linux-kernel - Re: [PATCH 03/19] drm/msm/dp: Return early from atomic

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Message-ID: <mw6wrx3nsiantc2sweio2xbgrranoglzugaykjo3robkknrlzj@5dma4fm57xut>
Date: Mon, 14 Jul 2025 14:47:43 +0300
From: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
To: Jessica Zhang <jessica.zhang@....qualcomm.com>
Cc: Rob Clark <robin.clark@....qualcomm.com>,
        Abhinav Kumar <abhinav.kumar@...ux.dev>,
        Dmitry Baryshkov <lumag@...nel.org>, 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,
        Yongxing Mou <quic_yongmou@...cinc.com>
Subject: Re: [PATCH 03/19] drm/msm/dp: Return early from atomic_enable() if
 cable is not connected

On Fri, Jul 11, 2025 at 05:58:08PM -0700, Jessica Zhang wrote:
> Replace the ST_MAINLINK_READY check here with a check for if the cable
> is not connected.
> 
> Since atomic_check() fails if the link isn't ready, we technically don't
> need a check against ST_MAINLINK_READY. The hpd_state should also never
> really hit ST_DISPLAY_OFF since atomic_enable() shouldn't be called
> twice in a row without an atomic_enable() in between.

There is something wrong in the last sentence.

> 
> That being said, it is possible for the cable to be disconnected after
> atomic_check() but before atomic_enable(). So let's change this check to
> guard against msm_dp::connected instead.
> 
> Signed-off-by: Jessica Zhang <jessica.zhang@....qualcomm.com>
> ---
>  drivers/gpu/drm/msm/dp/dp_display.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/msm/dp/dp_display.c b/drivers/gpu/drm/msm/dp/dp_display.c
> index 1072b5fc00ae..fe38ea868eda 100644
> --- a/drivers/gpu/drm/msm/dp/dp_display.c
> +++ b/drivers/gpu/drm/msm/dp/dp_display.c
> @@ -1606,7 +1606,7 @@ void msm_dp_bridge_atomic_enable(struct drm_bridge *drm_bridge,
>  	}
>  
>  	hpd_state = msm_dp_display->hpd_state;
> -	if (hpd_state != ST_DISPLAY_OFF && hpd_state != ST_MAINLINK_READY) {
> +	if (!dp->connected) {
>  		mutex_unlock(&msm_dp_display->event_mutex);
>  		return;
>  	}
> 
> -- 
> 2.50.1
> 

-- 
With best wishes
Dmitry