• Imre Deak's avatar
    drm/i915: vlv: fix IRQ masking when uninstalling interrupts · 1eadc8e9
    Imre Deak authored
    commit c352d1ba upstream.
    
    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=85920Signed-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>
    [ luis: backported to 3.16: adjusted context ]
    Signed-off-by: default avatarLuis Henriques <luis.henriques@canonical.com>
    1eadc8e9
i915_irq.c 126 KB