[Intel-gfx] [PATCH] drm/i915/guc: don't ever forward VBlank to the GuC

[Dave Gordon]

If a context waiting for VBlank were switched out, the GuC would
have to receive the VBlank interrupt so that it could resubmit
the context. However, we don't use the GuC internal scheduler,
and we always set the CTX_CTRL_INHIBIT_SYN_CTX_SWITCH bit in the
RING_CONTEXT_CONTROL register, so this case cannot arise.

Consequently, the GuC doesn't need to see VBlanks, and we may be
waking it up unnecessarily by sending them. So let's not ...

Signed-off-by: Dave Gordon <david.s.gordon at intel.com>
---
 drivers/gpu/drm/i915/intel_guc_loader.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_guc_loader.c b/drivers/gpu/drm/i915/intel_guc_loader.c
index 8fe96a2..5d989d2 100644
--- a/drivers/gpu/drm/i915/intel_guc_loader.c
+++ b/drivers/gpu/drm/i915/intel_guc_loader.c
@@ -105,8 +105,8 @@ static void direct_interrupts_to_guc(struct drm_i915_private *dev_priv)
 	int irqs;
 	u32 tmp;
 
-	/* tell all command streamers to forward interrupts and vblank to GuC */
-	irqs = _MASKED_FIELD(GFX_FORWARD_VBLANK_MASK, GFX_FORWARD_VBLANK_ALWAYS);
+	/* tell all command streamers to forward interrupts (but not vblank) to GuC */
+	irqs = _MASKED_FIELD(GFX_FORWARD_VBLANK_MASK, GFX_FORWARD_VBLANK_NEVER);
 	irqs |= _MASKED_BIT_ENABLE(GFX_INTERRUPT_STEERING);
 	for_each_engine(engine, dev_priv)
 		I915_WRITE(RING_MODE_GEN7(engine), irqs);
-- 
1.9.1