drm/i915: fix ilk rc6 teardown locking

In the failure cases during rc6 initialization, both the power context
and render context may get !refcount without holding struct_mutex.
However, on rc6 disabling, the lock is held by the caller.

Rearranged the locking so that it's safe in both cases.

Signed-off-by: Ben Widawsky <ben@bwidawsk.net>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Keith Packard <keithp@keithp.com>
Signed-off-by: Keith Packard <keithp@keithp.com>

1 files changed, 8 insertions, 3 deletions

diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index bcef1c1e83fc..b6f593a6d970 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -6713,13 +6713,14 @@ intel_alloc_context_page(struct drm_device *dev)
         struct drm_i915_gem_object *ctx;
         int ret;
 
+        WARN_ON(!mutex_is_locked(&dev->struct_mutex));
+
         ctx = i915_gem_alloc_object(dev, 4096);
         if (!ctx) {
                 DRM_DEBUG("failed to alloc power context, RC6 disabled\n");
                 return NULL;
         }
 
-        mutex_lock(&dev->struct_mutex);
         ret = i915_gem_object_pin(ctx, 4096, true);
         if (ret) {
                 DRM_ERROR("failed to pin power context: %d\n", ret);
@@ -6731,7 +6732,6 @@ intel_alloc_context_page(struct drm_device *dev)
                 DRM_ERROR("failed to set-domain on power context: %d\n", ret);
                 goto err_unpin;
         }
-        mutex_unlock(&dev->struct_mutex);
 
         return ctx;
 
@@ -7295,9 +7295,12 @@ void ironlake_enable_rc6(struct drm_device *dev)
         if (!i915_enable_rc6)
                 return;
 
+        mutex_lock(&dev->struct_mutex);
         ret = ironlake_setup_rc6(dev);
-        if (ret)
+        if (ret) {
+                mutex_unlock(&dev->struct_mutex);
                 return;
+        }
 
         /*
          * GPU can automatically power down the render unit if given a page
@@ -7306,6 +7309,7 @@ void ironlake_enable_rc6(struct drm_device *dev)
         ret = BEGIN_LP_RING(6);
         if (ret) {
                 ironlake_teardown_rc6(dev);
+                mutex_unlock(&dev->struct_mutex);
                 return;
         }
 
@@ -7323,6 +7327,7 @@ void ironlake_enable_rc6(struct drm_device *dev)
 
         I915_WRITE(PWRCTXA, dev_priv->pwrctx->gtt_offset | PWRCTX_EN);
         I915_WRITE(RSTDBYCTL, I915_READ(RSTDBYCTL) & ~RCX_SW_EXIT);
+        mutex_unlock(&dev->struct_mutex);
 }