linux-kernel - Re: [RFC PATCH 02/13] dt-bindings: msm/dsi: Document Display Stream Compression (DSC) parameters

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Message-ID: <20210521144237.GZ2484@yoga>
Date:   Fri, 21 May 2021 09:42:37 -0500
From:   Bjorn Andersson <bjorn.andersson@...aro.org>
To:     Vinod Koul <vkoul@...nel.org>
Cc:     Rob Clark <robdclark@...il.com>, linux-arm-msm@...r.kernel.org,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Jonathan Marek <jonathan@...ek.ca>,
        Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
        Abhinav Kumar <abhinavk@...eaurora.org>,
        linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        freedreno@...ts.freedesktop.org, Rob Herring <robh+dt@...nel.org>,
        devicetree@...r.kernel.org
Subject: Re: [RFC PATCH 02/13] dt-bindings: msm/dsi: Document Display Stream
 Compression (DSC) parameters

On Fri 21 May 07:49 CDT 2021, Vinod Koul wrote:

> DSC enables streams to be compressed before we send to panel. This
> requires DSC enabled encoder and a panel to be present. So we add this
> information in board DTS and find if DSC can be enabled and the
> parameters required to configure DSC are added to binding document along
> with example
> 
> Signed-off-by: Vinod Koul <vkoul@...nel.org>
> ---
>  .../devicetree/bindings/display/msm/dsi.txt       | 15 +++++++++++++++
>  1 file changed, 15 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/display/msm/dsi.txt b/Documentation/devicetree/bindings/display/msm/dsi.txt
> index b9a64d3ff184..83d2fb92267e 100644
> --- a/Documentation/devicetree/bindings/display/msm/dsi.txt
> +++ b/Documentation/devicetree/bindings/display/msm/dsi.txt
> @@ -48,6 +48,13 @@ Optional properties:
>  - pinctrl-n: the "sleep" pinctrl state
>  - ports: contains DSI controller input and output ports as children, each
>    containing one endpoint subnode.
> +- qcom,mdss-dsc-enabled: Display Stream Compression (DSC) is enabled
> +- qcom,mdss-slice-height: DSC slice height in pixels
> +- qcom,mdss-slice-width: DSC slice width in pixels
> +- qcom,mdss-slice-per-pkt: DSC slices per packet
> +- qcom,mdss-bit-per-component: DSC bits per component
> +- qcom,mdss-bit-per-pixel: DSC bits per pixel
> +- qcom,mdss-block-prediction-enable: Block prediction mode of DSC enabled
>  
>    DSI Endpoint properties:
>    - remote-endpoint: For port@0, set to phandle of the connected panel/bridge's
> @@ -188,6 +195,14 @@ Example:
>  		qcom,master-dsi;
>  		qcom,sync-dual-dsi;
>  
> +		qcom,mdss-dsc-enabled;

To me the activation of DSC seems to be a property of the panel.

> +		qcom,mdss-slice-height = <16>;
> +		qcom,mdss-slice-width = <540>;
> +		qcom,mdss-slice-per-pkt = <1>;
> +		qcom,mdss-bit-per-component = <8>;
> +		qcom,mdss-bit-per-pixel = <8>;
> +		qcom,mdss-block-prediction-enable;

Which of these properties relates to the DSC encoder and what needs to
be agreed with the sink? Can't we derive e.g. bpp from the information
we have from the attached panel already?

Regards,
Bjorn

> +
>  		qcom,mdss-mdp-transfer-time-us = <12000>;
>  
>  		pinctrl-names = "default", "sleep";
> -- 
> 2.26.3
>