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: 773ea9a80132 ("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.uk
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>

diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
index aef0b105eb58bd8f04c9f60440583089bb82afbd..f9591b99d8ca05962f68e23b1316580d94fd742f 100644 (file)
--- 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);
 }