[Intel-gfx] [PATCH] drm/i915: Fix nesting of rps.mutex and struct_mutex during powersave init

[Chris Wilson]

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 at linux.intel.com>
Fixes: 773ea9a80132 ("drm/i915: Perform static RPS frequency setup before...")
Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Ville Syrjälä <ville.syrjala at linux.intel.com>
Cc: Mika Kuoppala <mika.kuoppala at intel.com>
---
 drivers/gpu/drm/i915/intel_pm.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
index 1035eb5e52dd..20794804f3bb 100644
--- a/drivers/gpu/drm/i915/intel_pm.c
+++ b/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);
 }
-- 
2.8.1