• I
    drm/i915: avoid processing spurious/shared interrupts in low-power states · 2dd2a883
    Imre Deak 提交于
    Atm, it's possible that the interrupt handler is called when the device
    is in D3 or some other low-power state. It can be due to another device
    that is still in D0 state and shares the interrupt line with i915, or on
    some platforms there could be spurious interrupts even without sharing
    the interrupt line. The latter case was reported by Klaus Ethgen using a
    Lenovo x61p machine (gen 4). He noticed this issue via a system
    suspend/resume hang and bisected it to the following commit:
    
    commit e11aa362
    Author: Jesse Barnes <jbarnes@virtuousgeek.org>
    Date:   Wed Jun 18 09:52:55 2014 -0700
    
        drm/i915: use runtime irq suspend/resume in freeze/thaw
    
    This is a problem, since in low-power states IIR will always read
    0xffffffff resulting in an endless IRQ servicing loop.
    
    Fix this by handling interrupts only when the driver explicitly enables
    them and so it's guaranteed that the interrupt registers return a valid
    value.
    
    Note that this issue existed even before the above commit, since during
    runtime suspend/resume we never unregistered the handler.
    
    v2:
    - clarify the purpose of smp_mb() vs. synchronize_irq() in the
      code comment (Chris)
    
    v3:
    - no need for an explicit smp_mb(), we can assume that synchronize_irq()
      and the mmio read/writes in the install hooks provide for this (Daniel)
    - remove code comment as the remaining synchronize_irq() is self
      explanatory (Daniel)
    
    v4:
    - drm_irq_uninstall() implies synchronize_irq(), so no need to call it
      explicitly (Daniel)
    
    Reference: https://lkml.org/lkml/2015/2/11/205Reported-and-bisected-by: NKlaus Ethgen <Klaus@Ethgen.ch>
    Cc: stable@vger.kernel.org
    Signed-off-by: NImre Deak <imre.deak@intel.com>
    Reviewed-by: NDaniel Vetter <daniel.vetter@ffwll.ch>
    Signed-off-by: NJani Nikula <jani.nikula@intel.com>
    2dd2a883
i915_irq.c 127.9 KB