From e4fc69f24b07eca44dba5dab94c574d8602eabb8 Mon Sep 17 00:00:00 2001 From: Chris Wilson Date: Sat, 5 Jan 2019 11:56:47 +0000 Subject: [PATCH] drm/i915/hsw: Flush RING_IMR changes before changing the global GT IMR (vecs) Haswell also requires the RING_IMR flush for its unique vebox setup to avoid losing interrupts, as per 476af9c26063 ("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. References: 476af9c26063 ("drm/i915/gen6: Flush RING_IMR changes before changing the global GT IMR") Signed-off-by: Chris Wilson Cc: Mika Kuoppala Reviewed-by: Mika Kuoppala Link: https://patchwork.freedesktop.org/patch/msgid/20190105115647.4970-1-chris@chris-wilson.co.uk --- drivers/gpu/drm/i915/intel_ringbuffer.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c index 3d5d6b908148..6e2661e86d18 100644 --- a/drivers/gpu/drm/i915/intel_ringbuffer.c +++ b/drivers/gpu/drm/i915/intel_ringbuffer.c @@ -996,6 +996,10 @@ hsw_vebox_irq_enable(struct intel_engine_cs *engine) struct drm_i915_private *dev_priv = engine->i915; I915_WRITE_IMR(engine, ~engine->irq_enable_mask); + + /* Flush/delay to ensure the RING_IMR is active before the GT IMR */ + POSTING_READ_FW(RING_IMR(engine->mmio_base)); + gen6_unmask_pm_irq(dev_priv, engine->irq_enable_mask); } -- 2.30.2