linux-kernel - Re: [PATCH v3 13/38] drm/msm/dp: introduce stream

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Message-ID: <wvctskhoyphicaymbm5b6kermvubhrn5u6uzui3pqf7p3a7ia2@zirqohupflvp>
Date: Mon, 25 Aug 2025 20:56:14 +0300
From: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
To: Yongxing Mou <yongxing.mou@....qualcomm.com>
Cc: Rob Clark <robin.clark@....qualcomm.com>,
        Dmitry Baryshkov <lumag@...nel.org>,
        Abhinav Kumar <abhinav.kumar@...ux.dev>,
        Jessica Zhang <jessica.zhang@....qualcomm.com>,
        Sean Paul <sean@...rly.run>,
        Marijn Suijten <marijn.suijten@...ainline.org>,
        David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
        linux-arm-msm@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        freedreno@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        Abhinav Kumar <quic_abhinavk@...cinc.com>
Subject: Re: [PATCH v3 13/38] drm/msm/dp: introduce stream_id for each DP
 panel

On Mon, Aug 25, 2025 at 10:15:59PM +0800, Yongxing Mou wrote:
> From: Abhinav Kumar <quic_abhinavk@...cinc.com>
> 
> With MST, each DP controller can handle multiple streams.
> There shall be one dp_panel for each stream but the dp_display
> object shall be shared among them. To represent this abstraction,
> create a stream_id for each DP panel which shall be set by the
> MST stream. For SST, default this to stream 0.
> 
> Use the stream ID to control the pixel clock of that respective
> stream by extending the clock handles and state tracking of the
> DP pixel clock to an array of max supported streams. The maximum
> streams currently is 4.
> 
> Signed-off-by: Abhinav Kumar <quic_abhinavk@...cinc.com>
> Signed-off-by: Yongxing Mou <yongxing.mou@....qualcomm.com>
> ---
>  drivers/gpu/drm/msm/dp/dp_ctrl.c    | 58 ++++++++++++++++++++++---------------
>  drivers/gpu/drm/msm/dp/dp_ctrl.h    |  3 +-
>  drivers/gpu/drm/msm/dp/dp_display.c | 27 +++++++++++++++--
>  drivers/gpu/drm/msm/dp/dp_display.h |  2 ++
>  drivers/gpu/drm/msm/dp/dp_panel.h   | 11 +++++++
>  5 files changed, 73 insertions(+), 28 deletions(-)

> @@ -2677,10 +2675,11 @@ static const char *ctrl_clks[] = {
>  	"ctrl_link_iface",
>  };
>  
> -static int msm_dp_ctrl_clk_init(struct msm_dp_ctrl *msm_dp_ctrl)
> +static int msm_dp_ctrl_clk_init(struct msm_dp_ctrl *msm_dp_ctrl, int max_stream)
>  {
>  	struct msm_dp_ctrl_private *ctrl;
>  	struct device *dev;
> +	char stream_id_str[15];

A comment would be nice. Or better replace this with the array lookup,
it's much easier than snprintf.

>  	int i, rc;
>  
>  	ctrl = container_of(msm_dp_ctrl, struct msm_dp_ctrl_private, msm_dp_ctrl);
> @@ -2710,9 +2709,19 @@ static int msm_dp_ctrl_clk_init(struct msm_dp_ctrl *msm_dp_ctrl)
>  	if (rc)
>  		return rc;
>  
> -	ctrl->pixel_clk = devm_clk_get(dev, "stream_pixel");
> -	if (IS_ERR(ctrl->pixel_clk))
> -		return PTR_ERR(ctrl->pixel_clk);
> +	ctrl->pixel_clk[DP_STREAM_0] = devm_clk_get(dev, "stream_pixel");
> +	if (IS_ERR(ctrl->pixel_clk[DP_STREAM_0]))
> +		return PTR_ERR(ctrl->pixel_clk[DP_STREAM_0]);
> +
> +	for (i = DP_STREAM_1; i < max_stream; i++) {
> +		sprintf(stream_id_str, "stream_%d_pixel", i);
> +		ctrl->pixel_clk[i] = devm_clk_get(dev, stream_id_str);
> +
> +		if (IS_ERR(ctrl->pixel_clk[i])) {
> +			DRM_DEBUG_DP("failed to get stream %d pixel clock", i);
> +			break;
> +		}
> +	}
>  
>  	return 0;
>  }

-- 
With best wishes
Dmitry