linux-kernel - Re: [PATCH v10 3/4] drm/msm/dpu: revise timing engine programming to support widebus feature

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Date:   Fri, 25 Feb 2022 10:13:56 -0800
From:   Stephen Boyd <swboyd@...omium.org>
To:     Kuogee Hsieh <quic_khsieh@...cinc.com>, agross@...nel.org,
        airlied@...ux.ie, bjorn.andersson@...aro.org, daniel@...ll.ch,
        dmitry.baryshkov@...aro.org, dri-devel@...ts.freedesktop.org,
        robdclark@...il.com, sean@...rly.run, vkoul@...nel.org
Cc:     quic_abhinavk@...cinc.com, quic_aravindh@...cinc.com,
        quic_sbillaka@...cinc.com, freedreno@...ts.freedesktop.org,
        linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v10 3/4] drm/msm/dpu: revise timing engine programming to
 support widebus feature

Quoting Kuogee Hsieh (2022-02-22 16:27:39)
> Widebus feature will transmit two pixel data per pixel clock to interface.
> Timing engine provides driving force for this purpose. This patch base
> on HPG (Hardware Programming Guide) to revise timing engine register
> setting to accommodate both widebus and non widebus application. Also
> horizontal width parameters need to be reduced by half since two pixel
> data are clocked out per pixel clock when widebus feature enabled.
>
> Widebus can be enabled individually at DP. However at DSI, widebus have
> to be enabled along with DSC to achieve pixel clock rate be scaled down
> with same ratio as compression ratio when 10 bits per source component.
> Therefore this patch add no supports of DSI related widebus and compression.
>
> Changes in v2:
> -- remove compression related code from timing
> -- remove op_info from  struct msm_drm_private
> -- remove unnecessary wide_bus_en variables
> -- pass wide_bus_en into timing configuration by struct msm_dp
>
> Changes in v3:
> -- split patch into 3 patches
>
> Changes in v4:
> -- rework timing engine to not interfere with dsi/hdmi
> -- cover both widebus and compression
>
> Changes in v5:
> -- remove supports of DSI widebus and compression
>
> Changes in v7:
> -- split this patch into 3 patches
> -- add Tested-by
>
> Changes in v8:
> -- move new registers writes under DATA_HCTL_EN features check.
>
> Changes in v10:
> -- add const inside dpu_encoder_is_widebus_enabled()
> -- drop useless parenthesis please
>
> Signed-off-by: Kuogee Hsieh <quic_khsieh@...cinc.com>
> Tested-by: Bjorn Andersson <bjorn.andersson@...aro.org>
> Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
> ---

Reviewed-by: Stephen Boyd <swboyd@...omium.org>