From fa7545a4ae8c1a0640a294db4f8b6bab8a68dcd0 Mon Sep 17 00:00:00 2001 From: Dave Gordon Date: Fri, 24 Jun 2016 15:57:57 +0100 Subject: [PATCH] drm/i915/guc: don't ever forward VBlank to the GuC If a context waiting for VBlank were switched out, switching in the next context and generating a CSB event in the process, then the GuC would have to put the context back in the queue, and then observe the subsequent VBlank interrupt so that it could resubmit the suspended context. However, we always set the CTX_CTRL_INHIBIT_SYN_CTX_SWITCH bit in the RING_CONTEXT_CONTROL register, so this case cannot occur. Furthermore we don't use the GuC's internal scheduler or allow it to auto-resubmit workloads. Consequently, the GuC doesn't need to see VBlanks, and by sending them to it we may be waking it up unnecessarily, which might reduce RC6 residency and increase power consumption. So this patch removes the setting of the GFC_FORWARD_VBLANK field from the code that diverts interrupts towards the GuC. (The code to direct interrupts to the host, OTOH, continues to explicitly set the field to "never send VBlanks to the GuC".) v3: Remove the line of code completely (original set the field to ALWAYS forward, v1 changed it to CONDITIONAL forwarding, v2 explicitly set it to NEVER, v3 just doesn't touch it at all, as we know it's already set to NEVER). Signed-off-by: Dave Gordon Reviewed-by: Daniel Vetter (previous version) Reviewed-by: Tvrtko Ursulin Signed-off-by: Tvrtko Ursulin Link: http://patchwork.freedesktop.org/patch/msgid/1466780277-23435-1-git-send-email-david.s.gordon@intel.com --- drivers/gpu/drm/i915/intel_guc_loader.c | 7 +++---- 1 file changed, 3 insertions(+), 4 deletions(-) diff --git a/drivers/gpu/drm/i915/intel_guc_loader.c b/drivers/gpu/drm/i915/intel_guc_loader.c index 8fe96a2d989e..4f6311a91a7e 100644 --- a/drivers/gpu/drm/i915/intel_guc_loader.c +++ b/drivers/gpu/drm/i915/intel_guc_loader.c @@ -87,7 +87,7 @@ static void direct_interrupts_to_host(struct drm_i915_private *dev_priv) struct intel_engine_cs *engine; int irqs; - /* tell all command streamers NOT to forward interrupts and vblank to GuC */ + /* tell all command streamers NOT to forward interrupts or vblank to GuC */ irqs = _MASKED_FIELD(GFX_FORWARD_VBLANK_MASK, GFX_FORWARD_VBLANK_NEVER); irqs |= _MASKED_BIT_DISABLE(GFX_INTERRUPT_STEERING); for_each_engine(engine, dev_priv) @@ -105,9 +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); - irqs |= _MASKED_BIT_ENABLE(GFX_INTERRUPT_STEERING); + /* tell all command streamers to forward interrupts (but not vblank) to GuC */ + irqs = _MASKED_BIT_ENABLE(GFX_INTERRUPT_STEERING); for_each_engine(engine, dev_priv) I915_WRITE(RING_MODE_GEN7(engine), irqs); -- 2.20.1