drm/i915: Relax RPS contraints to allows setting minfreq on idle

When we idle, we set the GPU frequency to the hardware minimum (not user
minimum). We introduce a new variable to distinguish between the
different roles, and to allow easy tuning of the idle frequency without
impacting over aspects of RPS. Setting the minimum frequency should be a
safety blanket as the pcu on the GPU should be power gating itself
anyway. However, in order for us to do set the absolute minimum
frequency, we need to relax a few of our assertions that we do not
exceed the user limits.

v2: Add idle_freq
v3: Init idle_freq for vlv and add a bunch of WARNs

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Deepak S <deepak.s@linux.intel.com>
Reviewed-by: Deepak S<deepak.s@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_debugfs.c

@@ -1200,6 +1200,9 @@ static int i915_frequency_info(struct seq_file *m, void *unused)
 
 		seq_printf(m, "Max overclocked frequency: %dMHz\n",
 			   intel_gpu_freq(dev_priv, dev_priv->rps.max_freq));
+
+		seq_printf(m, "Idle freq: %d MHz\n",
+			   intel_gpu_freq(dev_priv, dev_priv->rps.idle_freq));
 	} else if (IS_VALLEYVIEW(dev)) {
 		u32 freq_sts;
 
@@ -1214,6 +1217,9 @@ static int i915_frequency_info(struct seq_file *m, void *unused)
 		seq_printf(m, "min GPU freq: %d MHz\n",
 			   intel_gpu_freq(dev_priv, dev_priv->rps.min_freq));
 
+		seq_printf(m, "idle GPU freq: %d MHz\n",
+			   intel_gpu_freq(dev_priv, dev_priv->rps.idle_freq));
+
 		seq_printf(m,
 			   "efficient (RPe) frequency: %d MHz\n",
 			   intel_gpu_freq(dev_priv, dev_priv->rps.efficient_freq));

drivers/gpu/drm/i915/i915_drv.h

@@ -1025,6 +1025,7 @@ struct intel_gen6_power_mgmt {
 	u8 max_freq_softlimit;	/* Max frequency permitted by the driver */
 	u8 max_freq;		/* Maximum frequency, RP0 if not overclocking */
 	u8 min_freq;		/* AKA RPn. Minimum frequency */
+	u8 idle_freq;		/* Frequency to request when we are idle */
 	u8 efficient_freq;	/* AKA RPe. Pre-determined balanced frequency */
 	u8 rp1_freq;		/* "less than" RP0 power/freqency */
 	u8 rp0_freq;		/* Non-overclocked max frequency. */

drivers/gpu/drm/i915/intel_pm.c

@@ -3855,9 +3855,9 @@ static void gen6_set_rps_thresholds(struct drm_i915_private *dev_priv, u8 val)
 		break;
 	}
 	/* Max/min bins are special */
-	if (val == dev_priv->rps.min_freq_softlimit)
+	if (val <= dev_priv->rps.min_freq_softlimit)
 		new_power = LOW_POWER;
-	if (val == dev_priv->rps.max_freq_softlimit)
+	if (val >= dev_priv->rps.max_freq_softlimit)
 		new_power = HIGH_POWER;
 	if (new_power == dev_priv->rps.power)
 		return;
@@ -3940,8 +3940,8 @@ static void gen6_set_rps(struct drm_device *dev, u8 val)
 	struct drm_i915_private *dev_priv = dev->dev_private;
 
 	WARN_ON(!mutex_is_locked(&dev_priv->rps.hw_lock));
-	WARN_ON(val > dev_priv->rps.max_freq_softlimit);
-	WARN_ON(val < dev_priv->rps.min_freq_softlimit);
+	WARN_ON(val > dev_priv->rps.max_freq);
+	WARN_ON(val < dev_priv->rps.min_freq);
 
 	/* min/max delay may still have been modified so be sure to
 	 * write the limits value.
@@ -3979,8 +3979,8 @@ static void valleyview_set_rps(struct drm_device *dev, u8 val)
 	struct drm_i915_private *dev_priv = dev->dev_private;
 
 	WARN_ON(!mutex_is_locked(&dev_priv->rps.hw_lock));
-	WARN_ON(val > dev_priv->rps.max_freq_softlimit);
-	WARN_ON(val < dev_priv->rps.min_freq_softlimit);
+	WARN_ON(val > dev_priv->rps.max_freq);
+	WARN_ON(val < dev_priv->rps.min_freq);
 
 	if (WARN_ONCE(IS_CHERRYVIEW(dev) && (val & 1),
 		      "Odd GPU freq value\n"))
@@ -4007,18 +4007,19 @@ static void valleyview_set_rps(struct drm_device *dev, u8 val)
 static void vlv_set_rps_idle(struct drm_i915_private *dev_priv)
 {
 	struct drm_device *dev = dev_priv->dev;
+	u32 val = dev_priv->rps.idle_freq;
 
 	/* CHV and latest VLV don't need to force the gfx clock */
 	if (IS_CHERRYVIEW(dev) || dev->pdev->revision >= 0xd) {
-		valleyview_set_rps(dev_priv->dev, dev_priv->rps.min_freq_softlimit);
+		valleyview_set_rps(dev_priv->dev, val);
 		return;
 	}
 
