[Intel-gfx] [PATCH] drm/i915: Mask PM/RPS interrupt generation based on activity

[Chris Wilson]

The speculation is that we can conserve more power by masking off
the interrupts at source (PMINTRMSK) rather than filtering them by the
up/down thresholds (RPINTLIM). We can select which events we know will
be active based on the current frequency versus our imposed range, i.e.
if at minimum, we know we will not want to generate any more
down-interrupts and vice versa.

v2: We only need the TIMEOUT when above min frequency.
v3: Tweak VLV at the same time

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Deepak S <deepak.s at linux.intel.com>
---
I see your point that I cannot remove PMINTRMSK from enable_interrupts
without tweaking VLV at the same time. I did consider making this 4
patches (factor out gen6_rps_pm_mask, tweak gen6+, tweak, vlv, remove it
from enable_interrupts) but decided that was just being silly and
squashed the two patches together instead.
---
 drivers/gpu/drm/i915/intel_pm.c | 41 +++++++++++++++++++++++++----------------
 1 file changed, 25 insertions(+), 16 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
index 154aa07d51a7..35a7b5b65883 100644
--- a/drivers/gpu/drm/i915/intel_pm.c
+++ b/drivers/gpu/drm/i915/intel_pm.c
@@ -3006,6 +3006,24 @@ static void gen6_set_rps_thresholds(struct drm_i915_private *dev_priv, u8 val)
 	dev_priv->rps.last_adj = 0;
 }
 
+static u32 gen6_rps_pm_mask(struct drm_i915_private *dev_priv, u8 val)
+{
+	u32 mask = 0;
+
+	if (val > dev_priv->rps.min_freq_softlimit)
+		mask |= GEN6_PM_RP_DOWN_THRESHOLD | GEN6_PM_RP_DOWN_TIMEOUT;
+	if (val < dev_priv->rps.max_freq_softlimit)
+		mask |= GEN6_PM_RP_UP_THRESHOLD;
+
+	/* IVB and SNB hard hangs on looping batchbuffer
+	 * if GEN6_PM_UP_EI_EXPIRED is masked.
+	 */
+	if (INTEL_INFO(dev_priv->dev)->gen <= 7 && !IS_HASWELL(dev_priv->dev))
+		mask |= GEN6_PM_RP_UP_EI_EXPIRED;
+
+	return ~mask;
+}
+
 /* gen6_set_rps is called to update the frequency request, but should also be
  * called when the range (min_delay and max_delay) is modified so that we can
  * update the GEN6_RP_INTERRUPT_LIMITS register accordingly. */
@@ -3037,6 +3055,7 @@ void gen6_set_rps(struct drm_device *dev, u8 val)
 	 * until we hit the minimum or maximum frequencies.
 	 */
 	I915_WRITE(GEN6_RP_INTERRUPT_LIMITS, gen6_rps_limits(dev_priv, val));
+	I915_WRITE(GEN6_PMINTRMSK, gen6_rps_pm_mask(dev_priv, val));
 
 	POSTING_READ(GEN6_RPNSWREQ);
 
@@ -3089,6 +3108,9 @@ static void vlv_set_rps_idle(struct drm_i915_private *dev_priv)
 	I915_WRITE(VLV_GTLC_SURVIVABILITY_REG,
 		I915_READ(VLV_GTLC_SURVIVABILITY_REG) &
 				~VLV_GFX_CLK_FORCE_ON_BIT);
+
+	I915_WRITE(GEN6_PMINTRMSK,
+		   gen6_rps_pm_mask(dev_priv, dev_priv->rps.cur_freq));
 }
 
 void gen6_rps_idle(struct drm_i915_private *dev_priv)
@@ -3134,13 +3156,12 @@ void valleyview_set_rps(struct drm_device *dev, u8 val)
 			 dev_priv->rps.cur_freq,
 			 vlv_gpu_freq(dev_priv, val), val);
 
-	if (val == dev_priv->rps.cur_freq)
-		return;
+	if (val != dev_priv->rps.cur_freq)
+		vlv_punit_write(dev_priv, PUNIT_REG_GPU_FREQ_REQ, val);
 
-	vlv_punit_write(dev_priv, PUNIT_REG_GPU_FREQ_REQ, val);
+	I915_WRITE(GEN6_PMINTRMSK, val);
 
 	dev_priv->rps.cur_freq = val;
-
 	trace_intel_gpu_freq_change(vlv_gpu_freq(dev_priv, val));
 }
 
@@ -3220,24 +3241,12 @@ int intel_enable_rc6(const struct drm_device *dev)
 static void gen6_enable_rps_interrupts(struct drm_device *dev)
 {
 	struct drm_i915_private *dev_priv = dev->dev_private;
-	u32 enabled_intrs;
 
 	spin_lock_irq(&dev_priv->irq_lock);
 	WARN_ON(dev_priv->rps.pm_iir);
 	snb_enable_pm_irq(dev_priv, dev_priv->pm_rps_events);
 	I915_WRITE(GEN6_PMIIR, dev_priv->pm_rps_events);
 	spin_unlock_irq(&dev_priv->irq_lock);
-
-	/* only unmask PM interrupts we need. Mask all others. */
-	enabled_intrs = dev_priv->pm_rps_events;
-
-	/* IVB and SNB hard hangs on looping batchbuffer
-	 * if GEN6_PM_UP_EI_EXPIRED is masked.
-	 */
-	if (INTEL_INFO(dev)->gen <= 7 && !IS_HASWELL(dev))
-		enabled_intrs |= GEN6_PM_RP_UP_EI_EXPIRED;
-
-	I915_WRITE(GEN6_PMINTRMSK, ~enabled_intrs);
 }
 
 static void gen8_enable_rps(struct drm_device *dev)
-- 
1.9.1