Re: [PATCH v2 02/18] drm/exynos: use wait_event_timeout() for safety usage

[Daniel Kurtz <djkurtz@chromium.org>]

On Wed, May 21, 2014 at 12:42 PM, YoungJun Cho <yj44.cho@samsung.com> wrote:
> There could be the case that the page flip operation isn't finished correctly
> with some abnormal condition such as panel reset. So this patch replaces
> wait_event() with wait_event_timeout() to avoid waiting for page flip completion
> infinitely.
> And clears exynos_crtc->pending_flip in exynos_drm_crtc_page_flip() when
> exynos_drm_crtc_mode_set_commit() is failed.
>
> Signed-off-by: YoungJun Cho <yj44.cho@samsung.com>
> Acked-by: Inki Dae <inki.dae@samsung.com>
> Acked-by: Kyungmin Park <kyungmin.park@samsung.com>
> ---
>  drivers/gpu/drm/exynos/exynos_drm_crtc.c |    7 +++++--
>  1 file changed, 5 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/exynos/exynos_drm_crtc.c b/drivers/gpu/drm/exynos/exynos_drm_crtc.c
> index 95c9435..3bf091d 100644
> --- a/drivers/gpu/drm/exynos/exynos_drm_crtc.c
> +++ b/drivers/gpu/drm/exynos/exynos_drm_crtc.c
> @@ -69,8 +69,10 @@ static void exynos_drm_crtc_dpms(struct drm_crtc *crtc, int mode)
>
>         if (mode > DRM_MODE_DPMS_ON) {
>                 /* wait for the completion of page flip. */
> -               wait_event(exynos_crtc->pending_flip_queue,
> -                               atomic_read(&exynos_crtc->pending_flip) == 0);
> +               if (!wait_event_timeout(exynos_crtc->pending_flip_queue,
> +                               !atomic_read(&exynos_crtc->pending_flip),
> +                               HZ/20))
> +                       atomic_set(&exynos_crtc->pending_flip, 0);

I meant that changing this to wait_event_timeout() seems to be masking
the original problem, that pending_flip wasn't being cleared.
Now that you are now clearing pending_flip in the error path, you
don't need the timeout, right?

-Dan

>                 drm_vblank_off(crtc->dev, exynos_crtc->pipe);
>         }
>
> @@ -259,6 +261,7 @@ static int exynos_drm_crtc_page_flip(struct drm_crtc *crtc,
>                         spin_lock_irq(&dev->event_lock);
>                         drm_vblank_put(dev, exynos_crtc->pipe);
>                         list_del(&event->base.link);
> +                       atomic_set(&exynos_crtc->pending_flip, 0);
>                         spin_unlock_irq(&dev->event_lock);
>
>                         goto out;
> --
> 1.7.9.5
>