Re: [PATCH v6 1/5] dt-bindings: msm/dp: add bindings of DP/DP-PLL driver for Snapdragon

[tanmay@codeaurora.org]

On 2020-06-09 19:15, Stephen Boyd wrote:
> Quoting Tanmay Shah (2020-06-08 20:38:18)
>> diff --git 
>> a/Documentation/devicetree/bindings/display/msm/dp-sc7180.yaml 
>> b/Documentation/devicetree/bindings/display/msm/dp-sc7180.yaml
>> new file mode 100644
>> index 0000000..5fdb915
>> --- /dev/null
>> +++ b/Documentation/devicetree/bindings/display/msm/dp-sc7180.yaml
> 
> Typically the file name matches the compatible string. But the
> compatible string is just qcom,dp-display. Maybe the compatible string
> should be qcom,sc7180-dp? Notice that the SoC number comes first as is
> preferred.
> 
These bindings will be similar for upcoming SOC as well.
So just for understanding, when we add new SOC do we create new file 
with same bidings
with SOC number in new file name?
Instead we can keep this file's name as qcom,dp-display.yaml (same as 
compatible const) and we can include SOC number in compatible enum ?
some examples:
https://patchwork.kernel.org/patch/11448357/
https://patchwork.kernel.org/patch/11164619/
> 
>> @@ -0,0 +1,142 @@
>> +# SPDX-License-Identifier: (GPL-2.0-only  OR BSD-2-Clause)
>> +%YAML 1.2
>> +---
>> +$id: http://devicetree.org/schemas/display/msm/dp-sc7180.yaml#
>> +$schema: http://devicetree.org/meta-schemas/core.yaml#
>> +
>> +title: Qualcomm Display Port Controller.
>> +
>> +maintainers:
>> +  - Chandan Uddaraju <chandanu@codeaurora.org>
>> +  - Vara Reddy <varar@codeaurora.org>
>> +  - Tanmay Shah <tanmay@codeaurora.org>
>> +
>> +description: |
>> +  Device tree bindings for MSM Display Port which supports DP host 
>> controllers
>> +  that are compatible with VESA Display Port interface specification.
>> +
>> +properties:
>> +  compatible:
>> +    items:
>> +      - const: qcom,dp-display
>> +
>> +  cell-index:
>> +    description: Specifies the controller instance.
>> +
>> +  reg:
>> +    items:
>> +      - description: DP controller registers
>> +
>> +  interrupts:
>> +    description: The interrupt signal from the DP block.
>> +
>> +  clocks:
>> +    description: List of clock specifiers for clocks needed by the 
>> device.
>> +    items:
>> +      - description: Display Port AUX clock
>> +      - description: Display Port Link clock
>> +      - description: Link interface clock between DP and PHY
>> +      - description: Display Port Pixel clock
>> +      - description: Root clock generator for pixel clock
>> +
>> +  clock-names:
>> +    description: |
>> +      Device clock names in the same order as mentioned in clocks 
>> property.
>> +      The required clocks are mentioned below.
>> +    items:
>> +      - const: core_aux
>> +      - const: ctrl_link
>> +      - const: ctrl_link_iface
>> +      - const: stream_pixel
>> +      - const: pixel_rcg
> 
> Why not just 'pixel'? And why is the root clk generator important? It
> looks like this binding should be using the assigned clock parents
> property instead so that it doesn't have to call clk_set_parent()
> explicitly.
> 
Are we talking about renaming stream_pixel to pixel only?
We divide clocks in categories: core, control and stream clock.
Similar terminology will be used in subsequent driver patches as well.

We can remove pixel_rcg use assigned clock parents property and remove 
clk_set_parent
from driver.

