[Intel-gfx] [PATCH] drm/i915: make sure GPU freq drops to minimum after entering RC6 v3

[Jesse Barnes]

On VLV, the Punit doesn't automatically drop the GPU to it's minimum
voltage level when entering RC6, so we arm a timer to do it for us from
the RPS interrupt handler.  It'll generally only fire when we go idle
(or if for some reason there's a long delay between RPS interrupts), but
won't be re-armed again until the next RPS event, so shouldn't affect
power consumption after we go idle and it triggers.

v2: use delayed work instead of timer + work queue combo (Ville)
v3: fix up delayed work cancel (must be outside lock) (Daniel)
    fix up delayed work handling func for delayed work (Jesse)

Signed-off-by: Jesse Barnes <jbarnes at virtuousgeek.org>
---
 drivers/gpu/drm/i915/i915_drv.h |    2 ++
 drivers/gpu/drm/i915/i915_irq.c |   11 +++++++++++
 drivers/gpu/drm/i915/intel_pm.c |   22 ++++++++++++++++++++++
 3 files changed, 35 insertions(+)

diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 2557fc7..f563f25 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -660,6 +660,7 @@ struct i915_suspend_saved_registers {
 
 struct intel_gen6_power_mgmt {
 	struct work_struct work;
+	struct delayed_work vlv_work;
 	u32 pm_iir;
 	/* lock - irqsave spinlock that protectects the work_struct and
 	 * pm_iir. */
@@ -670,6 +671,7 @@ struct intel_gen6_power_mgmt {
 	u8 cur_delay;
 	u8 min_delay;
 	u8 max_delay;
+	u8 rpe_delay;
 	u8 hw_max;
 
 	struct delayed_work delayed_resume_work;
diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c
index 932e7f8..af385e2 100644
--- a/drivers/gpu/drm/i915/i915_irq.c
+++ b/drivers/gpu/drm/i915/i915_irq.c
@@ -488,6 +488,17 @@ static void gen6_pm_rps_work(struct work_struct *work)
 			gen6_set_rps(dev_priv->dev, new_delay);
 	}
 
+	if (IS_VALLEYVIEW(dev_priv->dev)) {
+		/*
+		 * On VLV, when we enter RC6 we may not be at the minimum
+		 * voltage level, so arm a timer to check.  It should only
+		 * fire when there's activity or once after we've entered
+		 * RC6, and then won't be re-armed until the next RPS interrupt.
+		 */
+		mod_delayed_work(dev_priv->wq, &dev_priv->rps.vlv_work,
+				 jiffies + msecs_to_jiffies(100));
+	}
+
 	mutex_unlock(&dev_priv->rps.hw_lock);
 }
 
diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
index 2557926..c106187 100644
--- a/drivers/gpu/drm/i915/intel_pm.c
+++ b/drivers/gpu/drm/i915/intel_pm.c
@@ -2822,6 +2822,23 @@ int valleyview_rps_min_freq(struct drm_i915_private *dev_priv)
 	return val & 0xff;
 }
 
+static void vlv_rps_timer_work(struct work_struct *work)
+{
+	drm_i915_private_t *dev_priv = container_of(work, drm_i915_private_t,
+						    rps.vlv_work.work);
+
+	/*
+	 * Timer fired, we must be idle.  Drop to min voltage state.
+	 * Note: we use RPe here since it should match the
+	 * Vmin we were shooting for.  That should give us better
+	 * perf when we come back out of RC6 than if we used the
+	 * min freq available.
+	 */
+	mutex_lock(&dev_priv->rps.hw_lock);
+	valleyview_set_rps(dev_priv->dev, dev_priv->rps.rpe_delay);
+	mutex_unlock(&dev_priv->rps.hw_lock);
+}
+
 static void valleyview_enable_rps(struct drm_device *dev)
 {
 	struct drm_i915_private *dev_priv = dev->dev_private;
@@ -2886,6 +2903,7 @@ static void valleyview_enable_rps(struct drm_device *dev)
 	rpe = valleyview_rps_rpe_freq(dev_priv);
 	DRM_DEBUG_DRIVER("RPe GPU freq: %d\n",
 			 vlv_gpu_freq(dev_priv->mem_freq, rpe));
+	dev_priv->rps.rpe_delay = rpe;
 
 	val = valleyview_rps_min_freq(dev_priv);
 	DRM_DEBUG_DRIVER("min GPU freq: %d\n", vlv_gpu_freq(dev_priv->mem_freq,
@@ -2895,6 +2913,8 @@ static void valleyview_enable_rps(struct drm_device *dev)
 	DRM_DEBUG_DRIVER("setting GPU freq to %d\n",
 			 vlv_gpu_freq(dev_priv->mem_freq, rpe));
 
+	INIT_DELAYED_WORK(&dev_priv->rps.vlv_work, vlv_rps_timer_work);
+
 	valleyview_set_rps(dev_priv->dev, rpe);
 
 	/* requires MSI enabled */
@@ -3640,6 +3660,8 @@ void intel_disable_gt_powersave(struct drm_device *dev)
 		mutex_lock(&dev_priv->rps.hw_lock);
 		gen6_disable_rps(dev);
 		mutex_unlock(&dev_priv->rps.hw_lock);
+		if (IS_VALLEYVIEW(dev))
+			cancel_delayed_work_sync(&dev_priv->rps.vlv_work);
 	}
 }
 
-- 
1.7.10.4