Re: [PATCH RESEND v5 05/25] drm/msm/dp: add support to send ACT packets for MST

[Dmitry Baryshkov]

On Mon, Jun 29, 2026 at 10:14:26PM +0800, Yongxing Mou wrote:
> From: Abhinav Kumar <quic_abhinavk@xxxxxxxxxxx>
> 
> Whenever virtual channel slot allocation changes, the DP
> source must send the action control trigger sequence to notify
> the sink about the same. This would be applicable during the
> start and stop of the pixel stream. Add the infrastructure
> to be able to send ACT packets for the DP controller when
> operating in MST mode.
> 
> Signed-off-by: Abhinav Kumar <quic_abhinavk@xxxxxxxxxxx>
> Signed-off-by: Yongxing Mou <yongxing.mou@xxxxxxxxxxxxxxxx>
> ---
>  drivers/gpu/drm/msm/dp/dp_ctrl.c    | 44 ++++++++++++++++++++++++++++++++++++-
>  drivers/gpu/drm/msm/dp/dp_ctrl.h    |  5 ++++-
>  drivers/gpu/drm/msm/dp/dp_display.c |  3 ++-
>  drivers/gpu/drm/msm/dp/dp_display.h |  1 +
>  drivers/gpu/drm/msm/dp/dp_reg.h     |  2 ++
>  5 files changed, 52 insertions(+), 3 deletions(-)
> 
> @@ -2623,6 +2656,8 @@ int msm_dp_ctrl_on_stream(struct msm_dp_ctrl *msm_dp_ctrl, struct msm_dp_panel *
>  
>  	ctrl = container_of(msm_dp_ctrl, struct msm_dp_ctrl_private, msm_dp_ctrl);
>  
> +	ctrl->mst_active = mst_active;
> +
>  	pixel_rate_orig = panel->msm_dp_mode.drm_mode.clock;
>  	pixel_rate = pixel_rate_orig;
>  
> @@ -2658,6 +2693,10 @@ int msm_dp_ctrl_on_stream(struct msm_dp_ctrl *msm_dp_ctrl, struct msm_dp_panel *
>  
>  	msm_dp_write_link(ctrl, REG_DP_STATE_CTRL, DP_STATE_CTRL_SEND_VIDEO);
>  
> +	ret = msm_dp_ctrl_mst_send_act(msm_dp_ctrl, panel);
> +	if (ret)
> +		return ret;

Should not we mark mst_active only here?

> +
>  	ret = msm_dp_ctrl_wait4video_ready(ctrl);
>  	if (ret)
>  		return ret;
> diff --git a/drivers/gpu/drm/msm/dp/dp_reg.h b/drivers/gpu/drm/msm/dp/dp_reg.h
> index 310e5a1cc934..6808965878d4 100644
> --- a/drivers/gpu/drm/msm/dp/dp_reg.h
> +++ b/drivers/gpu/drm/msm/dp/dp_reg.h
> @@ -156,6 +156,8 @@
>  #define DP_CONFIGURATION_CTRL_BPC_SHIFT		(0x08)
>  #define DP_CONFIGURATION_CTRL_LSCLK_DIV_SHIFT	(0x0D)
>  
> +#define REG_DP_MST_ACT				(0x00000500)

It's not that it is a register in its own register space.

> +
>  #define REG_DP_SOFTWARE_MVID			(0x00000010)
>  #define REG_DP_SOFTWARE_NVID			(0x00000018)
>  #define REG_DP_TOTAL_HOR_VER			(0x0000001C)
> 
> -- 
> 2.43.0
> 

-- 
With best wishes
Dmitry