On Tue, May 26, 2015 at 05:53:38PM +0900, Michel Dänzer wrote:
> From: Michel Dänzer <michel.daenzer@xxxxxxx>
>
> dev->max_vblank_count contains the largest value that can be represented
> by the hardware counter. When the hardware counter wraps around, we have
> to add that value + 1 to get the same value as if the hardware counter
> didn't wrap around.
>
> Signed-off-by: Michel Dänzer <michel.daenzer@xxxxxxx>
Well there's two users of this really, one wants the max (this one here)
and the other a mask. And all the drivers use it as a mask. Maybe rename
it to vblank_counter_mask or similar while at it to prevent further
confusion?
-Daniel
> ---
> drivers/gpu/drm/drm_irq.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_irq.c b/drivers/gpu/drm/drm_irq.c
> index c8a3447..f9634da 100644
> --- a/drivers/gpu/drm/drm_irq.c
> +++ b/drivers/gpu/drm/drm_irq.c
> @@ -100,7 +100,7 @@ static void drm_update_vblank_count(struct drm_device *dev, int crtc)
> /*
> * Interrupts were disabled prior to this call, so deal with counter
> * wrap if needed.
> - * NOTE! It's possible we lost a full dev->max_vblank_count events
> + * NOTE! It's possible we lost a full dev->max_vblank_count + 1 events
> * here if the register is small or we had vblank interrupts off for
> * a long time.
> *
> @@ -117,7 +117,7 @@ static void drm_update_vblank_count(struct drm_device *dev, int crtc)
> /* Deal with counter wrap */
> diff = cur_vblank - vblank->last;
> if (cur_vblank < vblank->last) {
> - diff += dev->max_vblank_count;
> + diff += dev->max_vblank_count + 1;
>
> DRM_DEBUG("last_vblank[%d]=0x%x, cur_vblank=0x%x => diff=0x%x\n",
> crtc, vblank->last, cur_vblank, diff);
> --
> 2.1.4
>
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--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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