[Intel-gfx] [PATCH 05/12] drm/i915: Clear VLV_IER around irq processing

[Chris Wilson]

On Wed, Apr 13, 2016 at 09:19:51PM +0300, ville.syrjala at linux.intel.com wrote:
> From: Ville Syrjälä <ville.syrjala at linux.intel.com>
> 
> On VLV/CHV the master interrupt enable bit only affects GT/PM
> interrupts. Display interrupts are not affected by the master
> irq control.
> 
> Also it seems that the CPU interrupt will only be generated when
> the combined result of all GT/PM/display interrupts has a 0->1
> edge. We already use the master interrupt enable bit to make sure
> GT/PM interrupt can generate such an edge if we don't end up clearing
> all IIR bits. We must do the same for display interrupts, and for
> that we can simply clear out VLV_IER, and restore after we've acked
> all the interrupts we are about to process.
> 
> So with both master interrupt enable and VLV_IER cleared out, we will
> guarantee that there will be a 0->1 edge if any IIR bits are still set
> at the end, and thus another CPU interrupt will be generated.
> 
> Cc: Chris Wilson <chris at chris-wilson.co.uk>
> Cc: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
> Fixes: 579de73b048a ("drm/i915: Exit cherryview_irq_handler() after one pass")
> Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>

Ville is very persuasive,
Reviewed-by: Chris Wilson <chris at chris-wilson.co.uk>

Other than wishing the extra POSTING_READ and reading known registers
away, the rest of the series is also
Reviewed-by: Chris Wilson <chris at chris-wilson.co.uk>
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre