On Fri, Jan 12, 2018 at 01:57:03PM -0800, Dhinakaran Pandiyan wrote:
> drm_vblank_count() has a u32 type returning what is a 64-bit vblank count.
> The effect of this is when drm_wait_vblank_ioctl() tries to widen the user
> space requested vblank sequence using this clipped 32-bit count(when the
> value is >= 2^32) as reference, the requested sequence remains a 32-bit
> value and gets queued like that. However, the code that checks if the
> requested sequence has passed compares this against the 64-bit vblank
> count.
>
> Cc: Keith Packard <keithp@xxxxxxxxxx>
> Cc: Michel Dänzer <michel@xxxxxxxxxxx>
> Cc: Daniel Vetter <daniel@xxxxxxxx>
> Signed-off-by: Dhinakaran Pandiyan <dhinakaran.pandiyan@xxxxxxxxx>
Sounds like the 64bit widening wasn't all that well tested ... do we have
an igt for this? Iirc the base igt was merged already.
-Daniel
> ---
> drivers/gpu/drm/drm_vblank.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/drm_vblank.c b/drivers/gpu/drm/drm_vblank.c
> index 32d9bcf5be7f..768a8e44d99b 100644
> --- a/drivers/gpu/drm/drm_vblank.c
> +++ b/drivers/gpu/drm/drm_vblank.c
> @@ -271,7 +271,7 @@ static void drm_update_vblank_count(struct drm_device *dev, unsigned int pipe,
> store_vblank(dev, pipe, diff, t_vblank, cur_vblank);
> }
>
> -static u32 drm_vblank_count(struct drm_device *dev, unsigned int pipe)
> +static u64 drm_vblank_count(struct drm_device *dev, unsigned int pipe)
> {
> struct drm_vblank_crtc *vblank = &dev->vblank[pipe];
>
> --
> 2.11.0
>
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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