[Intel-gfx] [PATCH 15/19] drm: Update vblank->last in drm_update_vblank_count()

[Daniel Vetter]

On Wed, Aug 06, 2014 at 02:49:58PM +0300, ville.syrjala at linux.intel.com wrote:
> From: Ville Syrjälä <ville.syrjala at linux.intel.com>
> 
> We should update the last in drm_update_vblank_count() to avoid applying
> the diff more than once. This could occur eg. if drm_vblank_off() gets
> called multiple times for the crtc.
> 
> Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>

Currently we update ->last when disabling the vblank and use it when
re-enabling it. Those calls should be symmetric, except for driver bugs.
Imo would be better to tighten up the checks for that.

Or do I completely misunderstand what's going on here?
-Daniel

> ---
>  drivers/gpu/drm/drm_irq.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/gpu/drm/drm_irq.c b/drivers/gpu/drm/drm_irq.c
> index 0523f5b..67507a4 100644
> --- a/drivers/gpu/drm/drm_irq.c
> +++ b/drivers/gpu/drm/drm_irq.c
> @@ -109,6 +109,8 @@ static void drm_update_vblank_count(struct drm_device *dev, int crtc)
>  	if (diff == 0)
>  		return;
>  
> +	vblank->last = cur_vblank;
> +
>  	/* Reinitialize corresponding vblank timestamp if high-precision query
>  	 * available. Skip this step if query unsupported or failed. Will
>  	 * reinitialize delayed at next vblank interrupt in that case.
> -- 
> 1.8.5.5
> 
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-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch