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drm/i915: capture last_vblank count at IRQ uninstall time too

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In dc1336ff4f (set vblank enable flag correctly
across IRQ uninstall), we made sure drivers that uninstall their interrupt
handler set the vblank enabled flag correctly, so that when interrupts are
re-enabled, vblank interrupts & counts work as expected.  However I missed the
last_vblank field:  it needs to be updated as well, otherwise, at the next
drm_update_vblank_count we'll end up comparing a current count to a stale
one (the last one captured by the disable function), which may trigger the
wraparound handling, leading to a jumpy counter and hangs in drm_wait_vblank.

The jumpy counter can prevent the DRM_WAIT_ON from returning success if the
difference between the current count and the requested count is greater than
2^23, leading to timeouts or hangs, if the ioctl is restarted in a loop (as
is the case in libdrm < 2.4.4).

Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Acked-by: Michel Dänzer <michel@daenzer.net>
Tested-by: Timo Aaltonen <tjaalton@cc.hut.fi>
Signed-off-by: Dave Airlie <airlied@redhat.com>
This commit is contained in:
Jesse Barnes 2009-02-06 13:04:49 -08:00 committed by Dave Airlie
parent 7d8d58b23f
commit 14d200c5e5
1 changed files with 1 additions and 0 deletions
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1
drivers/gpu/drm/drm_irq.c
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@ -276,6 +276,7 @@ int drm_irq_uninstall(struct drm_device * dev)
for (i = 0; i < dev->num_crtcs; i++) {
DRM_WAKEUP(&dev->vbl_queue[i]);
dev->vblank_enabled[i] = 0;
dev->last_vblank[i] = dev->driver->get_vblank_counter(dev, i);
}
spin_unlock_irqrestore(&dev->vbl_lock, irqflags);