drm/i915: Fix struct mutex vs. RPS lock inversion

RPS lock must be taken before the struct_mutex to avoid
locking inversion. So stop grabbing it for the whole
powersave initialization and instead only take it during
the sections which need it.

Also, struct_mutex is not needed any more since dedicated
RPS lock was added in:

   commit 4fc688ce79772496503d22263d61b071a8fb596e
   Author: Jesse Barnes <jbarnes@virtuousgeek.org>
   Date:   Fri Nov 2 11:14:01 2012 -0700

       drm/i915: protect RPS/RC6 related accesses (including PCU) with a new mutex

Based on prototype patch by Chris Wilson and a subsequent
mailing list discussion involving Ville, Imre, Chris and
Daniel.

v2: More details in the commit.

v3: Use drm_gem_object_unreference_unlocked. (Chris Wilson)

Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: Imre Deak <imre.deak@intel.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>

diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index 0811dd136c5613d606bc23583a5b8b270bbf55c9..4d30bca0b26bae05c35952adea5fffc77b05c117 100644 (file)
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -15971,9 +15971,7 @@ void intel_modeset_gem_init(struct drm_device *dev)
        struct drm_i915_gem_object *obj;
        int ret;
 
-       mutex_lock(&dev->struct_mutex);
        intel_init_gt_powersave(dev);
-       mutex_unlock(&dev->struct_mutex);
 
        intel_modeset_init_hw(dev);
 
@@ -16053,9 +16051,7 @@ void intel_modeset_cleanup(struct drm_device *dev)
 
        intel_cleanup_overlay(dev);
 
-       mutex_lock(&dev->struct_mutex);
        intel_cleanup_gt_powersave(dev);
-       mutex_unlock(&dev->struct_mutex);
 
        intel_teardown_gmbus(dev);
 }

diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
index 379eabe093cb4195d79412080078ae423c372848..8e869f183404093f8eca597aba5fefcb76fba863 100644 (file)
--- a/drivers/gpu/drm/i915/intel_pm.c
+++ b/drivers/gpu/drm/i915/intel_pm.c
@@ -5229,8 +5229,6 @@ static void cherryview_setup_pctx(struct drm_device *dev)
        u32 pcbr;
        int pctx_size = 32*1024;
 
-       WARN_ON(!mutex_is_locked(&dev->struct_mutex));
-
        pcbr = I915_READ(VLV_PCBR);
        if ((pcbr >> VLV_PCBR_ADDR_SHIFT) == 0) {
                DRM_DEBUG_DRIVER("BIOS didn't set up PCBR, fixing up\n");
@@ -5252,7 +5250,7 @@ static void valleyview_setup_pctx(struct drm_device *dev)
        u32 pcbr;
        int pctx_size = 24*1024;
 
-       WARN_ON(!mutex_is_locked(&dev->struct_mutex));
+       mutex_lock(&dev->struct_mutex);
 
        pcbr = I915_READ(VLV_PCBR);
        if (pcbr) {
@@ -5280,7 +5278,7 @@ static void valleyview_setup_pctx(struct drm_device *dev)
        pctx = i915_gem_object_create_stolen(dev, pctx_size);
        if (!pctx) {
                DRM_DEBUG("not enough stolen space for PCTX, disabling\n");
-               return;
+               goto out;
        }
 
        pctx_paddr = dev_priv->mm.stolen_base + pctx->stolen->start;
@@ -5289,6 +5287,7 @@ static void valleyview_setup_pctx(struct drm_device *dev)
 out:
        DRM_DEBUG_DRIVER("PCBR: 0x%08x\n", I915_READ(VLV_PCBR));
        dev_priv->vlv_pctx = pctx;
+       mutex_unlock(&dev->struct_mutex);
 }
 
 static void valleyview_cleanup_pctx(struct drm_device *dev)
@@ -5298,7 +5297,7 @@ static void valleyview_cleanup_pctx(struct drm_device *dev)
        if (WARN_ON(!dev_priv->vlv_pctx))
                return;
 
-       drm_gem_object_unreference(&dev_priv->vlv_pctx->base);
+       drm_gem_object_unreference_unlocked(&dev_priv->vlv_pctx->base);
        dev_priv->vlv_pctx = NULL;
 }