2
> 
> Changes in v2:
> -Drop register range names (Stephen)
> -Fix yaml errors (Rob)
> Changes in v3:
> -Add new compatible string for dp-hdcp
> -Add descriptions to reg
> -Add minItems/maxItems to reg
> -Make reg depend on the new hdcp compatible string
> ---
> 
> Disclaimer: I really don't know if this is the right way to approach
> this. I tried using examples from other bindings, but feedback would be
> very much welcome on how I could add the optional register ranges.
> 
> 
>  .../bindings/display/msm/dp-controller.yaml   | 34 ++++++++++++++++---
>  1 file changed, 30 insertions(+), 4 deletions(-)
> 
> diff --git a/Documentation/devicetree/bindings/display/msm/dp-controller.yaml b/Documentation/devicetree/bindings/display/msm/dp-controller.yaml
> index 64d8d9e5e47a..a176f97b2f4c 100644
> --- a/Documentation/devicetree/bindings/display/msm/dp-controller.yaml
> +++ b/Documentation/devicetree/bindings/display/msm/dp-controller.yaml
> @@ -17,9 +17,10 @@ properties:
>    compatible:
>      enum:
>        - qcom,sc7180-dp
> +      - qcom,sc7180-dp-hdcp
>  
> -  reg:
> -    maxItems: 1
> +  # See compatible-specific constraints below.
> +  reg: true
>  
>    interrupts:
>      maxItems: 1
> @@ -89,6 +90,29 @@ required:
>    - power-domains
>    - ports
>  
> +allOf:
> +  - if:
> +      properties:
> +        compatible:
> +          contains:
> +            const: qcom,sc7180-dp-hdcp
> +    then:
> +      properties:
> +        reg:
> +          minItems: 3
> +          maxItems: 3
> +          items:
> +            - description: Registers for base DP functionality
> +            - description: (Optional) Registers for HDCP device key injection
> +            - description: (Optional) Registers for HDCP TrustZone interaction
> +    else:
> +      properties:
> +        reg:
> +          minItems: 1
> +          maxItems: 1
> +          items:
> +            - description: Registers for base DP functionality
> +
>  additionalProperties: false
>  
>  examples:
> @@ -99,8 +123,10 @@ examples:
>      #include <dt-bindings/power/qcom-rpmpd.h>
>  
>      displayport-controller@ae90000 {
> -        compatible = "qcom,sc7180-dp";
> -        reg = <0xae90000 0x1400>;
> +        compatible = "qcom,sc7180-dp-hdcp";
> +        reg = <0 0x0ae90000 0 0x1400>,
> +              <0 0x0aed1000 0 0x174>,
> +              <0 0x0aee1000 0 0x2c>;
>          interrupt-parent = <&mdss>;
>          interrupts = <12>;
>          clocks = <&dispcc DISP_CC_MDSS_AHB_CLK>,
> -- 
> Sean Paul, Software Engineer, Google / Chromium OS
>