Re: [Intel-gfx] [PATCH] drm/i915: vlv: fix IRQ masking when uninstalling interrupts

[Jani Nikula <jani.nikula@linux.intel.com>]

On Wed, 10 Dec 2014, Ville Syrjälä <ville.syrjala@linux.intel.com> 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@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>

Pushed to drm-intel-next-fixes, thanks for the patch and review.

BR,
Jani.


>
>> ---
>>  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;
>>  }
>>  
>>  static void valleyview_irq_uninstall(struct drm_device *dev)
>> -- 
>> 1.8.4
>> 
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>> http://lists.freedesktop.org/mailman/listinfo/intel-gfx
>
> -- 
> Ville Syrjälä
> Intel OTC
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-- 
Jani Nikula, Intel Open Source Technology Center