Re: [PATCH v4 14/39] drm/msm/dp: introduce max_streams for DP controller MST support

[Dmitry Baryshkov]

On Fri, Apr 10, 2026 at 05:33:49PM +0800, Yongxing Mou wrote:
> From: Abhinav Kumar <quic_abhinavk@xxxxxxxxxxx>
> 
> Introduce the `mst_streams` field in each DP controller descriptor to
> specify the number of supported MST streams. Most platforms support 2 or
> 4 MST streams, while platforms without MST support default to a single
> stream (`DEFAULT_STREAM_COUNT = 1`).

There is no such const anymore.

> 
> Also accounts for platforms with asymmetric stream support, e.g., DP0
> supporting 4 streams and DP1 supporting 2.

There is no need to mention it.

> 
> Signed-off-by: Abhinav Kumar <quic_abhinavk@xxxxxxxxxxx>
> Signed-off-by: Yongxing Mou <yongxing.mou@xxxxxxxxxxxxxxxx>
> ---
>  drivers/gpu/drm/msm/dp/dp_ctrl.c    | 20 +++++++++++++++++---
>  drivers/gpu/drm/msm/dp/dp_ctrl.h    |  2 ++
>  drivers/gpu/drm/msm/dp/dp_display.c | 20 +++++++++++++++++++-
>  drivers/gpu/drm/msm/dp/dp_display.h |  1 +
>  4 files changed, 39 insertions(+), 4 deletions(-)
> 
> @@ -2740,7 +2741,8 @@ static int msm_dp_ctrl_clk_init(struct msm_dp_ctrl *msm_dp_ctrl)
>  	if (rc)
>  		return rc;
>  
> -	for (i = DP_STREAM_0; i < DP_STREAM_MAX; i++) {
> +	ctrl->num_pixel_clks = 0;
> +	for (i = DP_STREAM_0; i < max_stream; i++) {

Why? I think the code was fine with getting up to DP_STREAM_MAX clocks.
In fact, I'd rather use that instead of the hardcoded value for
determining how many streams can be there. Think of the old DTs which
didn't have extra stream clocks. We still need to support those.

>  		ctrl->pixel_clk[i] = devm_clk_get(dev, pixel_clks[i]);
>  
>  		if (i == 0 && IS_ERR(ctrl->pixel_clk[i]))
> @@ -2750,14 +2752,26 @@ static int msm_dp_ctrl_clk_init(struct msm_dp_ctrl *msm_dp_ctrl)
>  			DRM_DEBUG_DP("stream %d pixel clock not exist", i);
>  			break;
>  		}
> +
> +		ctrl->num_pixel_clks++;
>  	}
>  
>  	return 0;
>  }
>  
> @@ -1234,6 +1248,10 @@ static int msm_dp_display_probe(struct platform_device *pdev)
>  	dp->msm_dp_display.is_edp =
>  		(dp->msm_dp_display.connector_type == DRM_MODE_CONNECTOR_eDP);
>  	dp->hpd_isr_status = 0;
> +	dp->max_stream = 1;
> +
> +	if (desc->mst_streams > 1)
> +		dp->max_stream = desc->mst_streams;

Here you can assign it from the DT resources.

>  
>  	mutex_init(&dp->plugged_lock);
>  
> diff --git a/drivers/gpu/drm/msm/dp/dp_display.h b/drivers/gpu/drm/msm/dp/dp_display.h
> index a5c6ed5b18e4..b0cfdf215970 100644
> --- a/drivers/gpu/drm/msm/dp/dp_display.h
> +++ b/drivers/gpu/drm/msm/dp/dp_display.h
> @@ -26,6 +26,7 @@ struct msm_dp {
>  	bool psr_supported;
>  };
>  
> +int msm_dp_get_mst_max_stream(struct msm_dp *msm_dp_display);
>  int msm_dp_display_get_modes(struct msm_dp *msm_dp_display);
>  bool msm_dp_display_check_video_test(struct msm_dp *msm_dp_display);
>  int msm_dp_display_get_test_bpp(struct msm_dp *msm_dp_display);
> 
> -- 
> 2.43.0
> 

-- 
With best wishes
Dmitry