Re: [PATCH v8 02/29] drm/msm/dp: add support to send ACT packets for MST

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential
issue to consider:
- [Medium] drm/msm/dp: pixel clock leak on error in
  msm_dp_ctrl_on_stream()
--

commit 87df8767e6c3210a012dfaba1dae900d3f34cb90
Author: Abhinav Kumar <quic_abhinavk@quicinc.com>

drm/msm/dp: add support to send ACT packets for MST

This commit adds REG_DP_MST_ACT and msm_dp_ctrl_mst_send_act() to trigger
and poll the MST action control sequence when enabling or disabling a DP
stream in MST mode.

> diff --git a/drivers/gpu/drm/msm/dp/dp_ctrl.c b/drivers/gpu/drm/msm/dp/dp_ctrl.c
> index 32d4d5743eb36..288f84c33275f 100644
> --- a/drivers/gpu/drm/msm/dp/dp_ctrl.c
> +++ b/drivers/gpu/drm/msm/dp/dp_ctrl.c

[ ... ]

> @@ -2666,6 +2701,10 @@ 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;
> +
>  	ret = msm_dp_ctrl_wait4video_ready(ctrl);
>  	if (ret)
>  		return ret;

[Severity: Medium]
Does returning early here (or on the existing msm_dp_ctrl_wait4video_ready()
error path below) leak the stream pixel clock enabled earlier in
msm_dp_ctrl_on_stream() by msm_dp_ctrl_on_pixel_clk()?

When msm_dp_ctrl_on_stream() fails, msm_dp_display_enable() leaves
msm_dp_display->power_on false, so msm_dp_display_disable() returns early
without calling msm_dp_ctrl_off_pixel_clk().  That leaves
ctrl->pixel_clk[panel->stream_id] prepared and enabled and
ctrl->stream_clks_on[panel->stream_id] set to true, causing subsequent
calls to msm_dp_ctrl_on_pixel_clk() for that stream to hit WARN_ON_ONCE()
and fail with -EINVAL.

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20261110-msm-dp-mst-v8-0-d040fb33db5f@oss.qualcomm.com?part=2