[PATCH v3 12/38] drm/msm/dp: introduce max_streams for DP controller MST support

[Dmitry Baryshkov]

On Mon, Aug 25, 2025 at 10:15:58PM +0800, Yongxing Mou wrote:
> From: Abhinav Kumar <quic_abhinavk at quicinc.com>
> 
> 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`).
> 
> This change also accounts for platforms with asymmetric stream support,
> e.g., DP0 supporting 4 streams and DP1 supporting 2.

How?

> 
> Signed-off-by: Abhinav Kumar <quic_abhinavk at quicinc.com>
> Signed-off-by: Yongxing Mou <yongxing.mou at oss.qualcomm.com>
> ---
>  drivers/gpu/drm/msm/dp/dp_display.c | 21 +++++++++++++++++++++
>  drivers/gpu/drm/msm/dp/dp_display.h |  1 +
>  2 files changed, 22 insertions(+)
> 
> diff --git a/drivers/gpu/drm/msm/dp/dp_display.c b/drivers/gpu/drm/msm/dp/dp_display.c
> index 78d932bceb581ee54116926506b1025bd159108f..a8477a0a180137f15cbb1401c3964636aa32626c 100644
> --- a/drivers/gpu/drm/msm/dp/dp_display.c
> +++ b/drivers/gpu/drm/msm/dp/dp_display.c
> @@ -33,6 +33,7 @@ module_param(psr_enabled, bool, 0);
>  MODULE_PARM_DESC(psr_enabled, "enable PSR for eDP and DP displays");
>  
>  #define HPD_STRING_SIZE 30
> +#define DEFAULT_STREAM_COUNT 1
>  
>  enum {
>  	ISR_DISCONNECTED,
> @@ -52,6 +53,7 @@ struct msm_dp_display_private {
>  	bool core_initialized;
>  	bool phy_initialized;
>  	bool audio_supported;
> +	bool mst_supported;

Why do we need the separate boot field here? Isn't it enough to check the max_stream?

>  
>  	struct drm_device *drm_dev;
>  
> @@ -84,12 +86,15 @@ struct msm_dp_display_private {
>  
>  	void __iomem *p0_base;
>  	size_t p0_len;
> +
> +	int max_stream;
>  };
>  
>  struct msm_dp_desc {
>  	phys_addr_t io_start;
>  	unsigned int id;
>  	bool wide_bus_supported;
> +	int mst_streams;
>  };
>  
>  static const struct msm_dp_desc msm_dp_desc_sa8775p[] = {
> @@ -1213,6 +1218,15 @@ static int msm_dp_display_get_io(struct msm_dp_display_private *display)
>  	return 0;
>  }
>  
> +int msm_dp_get_mst_max_stream(struct msm_dp *msm_dp_display)
> +{
> +	struct msm_dp_display_private *dp;
> +
> +	dp = container_of(msm_dp_display, struct msm_dp_display_private, msm_dp_display);
> +
> +	return dp->max_stream;
> +}
> +
>  static int msm_dp_display_probe(struct platform_device *pdev)
>  {
>  	int rc = 0;
> @@ -1239,6 +1253,13 @@ 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 = DEFAULT_STREAM_COUNT;

Just use 1 it's not that magic to define it.

> +	dp->mst_supported = FALSE;
> +
> +	if (desc->mst_streams > DEFAULT_STREAM_COUNT) {
> +		dp->max_stream = desc->mst_streams;
> +		dp->mst_supported = TRUE;
> +	}
>  
>  	rc = msm_dp_display_get_io(dp);
>  	if (rc)
> diff --git a/drivers/gpu/drm/msm/dp/dp_display.h b/drivers/gpu/drm/msm/dp/dp_display.h
> index 37c6e87db90ce951274cdae61f26d76dc9ef3840..7727cf325a89b4892d2370a5616c4fa76fc88485 100644
> --- a/drivers/gpu/drm/msm/dp/dp_display.h
> +++ b/drivers/gpu/drm/msm/dp/dp_display.h
> @@ -29,6 +29,7 @@ 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);
> 
> -- 
> 2.34.1
> 

-- 
With best wishes
Dmitry