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Commit 802c7eb6 authored by Jesse Barnes's avatar Jesse Barnes Committed by Eric Anholt
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drm/i915: sanity check IER at wait_request time 



We might sleep here anyway so I hope an extra uncached read is ok to
add.

In #20896 we found that vbetool clobbers the IER.  In KMS mode this is
particularly bad since we don't set the interrupt regs late (in
EnterVT), so we'd fail to get *any* interrupts at all after X started
(since some distros have scripts that call vbetool at X startup
apparently).

So this patch checks IER at wait_request time, and re-enables
interrupts if it's been clobbered.  In a proper config this check
should never be triggered.

This is really a distro issue, but having a sanity check is nice, as
long as it doesn't have a real performance hit.

Tested-by: default avatarMateusz Kaduk <mateusz.kaduk@gmail.com>
Signed-off-by: default avatarJesse Barnes <jbarnes@virtuousgeek.org>
[anholt: Moved the check inside of the sleeping case to avoid perf cost]
Signed-off-by: default avatarEric Anholt <eric@anholt.net>
parent 0ba0e9e1

drivers/gpu/drm/i915/i915_gem.c

+9 −0
Original line number Diff line number Diff line
@@ -1691,11 +1691,20 @@ static int 
i915_wait_request(struct drm_device *dev, uint32_t seqno)

{

	drm_i915_private_t *dev_priv = dev->dev_private;

	u32 ier;

	int ret = 0;



	BUG_ON(seqno == 0);



	if (!i915_seqno_passed(i915_get_gem_seqno(dev), seqno)) {

		ier = I915_READ(IER);

		if (!ier) {

			DRM_ERROR("something (likely vbetool) disabled "

				  "interrupts, re-enabling\n");

			i915_driver_irq_preinstall(dev);

			i915_driver_irq_postinstall(dev);

		}



		dev_priv->mm.waiting_gem_seqno = seqno;

		i915_user_irq_get(dev);

		ret = wait_event_interruptible(dev_priv->irq_queue,