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H A Di915_irq.cdiff c352d1ba1e1e2c8a96af660944a58e86b12ac4af Thu Nov 20 08:05:55 CST 2014 Imre Deak <imre.deak@intel.com> 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 950eabaf5a87257040e0c207be09487954113f54
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: Imre Deak <imre.deak@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
diff 950eabaf5a87257040e0c207be09487954113f54 Mon Sep 08 07:21:09 CDT 2014 Imre Deak <imre.deak@intel.com> drm/i915: vlv: fix display IRQ enable/disable

We want to enable/disable display IRQs only if global i915 IRQs are
enabled. To check the latter it's not enough to consult the DRM
dev->irq_enabled flag, since runtime PM can disable/enable IRQs
and it won't adjust this flag only the i915 specific
dev_priv->pm._irqs_disabled flag. Fix this by using the proper
intel_irqs_enabled() helper instead.

Fortunately this didn't cause an actual problem since even if we enabled
display IRQs too early (before enabling global i915 IRQs) the
VLV_MASTER_IER would still be clear masking all IRQs.

This issue was caught by

commit 920dd15a2b2fc60d054646a8a1ffd6aeb6090e05
Author: Daniel Vetter <daniel.vetter@ffwll.ch>
Date: Wed Aug 27 10:43:37 2014 +0200

drm/i915: WARN if interrupts aren't on in en/disable_pipestat

Signed-off-by: Imre Deak <imre.deak@intel.com>
Cc: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>