On Thu, 2014-11-20 at 15:11 +0100, Daniel Vetter wrote: > On Thu, Nov 20, 2014 at 04:05:55PM +0200, Imre Deak wrote: > > irq_mask should include all IRQ bits that we want to mask, but atm we > > set it incorrectly to the inverse of this. If the mask is used > > subsequently to enable/disable some IRQ bits, we may unintentionally > > unmask unrelated IRQs. I can't see any way that this can lead to a real > > problem in the current -nightly code, since the first place the mask > > will be used next (after a suspend/resume cycle) is in > > valleyview_irq_postinstall(), but the mask is reset there to its proper > > value. > > > > This causes a problem in the upstream kernel though, where - due to another > > issue - the mask is used in the above way to disable only the display IRQs. > > This other issue is fixed by: > > > > commit 950eabaf5a87257040e0c207be09487954113f54 > > Author: Imre Deak <imre.deak@xxxxxxxxx> > > Date: Mon Sep 8 15:21:09 2014 +0300 > > > > drm/i915: vlv: fix display IRQ enable/disable > > > > Interestingly, even with the above two bugs, we shouldn't in theory have > > any real problems (arguably a famous last sentence:). That's because > > even if we unmask something unintentionally via the VLV_IMR/VLV_IER > > register the master IRQ masking bit in VLV_MASTER_IER is still set and > > should prevent all i915 interrupts. According to my testing on an ASUS > > T100 with DSI output this isn't the case at least with the > > MIPIA_INTERRUPT. Leaving this one unmasked in IMR/IER, while having > > VLV_MASTER_IER set to 0 may lead to a lockup during system suspend as > > shown in the bugzilla ticket below. This fix should get rid of the > > problem reported there in upstream and older kernels. > > > > Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=85920 > > Cc: stable@xxxxxxxxxxxxxxx (v3.15+) > > Signed-off-by: Imre Deak <imre.deak@xxxxxxxxx> > > --- > > drivers/gpu/drm/i915/i915_irq.c | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c > > index 8d169e1..4601f53 100644 > > --- a/drivers/gpu/drm/i915/i915_irq.c > > +++ b/drivers/gpu/drm/i915/i915_irq.c > > @@ -3597,7 +3597,7 @@ static void vlv_display_irq_uninstall(struct drm_i915_private *dev_priv) > > > > vlv_display_irq_reset(dev_priv); > > > > - dev_priv->irq_mask = 0; > > + dev_priv->irq_mask = ~0; > > vlv seems to be the only platform which resets irq masks in the uninstall > hook. That smells fishy - can't we just remove this completely? Yes, we can look into removing it. But on older kernels the irq_mask was used in the way I described in the commit log, so I'd suggest this fix for -stable at least, together with commit 950eabaf5 which isn't upstream yet. > -Daniel -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html