[PATCH 4/7] drm/i915: add the FBC mutex

[Paulo Zanoni <przanoni@gmail.com>]

From: Paulo Zanoni <paulo.r.zanoni@intel.com>

Make sure we're not going to have weird races in really weird cases
where a lot of different CRTCs are doing rendering and modesets at the
same time.

With this change and the stolen_lock from the previous patch, we can start
removing the struct_mutex locking we have around FBC in the next patches.

v2:
 - Rebase (6 months later)
 - Also lock debugfs and stolen.
v3:
 - Don't lock a single value read (Chris).
 - Replace lockdep assertions with WARNs (Daniel).
 - Improve commit message.
 - Don't forget intel_pre_plane_update() locking.
v4:
 - Don't remove struct_mutex at intel_pre_plane_update() (Chris).
 - Add comment regarding locking dependencies (Chris).
 - Rebase after the stolen code rework.
 - Rebase again after drm-intel-nightly changes.

Signed-off-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
---
 drivers/gpu/drm/i915/i915_debugfs.c  |  4 ++
 drivers/gpu/drm/i915/i915_drv.h      |  3 ++
 drivers/gpu/drm/i915/intel_display.c |  6 +--
 drivers/gpu/drm/i915/intel_drv.h     |  1 +
 drivers/gpu/drm/i915/intel_fbc.c     | 94 +++++++++++++++++++++++++++++++-----
 5 files changed, 91 insertions(+), 17 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_debugfs.c b/drivers/gpu/drm/i915/i915_debugfs.c
index 71ba519..b2f3919 100644
--- a/drivers/gpu/drm/i915/i915_debugfs.c
+++ b/drivers/gpu/drm/i915/i915_debugfs.c
@@ -1633,6 +1633,7 @@ static int i915_fbc_status(struct seq_file *m, void *unused)
 	}
 
 	intel_runtime_pm_get(dev_priv);
+	mutex_lock(&dev_priv->fbc.lock);
 
 	if (intel_fbc_enabled(dev))
 		seq_puts(m, "FBC enabled\n");
@@ -1645,6 +1646,7 @@ static int i915_fbc_status(struct seq_file *m, void *unused)
 			   yesno(I915_READ(FBC_STATUS2) &
 				 FBC_COMPRESSION_MASK));
 
+	mutex_unlock(&dev_priv->fbc.lock);
 	intel_runtime_pm_put(dev_priv);
 
 	return 0;
@@ -1675,6 +1677,7 @@ static int i915_fbc_fc_set(void *data, u64 val)
 		return -ENODEV;
 
 	drm_modeset_lock_all(dev);
+	mutex_lock(&dev_priv->fbc.lock);
 
 	reg = I915_READ(ILK_DPFC_CONTROL);
 	dev_priv->fbc.false_color = val;
@@ -1683,6 +1686,7 @@ static int i915_fbc_fc_set(void *data, u64 val)
 		   (reg | FBC_CTL_FALSE_COLOR) :
 		   (reg & ~FBC_CTL_FALSE_COLOR));
 
+	mutex_unlock(&dev_priv->fbc.lock);
 	drm_modeset_unlock_all(dev);
 	return 0;
 }
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 0b908b1..4d3d4103 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -899,6 +899,9 @@ enum fb_op_origin {
 };
 
 struct i915_fbc {
+	/* This is always the inner lock when overlapping with struct_mutex and
+	 * it's the outer lock when overlapping with stolen_lock. */
+	struct mutex lock;
 	unsigned long uncompressed_size;
 	unsigned threshold;
 	unsigned int fb_id;
diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index 5de1ded..e12ed4f 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -4783,11 +4783,9 @@ static void intel_pre_plane_update(struct intel_crtc *crtc)
 	if (atomic->wait_for_flips)
 		intel_crtc_wait_for_pending_flips(&crtc->base);
 
-	if (atomic->disable_fbc &&
-	    dev_priv->fbc.crtc == crtc) {
+	if (atomic->disable_fbc) {
 		mutex_lock(&dev->struct_mutex);
-		if (dev_priv->fbc.crtc == crtc)
-			intel_fbc_disable(dev);
+		intel_fbc_disable_crtc(crtc);
 		mutex_unlock(&dev->struct_mutex);
 	}
 
diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
index 82abbfa..63d7d32 100644
--- a/drivers/gpu/drm/i915/intel_drv.h
+++ b/drivers/gpu/drm/i915/intel_drv.h
@@ -1252,6 +1252,7 @@ bool intel_fbc_enabled(struct drm_device *dev);
 void intel_fbc_update(struct drm_device *dev);
 void intel_fbc_init(struct drm_i915_private *dev_priv);
 void intel_fbc_disable(struct drm_device *dev);
+void intel_fbc_disable_crtc(struct intel_crtc *crtc);
 void intel_fbc_invalidate(struct drm_i915_private *dev_priv,
 			  unsigned int frontbuffer_bits,
 			  enum fb_op_origin origin);
diff --git a/drivers/gpu/drm/i915/intel_fbc.c b/drivers/gpu/drm/i915/intel_fbc.c
index dcd83ab..3a98bc1 100644
--- a/drivers/gpu/drm/i915/intel_fbc.c
+++ b/drivers/gpu/drm/i915/intel_fbc.c
@@ -336,6 +336,7 @@ static void intel_fbc_work_fn(struct work_struct *__work)
 	struct drm_i915_private *dev_priv = dev->dev_private;
 