 	/*
 	 * When we are idle.  Drop to min voltage state.
 	 */
 
-	if (dev_priv->rps.cur_freq <= dev_priv->rps.min_freq_softlimit)
+	if (dev_priv->rps.cur_freq <= val)
 		return;
 
 	/* Mask turbo interrupt so that they will not come in between */
@@ -4027,19 +4028,17 @@ static void vlv_set_rps_idle(struct drm_i915_private *dev_priv)
 
 	vlv_force_gfx_clock(dev_priv, true);
 
-	dev_priv->rps.cur_freq = dev_priv->rps.min_freq_softlimit;
+	dev_priv->rps.cur_freq = val;
 
-	vlv_punit_write(dev_priv, PUNIT_REG_GPU_FREQ_REQ,
-					dev_priv->rps.min_freq_softlimit);
+	vlv_punit_write(dev_priv, PUNIT_REG_GPU_FREQ_REQ, val);
 
 	if (wait_for(((vlv_punit_read(dev_priv, PUNIT_REG_GPU_FREQ_STS))
 				& GENFREQSTATUS) == 0, 100))
 		DRM_ERROR("timed out waiting for Punit\n");
 
 	vlv_force_gfx_clock(dev_priv, false);
 
-	I915_WRITE(GEN6_PMINTRMSK,
-		   gen6_rps_pm_mask(dev_priv, dev_priv->rps.cur_freq));
+	I915_WRITE(GEN6_PMINTRMSK, gen6_rps_pm_mask(dev_priv, val));
 }
 
 void gen6_rps_idle(struct drm_i915_private *dev_priv)
@@ -4051,7 +4050,7 @@ void gen6_rps_idle(struct drm_i915_private *dev_priv)
 		if (IS_VALLEYVIEW(dev))
 			vlv_set_rps_idle(dev_priv);
 		else
-			gen6_set_rps(dev_priv->dev, dev_priv->rps.min_freq_softlimit);
+			gen6_set_rps(dev_priv->dev, dev_priv->rps.idle_freq);
 		dev_priv->rps.last_adj = 0;
 	}
 	mutex_unlock(&dev_priv->rps.hw_lock);
@@ -4209,6 +4208,8 @@ static void gen6_init_rps_frequencies(struct drm_device *dev)
 					dev_priv->rps.max_freq);
 	}
 
+	dev_priv->rps.idle_freq = dev_priv->rps.min_freq;
+
 	/* Preserve min/max settings in case of re-init */
 	if (dev_priv->rps.max_freq_softlimit == 0)
 		dev_priv->rps.max_freq_softlimit = dev_priv->rps.max_freq;
@@ -4375,7 +4376,7 @@ static void gen8_enable_rps(struct drm_device *dev)
 	/* 6: Ring frequency + overclocking (our driver does this later */
 
 	dev_priv->rps.power = HIGH_POWER; /* force a reset */
-	gen6_set_rps(dev_priv->dev, dev_priv->rps.min_freq_softlimit);
+	gen6_set_rps(dev_priv->dev, dev_priv->rps.idle_freq);
 
 	intel_uncore_forcewake_put(dev_priv, FORCEWAKE_ALL);
 }
@@ -4469,7 +4470,7 @@ static void gen6_enable_rps(struct drm_device *dev)
 	}
 
 	dev_priv->rps.power = HIGH_POWER; /* force a reset */
-	gen6_set_rps(dev_priv->dev, dev_priv->rps.min_freq_softlimit);
+	gen6_set_rps(dev_priv->dev, dev_priv->rps.idle_freq);
 
 	rc6vids = 0;
 	ret = sandybridge_pcode_read(dev_priv, GEN6_PCODE_READ_RC6VIDS, &rc6vids);
@@ -4834,6 +4835,8 @@ static void valleyview_init_gt_powersave(struct drm_device *dev)
 			 intel_gpu_freq(dev_priv, dev_priv->rps.min_freq),
 			 dev_priv->rps.min_freq);
 
+	dev_priv->rps.idle_freq = dev_priv->rps.min_freq;
+
 	/* Preserve min/max settings in case of re-init */
 	if (dev_priv->rps.max_freq_softlimit == 0)
 		dev_priv->rps.max_freq_softlimit = dev_priv->rps.max_freq;
@@ -4909,6 +4912,8 @@ static void cherryview_init_gt_powersave(struct drm_device *dev)
 		   dev_priv->rps.min_freq) & 1,
 		  "Odd GPU freq values\n");
 
+	dev_priv->rps.idle_freq = dev_priv->rps.min_freq;
+
 	/* Preserve min/max settings in case of re-init */
 	if (dev_priv->rps.max_freq_softlimit == 0)
 		dev_priv->rps.max_freq_softlimit = dev_priv->rps.max_freq;
@@ -5686,6 +5691,13 @@ static void intel_gen6_powersave_work(struct work_struct *work)
 		gen6_enable_rps(dev);
 		__gen6_update_ring_freq(dev);
 	}
+
+	WARN_ON(dev_priv->rps.max_freq < dev_priv->rps.min_freq);
+	WARN_ON(dev_priv->rps.idle_freq > dev_priv->rps.max_freq);
+
+	WARN_ON(dev_priv->rps.efficient_freq < dev_priv->rps.min_freq);
+	WARN_ON(dev_priv->rps.efficient_freq > dev_priv->rps.max_freq);
+
 	dev_priv->rps.enabled = true;
 
 	gen6_enable_rps_interrupts(dev);