[Intel-gfx] [PATCH 1/2] drm/i915: Unmask user interrupts writes into HWSP on snb/ivb/vlv/hsw

[Chris Wilson]

An oddity occurs on Sandybridge, Ivybridge and Haswell (and presumably
Valleyview) in that for the period following the GPU restart after a
reset, there are no GT interrupts received. From Ville's notes, bit 0 in
the HWSTAM corresponds to the render interrupt, and if we unmask it we
do see immediate resumption of GT interrupt delivery (via the master irq
handler) after the reset.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=107500
Fixes: c5498089463b ("drm/i915: Mask everything in ring HWSTAM on gen6+ in ringbuffer mode")
References: d420a50c21ef ("drm/i915: Clean up the HWSTAM mess")
Testcase: igt/gem_eio/reset-stress
Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Ville Syrjälä <ville.syrjala at linux.intel.com>
---
 drivers/gpu/drm/i915/intel_ringbuffer.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c
index 8003cef767ba..9b526b0f755a 100644
--- a/drivers/gpu/drm/i915/intel_ringbuffer.c
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
@@ -388,7 +388,7 @@ static void intel_ring_setup_status_page(struct intel_engine_cs *engine)
 	}
 
 	if (INTEL_GEN(dev_priv) >= 6)
-		I915_WRITE(RING_HWSTAM(engine->mmio_base), 0xffffffff);
+		I915_WRITE(RING_HWSTAM(engine->mmio_base), 0xfffffffe);
 
 	I915_WRITE(mmio, engine->status_page.ggtt_offset);
 	POSTING_READ(mmio);
-- 
2.18.0