Commit c352d1ba authored by Imre Deak's avatar Imre Deak Committed by Jani Nikula

drm/i915: vlv: fix IRQ masking when uninstalling interrupts

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 950eabaf
Author: Imre Deak <imre.deak@intel.com>
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@vger.kernel.org (v3.15+)
Signed-off-by: default avatarImre Deak <imre.deak@intel.com>
Reviewed-by: default avatarVille Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: default avatarJani Nikula <jani.nikula@intel.com>
parent 9f49c376
...@@ -3609,7 +3609,7 @@ static void vlv_display_irq_uninstall(struct drm_i915_private *dev_priv) ...@@ -3609,7 +3609,7 @@ static void vlv_display_irq_uninstall(struct drm_i915_private *dev_priv)
vlv_display_irq_reset(dev_priv); vlv_display_irq_reset(dev_priv);
dev_priv->irq_mask = 0; dev_priv->irq_mask = ~0;
} }
static void valleyview_irq_uninstall(struct drm_device *dev) static void valleyview_irq_uninstall(struct drm_device *dev)
......
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