>> +  "#clock-cells":
>> +    const: 1
>> +
>> +  vdda-1p2-supply:
>> +    description: phandle to vdda 1.2V regulator node.
>> +
>> +  vdda-0p9-supply:
>> +    description: phandle to vdda 0.9V regulator node.
>> +
>> +  data-lanes = <0 1>:
> 
> Is this correct? We can have = <value> in the property name? Also feels
> generic and possibly should come from the phy binding instead of from
> the controller binding.
> 
We are using this property in DP controller programming sequence such as 
link training.
So I think we can keep this here.
You are right about <value>. <0 1> part should be in example only. It 
was passing through dt_binding_check though.
Here it should be like:
data-lanes:
minItems:1
maxItems:4

>> +    type: object
>> +    description: Maximum number of lanes that can be used for Display 
>> port.
>> +
>> +  ports:
>> +    description: |
>> +       Contains display port controller endpoint subnode.
>> +       remote-endpoint: |
>> +         For port@0, set to phandle of the connected panel/bridge's
>> +         input endpoint. For port@1, set to the DPU interface output.
>> +         Documentation/devicetree/bindings/graph.txt and
>> +         
>> Documentation/devicetree/bindings/media/video-interfaces.txt.
>> +
>> +patternProperties:
>> +  "^aux-cfg([0-9])-settings$":
>> +    type: object
>> +    description: |
>> +      Specifies the DP AUX configuration [0-9] settings.
>> +      The first entry in this array corresponds to the register 
>> offset
>> +      within DP AUX, while the remaining entries indicate the
>> +      programmable values.
> 
> I'd prefer this was removed from the binding and hardcoded in the 
> driver
> until we can understand what the values are. If they're not
> understandable then they most likely don't change and should be done in
> the driver.
> 
Typically customers tune these values by working with vendor. So for 
different boards it can be different. Even though it is hard for 
customers to do this themselves, these are still board specific and 
belong to dts. As requested earlier, we have added default values 
already and made these properties optional but, we would like to keep it 
in bindings so we can have option to tune them as required.
>> +
>> +required:
>> +  - compatible
>> +  - cell-index
>> +  - reg
>> +  - interrupts
>> +  - clocks
>> +  - clock-names
>> +  - vdda-1p2-supply
>> +  - vdda-0p9-supply
>> +  - data-lanes
>> +  - ports
>> +
>> +examples:
>> +  - |
>> +    #include <dt-bindings/interrupt-controller/arm-gic.h>
>> +    #include <dt-bindings/clock/qcom,dispcc-sdm845.h>
>> +    #include <dt-bindings/clock/qcom,gcc-sdm845.h>
>> +    msm_dp: displayport-controller@ae90000{
>> +        compatible = "qcom,dp-display";
>> +        cell-index = <0>;
>> +        reg = <0 0xae90000 0 0x1400>;
>> +        reg-names = "dp_controller";
>> +
>> +        interrupt-parent = <&display_subsystem>;
>> +        interrupts = <12 0>;
>> +
>> +        clocks = <&dispcc DISP_CC_MDSS_DP_AUX_CLK>,
>> +                 <&dispcc DISP_CC_MDSS_DP_LINK_CLK>,
>> +                 <&dispcc DISP_CC_MDSS_DP_LINK_INTF_CLK>,
>> +                 <&dispcc DISP_CC_MDSS_DP_PIXEL_CLK>,
>> +                 <&dispcc DISP_CC_MDSS_DP_PIXEL_CLK_SRC>;
>> +        clock-names = "core_aux",
>> +                      "ctrl_link",
>> +                      "ctrl_link_iface", "stream_pixel",
>> +                      "pixel_rcg";
>> +        #clock-cells = <1>;
>> +
>> +        vdda-1p2-supply = <&vreg_l3c_1p2>;
>> +        vdda-0p9-supply = <&vreg_l4a_0p8>;
>> +
>> +        data-lanes = <0 1>;
>> +
>> +        ports {
>> +            #address-cells = <1>;
>> +            #size-cells = <0>;
>> +
>> +            port@0 {
>> +                reg = <0>;
>> +                dp_in: endpoint {
>> +                    remote-endpoint = <&dpu_intf0_out>;
>> +                };
>> +            };
>> +
>> +            port@1 {
>> +                reg = <1>;
>> +                dp_out: endpoint {
>> +                };
>> +            };
>> +        };
>> +    };
> 
> I believe there should be a '...' here.
I think you mean signature is missing? If not could you please explain?
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