From: Chris Wilson <chris@chris-wilson.co.uk>
Date: Fri, 2 Feb 2018 14:54:55 +0000
Subject: drm/i915/execlists: Flush GTIIR on clearing CS interrupts during reset
Git-commit: 274de876065a34ca1ff093bfacb62e440a4491be
Patch-mainline: v4.17-rc1
References: FATE#326289 FATE#326079 FATE#326049 FATE#322398 FATE#326166

Be paranoid and flush the GTIIR after clearing the CS interrupt to be
sure it has taken before we re-enable the interrupt handler. We still
see early interrupts following reset, the tasklet handling the mmio read
before it has been written by the CS. This hopefully reduces the
frequency to 0...

References: https://bugs.freedesktop.org/show_bug.cgi?id=104262
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Cc: Michel Thierry <michel.thierry@intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Acked-by: Michel Thierry <michel.thierry@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180202145455.29876-1-chris@chris-wilson.co.uk

Acked-by: Petr Tesarik <ptesarik@suse.com>
---
 drivers/gpu/drm/i915/intel_lrc.c |   13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

--- a/drivers/gpu/drm/i915/intel_lrc.c
+++ b/drivers/gpu/drm/i915/intel_lrc.c
@@ -1532,6 +1532,7 @@ static int gen9_init_render_ring(struct
 static void reset_irq(struct intel_engine_cs *engine)
 {
 	struct drm_i915_private *dev_priv = engine->i915;
+	int i;
 
 	/*
 	 * Clear any pending interrupt state.
@@ -1540,10 +1541,14 @@ static void reset_irq(struct intel_engin
 	 * buffered, and if we only reset it once there may still be
 	 * an interrupt pending.
 	 */
-	I915_WRITE(GEN8_GT_IIR(gtiir[engine->id]),
-		   GT_CONTEXT_SWITCH_INTERRUPT << engine->irq_shift);
-	I915_WRITE(GEN8_GT_IIR(gtiir[engine->id]),
-		   GT_CONTEXT_SWITCH_INTERRUPT << engine->irq_shift);
+	for (i = 0; i < 2; i++) {
+		I915_WRITE(GEN8_GT_IIR(gtiir[engine->id]),
+			   GT_CONTEXT_SWITCH_INTERRUPT << engine->irq_shift);
+		POSTING_READ(GEN8_GT_IIR(gtiir[engine->id]));
+	}
+	GEM_BUG_ON(I915_READ(GEN8_GT_IIR(gtiir[engine->id])) &
+		   (GT_CONTEXT_SWITCH_INTERRUPT << engine->irq_shift));
+
 	clear_bit(ENGINE_IRQ_EXECLIST, &engine->irq_posted);
 }