drm/i915: Fix nesting of rps.mutex and struct_mutex during powersave init

During intel_gt_powersave_init() we take the RPS mutex to ensure that
all locking requirements are met as we talk to the punit, but we also
require the struct_mutex for allocating a slice of the global GTT for a
power context on Valleyview. struct_mutex must be the outer lock here,
as we nest rps.mutex inside later on.
Reported-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Fixes: 773ea9a8 ("drm/i915: Perform static RPS frequency setup before...")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: Mika Kuoppala <mika.kuoppala@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1470833904-29886-1-git-send-email-chris@chris-wilson.co.ukReviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>

drivers/gpu/drm/i915/intel_pm.c

@@ -5675,8 +5675,6 @@ static void valleyview_setup_pctx(struct drm_i915_private *dev_priv)
 	u32 pcbr;
 	int pctx_size = 24*1024;
 
-	mutex_lock(&dev_priv->drm.struct_mutex);
-
 	pcbr = I915_READ(VLV_PCBR);
 	if (pcbr) {
 		/* BIOS set it up already, grab the pre-alloc'd space */
@@ -5712,7 +5710,6 @@ static void valleyview_setup_pctx(struct drm_i915_private *dev_priv)
 out:
 	DRM_DEBUG_DRIVER("PCBR: 0x%08x\n", I915_READ(VLV_PCBR));
 	dev_priv->vlv_pctx = pctx;
-	mutex_unlock(&dev_priv->drm.struct_mutex);
 }
 
 static void valleyview_cleanup_pctx(struct drm_i915_private *dev_priv)
@@ -6488,6 +6485,7 @@ void intel_init_gt_powersave(struct drm_i915_private *dev_priv)
 		intel_runtime_pm_get(dev_priv);
 	}
 
+	mutex_lock(&dev_priv->drm.struct_mutex);
 	mutex_lock(&dev_priv->rps.hw_lock);
 
 	/* Initialize RPS limits (for userspace) */
@@ -6529,6 +6527,7 @@ void intel_init_gt_powersave(struct drm_i915_private *dev_priv)
 	dev_priv->rps.boost_freq = dev_priv->rps.max_freq;
 
 	mutex_unlock(&dev_priv->rps.hw_lock);
+	mutex_unlock(&dev_priv->drm.struct_mutex);
 
 	intel_autoenable_gt_powersave(dev_priv);
 }