Re: [PATCH 1/3] dt-bindings: display: msm: Add binding for MSM8996 DPU

[Dmitry Baryshkov]

On 30/04/2022 22:33, Dmitry Baryshkov wrote:
> On 30/04/2022 19:15, Konrad Dybcio wrote:
> > Add yaml binding for MSM8996 DPU.
> >
> > Signed-off-by: Konrad Dybcio <konrad.dybcio@xxxxxxxxxxxxxx>
> > ---
> >   .../bindings/display/msm/dpu-msm8996.yaml     | 221 ++++++++++++++++++
> >   1 file changed, 221 insertions(+)
> >   create mode 100644 
> > Documentation/devicetree/bindings/display/msm/dpu-msm8996.yaml
> >
> > diff --git 
> > a/Documentation/devicetree/bindings/display/msm/dpu-msm8996.yaml 
> > b/Documentation/devicetree/bindings/display/msm/dpu-msm8996.yaml
> > new file mode 100644
> > index 000000000000..10b02423224d
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/display/msm/dpu-msm8996.yaml
> > @@ -0,0 +1,221 @@
> > +# SPDX-License-Identifier: GPL-2.0-only or BSD-2-Clause
> > +%YAML 1.2
> > +---
> > +$id: http://devicetree.org/schemas/display/msm/dpu-msm8996.yaml#
> > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > +
> > +title: Qualcomm Display DPU dt properties for MSM8996 target
> > +
> > +maintainers:
> > +  - Konrad Dybcio <konrad.dybcio@xxxxxxxxxxxxxx>
> > +
> > +description: |
> > +  Device tree bindings for MSM Mobile Display Subsystem (MDSS) that
> > +  encapsulates sub-blocks like DPU display controller, DSI 
> > interfaces, etc.
> > +  Device tree bindings of MDSS and DPU are mentioned for MSM8996 target.
> > +
> > +properties:
> > +  compatible:
> > +    items:
> > +      - const: qcom,msm8996-mdss
>
> With the unified MDSS driver there is no need to describe a separate 
> mdss bindings. Let's skip this part for now.
>
> > +
> > +  reg:
> > +    maxItems: 1
> > +
> > +  reg-names:
> > +    const: mdss
> > +
> > +  power-domains:
> > +    maxItems: 1
> > +
> > +  clocks:
> > +    items:
> > +      - description: Display AHB clock
> > +      - description: Display core clock
> > +
> > +  clock-names:
> > +    items:
> > +      - const: iface
> > +      - const: core
> > +
> > +  interrupts:
> > +    maxItems: 1
> > +
> > +  interrupt-controller: true
> > +
> > +  "#address-cells": true
> > +
> > +  "#size-cells": true
> > +
> > +  "#interrupt-cells":
> > +    const: 1
> > +
> > +  iommus:
> > +    items:
> > +      - description: Phandle to mdp_smmu node with SID mask for 
> > Hard-Fail port0
> > +
> > +  ranges: true
> > +
> > +patternProperties:
> > +  "^display-controller@[0-9a-f]+$":
> > +    type: object
> > +    description: Node containing the properties of DPU.
> > +
> > +    properties:
> > +      compatible:
> > +        items:
> > +          - const: qcom,msm8996-dpu
>
> Okay. So, this is the most interesting part. Unlike MSM8998, which is 
> supported in the mdp5 driver, but was not used in the upstream DTS 
> files, for the MSM8996 the MDP5 part is described, used and widely 
> tested. And, unfortunately, the bindings use solely the generic 
> "qcom,mdp5" compat.
>
> I would suggest the following plan:
> - Define a binding using both "qcom,msm8996-dpu" and "qcom,mdp5" 
> strings. Make sure that it is fully backwards-compatible with older dts.
>
> - Update msm8996.dtsi to follow new binding.
>
> - Let's have a Kconfig flip switch selecting which driver to be used for 
> 8996/8998.

Rob suggested a modparam here.


--
With best wishes
Dmitry