drm/i915: make enable/disable_gt_powersave locking consistent

The enable functions grabbed dev->struct_mutex themselves, whereas
the disable functions expected dev->struct_mutex to be held by the
caller. Move the locking out to the (currently only) callsite of
intel_enable_gt_powersave to make this more consistent.

Originally this was prep work for future patches, but I've chased down
a totally wrong alley. Still, I think this is a sensible
clarification.

Reviewed-by: Eugeni Dodonov <eugeni.dodonov@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/intel_display.c

@@ -7174,7 +7174,9 @@ void intel_modeset_init_hw(struct drm_device *dev)
 {
 	intel_init_clock_gating(dev);
 
+	mutex_lock(&dev->struct_mutex);
 	intel_enable_gt_powersave(dev);
+	mutex_unlock(&dev->struct_mutex);
 
 	if (IS_IVYBRIDGE(dev))
 		ivb_pch_pwm_override(dev);

drivers/gpu/drm/i915/intel_pm.c

@@ -2349,8 +2349,9 @@ int intel_enable_rc6(const struct drm_device *dev)
 	return (INTEL_RC6_ENABLE | INTEL_RC6p_ENABLE);
 }
 
-static void gen6_enable_rps(struct drm_i915_private *dev_priv)
+static void gen6_enable_rps(struct drm_device *dev)
 {
+	struct drm_i915_private *dev_priv = dev->dev_private;
 	struct intel_ring_buffer *ring;
 	u32 rp_state_cap;
 	u32 gt_perf_status;
@@ -2359,14 +2360,15 @@ static void gen6_enable_rps(struct drm_i915_private *dev_priv)
 	int rc6_mode;
 	int i;
 
+	WARN_ON(!mutex_is_locked(&dev->struct_mutex));
+
 	/* Here begins a magic sequence of register writes to enable
 	 * auto-downclocking.
 	 *
 	 * Perhaps there might be some value in exposing these to
 	 * userspace...
 	 */
 	I915_WRITE(GEN6_RC_STATE, 0);
-	mutex_lock(&dev_priv->dev->struct_mutex);
 
 	/* Clear the DBG now so we don't confuse earlier errors */
 	if ((gtfifodbg = I915_READ(GTFIFODBG))) {
@@ -2491,15 +2493,17 @@ static void gen6_enable_rps(struct drm_i915_private *dev_priv)
 	I915_WRITE(GEN6_PMINTRMSK, 0);
 
 	gen6_gt_force_wake_put(dev_priv);
-	mutex_unlock(&dev_priv->dev->struct_mutex);
 }
 
-static void gen6_update_ring_freq(struct drm_i915_private *dev_priv)
+static void gen6_update_ring_freq(struct drm_device *dev)
 {
+	struct drm_i915_private *dev_priv = dev->dev_private;
 	int min_freq = 15;
 	int gpu_freq, ia_freq, max_ia_freq;
 	int scaling_factor = 180;
 
+	WARN_ON(!mutex_is_locked(&dev->struct_mutex));
+
 	max_ia_freq = cpufreq_quick_get_max(0);
 	/*
 	 * Default to measured freq if none found, PCU will ensure we don't go
@@ -2511,8 +2515,6 @@ static void gen6_update_ring_freq(struct drm_i915_private *dev_priv)
 	/* Convert from kHz to MHz */
 	max_ia_freq /= 1000;
 
-	mutex_lock(&dev_priv->dev->struct_mutex);
-
 	/*
 	 * For each potential GPU frequency, load a ring frequency we'd like
 	 * to use for memory access.  We do this by specifying the IA frequency
@@ -2543,8 +2545,6 @@ static void gen6_update_ring_freq(struct drm_i915_private *dev_priv)
 			continue;
 		}
 	}
-
-	mutex_unlock(&dev_priv->dev->struct_mutex);
 }
 
 static void ironlake_teardown_rc6(struct drm_device *dev)
@@ -2615,12 +2615,11 @@ void ironlake_enable_rc6(struct drm_device *dev)
 	if (!intel_enable_rc6(dev))
 		return;
 
-	mutex_lock(&dev->struct_mutex);
+	WARN_ON(!mutex_is_locked(&dev->struct_mutex));
+
 	ret = ironlake_setup_rc6(dev);
-	if (ret) {
-		mutex_unlock(&dev->struct_mutex);
+	if (ret)
 		return;
-	}
 
 	/*
 	 * GPU can automatically power down the render unit if given a page
@@ -2629,7 +2628,6 @@ void ironlake_enable_rc6(struct drm_device *dev)
 	ret = intel_ring_begin(ring, 6);
 	if (ret) {
 		ironlake_teardown_rc6(dev);
-		mutex_unlock(&dev->struct_mutex);
 		return;
 	}
 
@@ -2654,13 +2652,11 @@ void ironlake_enable_rc6(struct drm_device *dev)
 	if (ret) {
 		DRM_ERROR("failed to enable ironlake power power savings\n");
 		ironlake_teardown_rc6(dev);
-		mutex_unlock(&dev->struct_mutex);
 		return;
 	}
 
 	I915_WRITE(PWRCTXA, dev_priv->pwrctx->gtt_offset | PWRCTX_EN);
 	I915_WRITE(RSTDBYCTL, I915_READ(RSTDBYCTL) & ~RCX_SW_EXIT);
-	mutex_unlock(&dev->struct_mutex);
 }
 
 static unsigned long intel_pxfreq(u32 vidfreq)
@@ -3237,17 +3233,15 @@ void intel_disable_gt_powersave(struct drm_device *dev)
 
 void intel_enable_gt_powersave(struct drm_device *dev)
 {
-	struct drm_i915_private *dev_priv = dev->dev_private;
-
 	if (IS_IRONLAKE_M(dev)) {
 		ironlake_enable_drps(dev);
 		ironlake_enable_rc6(dev);
 		intel_init_emon(dev);
 	}
 
 	if ((IS_GEN6(dev) || IS_GEN7(dev)) && !IS_VALLEYVIEW(dev)) {
-		gen6_enable_rps(dev_priv);
-		gen6_update_ring_freq(dev_priv);
+		gen6_enable_rps(dev);
+		gen6_update_ring_freq(dev);
 	}
 }