[Intel-gfx] [PATCH 2/6] drm/i915: Don't wait for Punit after each freq change on VLV

[ville.syrjala at linux.intel.com]

From: Ville Syrjälä <ville.syrjala at linux.intel.com>

It seems that even though Punit reports the frequency change to have
been completed, it still reports the old frequency in the status
register for some time.

So rather than polling for Punit to complete the frequency change after
each request, poll before. This gets rid of the spurious "Punit overrode
GPU freq" messages.

This also lets us continue working while Punit is performing the actual
frequency change. As a result, openarena demo088-test1 timedemo average
fps is increased by ~5 fps, and the slowest frame duration is reduced
by ~25%.

The sysfs cur_freq file always reads the current frequency from Punit
anyway, so having rps.cur_delay be slightly off at times doesn't matter.

Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
---
 drivers/gpu/drm/i915/intel_pm.c | 53 +++++++++++++++++++++++++++--------------
 1 file changed, 35 insertions(+), 18 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
index 48a3162..6dbcad7 100644
--- a/drivers/gpu/drm/i915/intel_pm.c
+++ b/drivers/gpu/drm/i915/intel_pm.c
@@ -3066,17 +3066,49 @@ void gen6_set_rps(struct drm_device *dev, u8 val)
 	trace_intel_gpu_freq_change(val * 50);
 }
 
+/*
+ * Wait until the previous freq change has completed,
+ * or the timeout elapsed, and then update our notion
+ * of the current GPU frequency.
+ */
+static void vlv_update_rps_cur_delay(struct drm_i915_private *dev_priv)
+{
+	unsigned long timeout = jiffies + msecs_to_jiffies(10);
+	u32 pval;
+
+	WARN_ON(!mutex_is_locked(&dev_priv->rps.hw_lock));
+
+	do {
+		pval = vlv_punit_read(dev_priv, PUNIT_REG_GPU_FREQ_STS);
+		if (time_after(jiffies, timeout)) {
+			DRM_DEBUG_DRIVER("timed out waiting for Punit\n");
+			break;
+		}
+		udelay(10);
+	} while (pval & 1);
+
+	pval >>= 8;
+
+	if (pval != dev_priv->rps.cur_delay)
+		DRM_DEBUG_DRIVER("Punit overrode GPU freq: %d MHz (%u) requested, but got %d Mhz (%u)\n",
+				 vlv_gpu_freq(dev_priv->mem_freq, dev_priv->rps.cur_delay),
+				 dev_priv->rps.cur_delay,
+				 vlv_gpu_freq(dev_priv->mem_freq, pval), pval);
+
+	dev_priv->rps.cur_delay = pval;
+}
+
 void valleyview_set_rps(struct drm_device *dev, u8 val)
 {
 	struct drm_i915_private *dev_priv = dev->dev_private;
-	unsigned long timeout = jiffies + msecs_to_jiffies(10);
 	u32 limits = gen6_rps_limits(dev_priv, &val);
-	u32 pval;
 
 	WARN_ON(!mutex_is_locked(&dev_priv->rps.hw_lock));
 	WARN_ON(val > dev_priv->rps.max_delay);
 	WARN_ON(val < dev_priv->rps.min_delay);
 
+	vlv_update_rps_cur_delay(dev_priv);
+
 	DRM_DEBUG_DRIVER("GPU freq request from %d MHz (%u) to %d MHz (%u)\n",
 			 vlv_gpu_freq(dev_priv->mem_freq,
 				      dev_priv->rps.cur_delay),
@@ -3088,27 +3120,12 @@ void valleyview_set_rps(struct drm_device *dev, u8 val)
 
 	vlv_punit_write(dev_priv, PUNIT_REG_GPU_FREQ_REQ, val);
 
-	do {
-		pval = vlv_punit_read(dev_priv, PUNIT_REG_GPU_FREQ_STS);
-		if (time_after(jiffies, timeout)) {
-			DRM_DEBUG_DRIVER("timed out waiting for Punit\n");
-			break;
-		}
-		udelay(10);
-	} while (pval & 1);
-
-	pval = vlv_punit_read(dev_priv, PUNIT_REG_GPU_FREQ_STS);
-	if ((pval >> 8) != val)
-		DRM_DEBUG_DRIVER("Punit overrode GPU freq: %d MHz (%u) requested, but got %d Mhz (%u)\n",
-				 vlv_gpu_freq(dev_priv->mem_freq, val), val,
-				 vlv_gpu_freq(dev_priv->mem_freq, pval >> 8), pval >> 8);
-
 	/* Make sure we continue to get interrupts
 	 * until we hit the minimum or maximum frequencies.
 	 */
 	I915_WRITE(GEN6_RP_INTERRUPT_LIMITS, limits);
 
-	dev_priv->rps.cur_delay = pval >> 8;
+	dev_priv->rps.cur_delay = val;
 
 	trace_intel_gpu_freq_change(vlv_gpu_freq(dev_priv->mem_freq, val));
 }
-- 
1.8.1.5