Re: [PATCH v3 2/4] drm/imx: notify drm core before sending event during crtc disable

[Daniel Vetter]

On Tue, Jun 25, 2019 at 06:59:13PM +0100, Robert Beckett wrote:
> Notify drm core before sending pending events during crtc disable.
> This fixes the first event after disable having an old stale timestamp
> by having drm_crtc_vblank_off update the timestamp to now.
> 
> This was seen while debugging weston log message:
> Warning: computed repaint delay is insane: -8212 msec
> 
> This occured due to:
> 1. driver starts up
> 2. fbcon comes along and restores fbdev, enabling vblank
> 3. vblank_disable_fn fires via timer disabling vblank, keeping vblank
> seq number and time set at current value
> (some time later)
> 4. weston starts and does a modeset
> 5. atomic commit disables crtc while it does the modeset
> 6. ipu_crtc_atomic_disable sends vblank with old seq number and time
> 
> Fixes: a474478642d5 ("drm/imx: fix crtc vblank state regression")
> 
> Signed-off-by: Robert Beckett <bob.beckett@xxxxxxxxxxxxx>

Now that I understand what's going on here:

Reviewed-by: Daniel Vetter <daniel.vetter@xxxxxxxx>

> ---
>  drivers/gpu/drm/imx/ipuv3-crtc.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/imx/ipuv3-crtc.c b/drivers/gpu/drm/imx/ipuv3-crtc.c
> index 9cc1d678674f..e04d6efff1b5 100644
> --- a/drivers/gpu/drm/imx/ipuv3-crtc.c
> +++ b/drivers/gpu/drm/imx/ipuv3-crtc.c
> @@ -91,14 +91,14 @@ static void ipu_crtc_atomic_disable(struct drm_crtc *crtc,
>  	ipu_dc_disable(ipu);
>  	ipu_prg_disable(ipu);
>  
> +	drm_crtc_vblank_off(crtc);
> +
>  	spin_lock_irq(&crtc->dev->event_lock);
>  	if (crtc->state->event) {
>  		drm_crtc_send_vblank_event(crtc, crtc->state->event);
>  		crtc->state->event = NULL;
>  	}
>  	spin_unlock_irq(&crtc->dev->event_lock);
> -
> -	drm_crtc_vblank_off(crtc);
>  }
>  
>  static void imx_drm_crtc_reset(struct drm_crtc *crtc)
> -- 
> 2.18.0
> 

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch