On Wed, 2013-06-12 at 11:58 +0200, Michel Dänzer wrote:
> From: Michel Dänzer <michel.daenzer@xxxxxxx>
>
> It takes an unsigned value. This happens not to blow up on 64-bit
> architectures, but it does on 32-bit, causing
> drm_calc_vbltimestamp_from_scanoutpos() to calculate totally bogus
> timestamps for vblank events. Which in turn causes e.g. gnome-shell to
> hang after a DPMS off cycle with current xf86-video-ati Git.
>
> Cc: stable@xxxxxxxxxxxxxxx
> Signed-off-by: Michel Dänzer <michel.daenzer@xxxxxxx>
Yes, I introduced this regression in:
drm: use monotonic time in drm_calc_vbltimestamp_from_scanoutpos
The fix seems to be ok, perhaps you should also mention the regressing
commit in the commit message.
Reviewed-by: Imre Deak <imre.deak@xxxxxxxxx>
> ---
> drivers/gpu/drm/drm_irq.c | 5 ++++-
> 1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/drm_irq.c b/drivers/gpu/drm/drm_irq.c
> index a6a8643..39665f8 100644
> --- a/drivers/gpu/drm/drm_irq.c
> +++ b/drivers/gpu/drm/drm_irq.c
> @@ -708,7 +708,10 @@ int drm_calc_vbltimestamp_from_scanoutpos(struct drm_device *dev, int crtc,
> /* Subtract time delta from raw timestamp to get final
> * vblank_time timestamp for end of vblank.
> */
> - etime = ktime_sub_ns(etime, delta_ns);
> + if (delta_ns < 0)
> + etime = ktime_add_ns(etime, -delta_ns);
> + else
> + etime = ktime_sub_ns(etime, delta_ns);
> *vblank_time = ktime_to_timeval(etime);
>
> DRM_DEBUG("crtc %d : v %d p(%d,%d)@ %ld.%ld -> %ld.%ld [e %d us, %d rep]\n",
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