drm/i915/gen6: Flush RING_IMR changes before changing the global GT IMR
authorChris Wilson <chris@chris-wilson.co.uk>
Wed, 2 Jan 2019 16:35:24 +0000 (16:35 +0000)
committerChris Wilson <chris@chris-wilson.co.uk>
Thu, 3 Jan 2019 10:40:28 +0000 (10:40 +0000)
commit476af9c2606354f14272297cea8b98afcb94cd8f
tree20c5456aaeef8007c4c31132aa51cdc9c20fb3f2
parent122503683169b21d9cdb90380a20caad7ba994b6
drm/i915/gen6: Flush RING_IMR changes before changing the global GT IMR

On Baytail, notably, we can still detect missed interrupt syndrome
(where we never spot a completed request). In this case, it can be
alleviated by always keeping the interrupt unmasked, implying that the
interrupt is being lost in the window after modifying the IMR. (This is
the reason we still have the posting reads on enable_irq, if we remove
them we miss interrupts!) Having narrowed the issue down to the IMR,
rather than keeping it always enabled, applying the usual posting
read/flush of the RING_IMR before unmasking the GT IMR also seems to
prevent the missed interrupt. So be it.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Acked-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190102163524.19353-1-chris@chris-wilson.co.uk
drivers/gpu/drm/i915/intel_ringbuffer.c