 	mutex_lock(&dev->struct_mutex);
+	mutex_lock(&dev_priv->fbc.lock);
 	if (work == dev_priv->fbc.fbc_work) {
 		/* Double check that we haven't switched fb without cancelling
 		 * the prior work.
@@ -350,6 +351,7 @@ static void intel_fbc_work_fn(struct work_struct *__work)
 
 		dev_priv->fbc.fbc_work = NULL;
 	}
+	mutex_unlock(&dev_priv->fbc.lock);
 	mutex_unlock(&dev->struct_mutex);
 
 	kfree(work);
@@ -357,6 +359,8 @@ static void intel_fbc_work_fn(struct work_struct *__work)
 
 static void intel_fbc_cancel_work(struct drm_i915_private *dev_priv)
 {
+	WARN_ON(!mutex_is_locked(&dev_priv->fbc.lock));
+
 	if (dev_priv->fbc.fbc_work == NULL)
 		return;
 
@@ -384,6 +388,8 @@ static void intel_fbc_enable(struct drm_crtc *crtc)
 	struct drm_device *dev = crtc->dev;
 	struct drm_i915_private *dev_priv = dev->dev_private;
 
+	WARN_ON(!mutex_is_locked(&dev_priv->fbc.lock));
+
 	if (!dev_priv->display.enable_fbc)
 		return;
 
@@ -418,6 +424,21 @@ static void intel_fbc_enable(struct drm_crtc *crtc)
 	schedule_delayed_work(&work->work, msecs_to_jiffies(50));
 }
 
+static void __intel_fbc_disable(struct drm_device *dev)
+{
+	struct drm_i915_private *dev_priv = dev->dev_private;
+
+	WARN_ON(!mutex_is_locked(&dev_priv->fbc.lock));
+
+	intel_fbc_cancel_work(dev_priv);
+
+	if (!dev_priv->display.disable_fbc)
+		return;
+
+	dev_priv->display.disable_fbc(dev);
+	dev_priv->fbc.crtc = NULL;
+}
+
 /**
  * intel_fbc_disable - disable FBC
  * @dev: the drm_device
@@ -428,13 +449,26 @@ void intel_fbc_disable(struct drm_device *dev)
 {
 	struct drm_i915_private *dev_priv = dev->dev_private;
 
-	intel_fbc_cancel_work(dev_priv);
+	mutex_lock(&dev_priv->fbc.lock);
+	__intel_fbc_disable(dev);
+	mutex_unlock(&dev_priv->fbc.lock);
+}
 
-	if (!dev_priv->display.disable_fbc)
-		return;
+/*
+ * intel_fbc_disable_crtc - disable FBC if it's associated with crtc
+ * @crtc: the CRTC
+ *
+ * This function disables FBC if it's associated with the provided CRTC.
+ */
+void intel_fbc_disable_crtc(struct intel_crtc *crtc)
+{
+	struct drm_device *dev = crtc->base.dev;
+	struct drm_i915_private *dev_priv = dev->dev_private;
 
-	dev_priv->display.disable_fbc(dev);
-	dev_priv->fbc.crtc = NULL;
+	mutex_lock(&dev_priv->fbc.lock);
+	if (dev_priv->fbc.crtc == crtc)
+		__intel_fbc_disable(dev);
+	mutex_unlock(&dev_priv->fbc.lock);
 }
 
 const char *intel_no_fbc_reason_str(enum no_fbc_reason reason)
@@ -629,9 +663,13 @@ void intel_fbc_cleanup_cfb(struct drm_device *dev)
 {
 	struct drm_i915_private *dev_priv = dev->dev_private;
 
+	mutex_lock(&dev_priv->fbc.lock);
 	mutex_lock(&dev_priv->mm.stolen_lock);
+
 	__intel_fbc_cleanup_cfb(dev);
+
 	mutex_unlock(&dev_priv->mm.stolen_lock);
+	mutex_unlock(&dev_priv->fbc.lock);
 }
 
 static int intel_fbc_setup_cfb(struct drm_device *dev, int size, int fb_cpp)
@@ -655,7 +693,7 @@ static int intel_fbc_setup_cfb(struct drm_device *dev, int size, int fb_cpp)
 }
 
 /**
- * intel_fbc_update - enable/disable FBC as needed
+ * __intel_fbc_update - enable/disable FBC as needed, unlocked
  * @dev: the drm_device
  *
  * Set up the framebuffer compression hardware at mode set time.  We
@@ -673,7 +711,7 @@ static int intel_fbc_setup_cfb(struct drm_device *dev, int size, int fb_cpp)
  *
  * We need to enable/disable FBC on a global basis.
  */
-void intel_fbc_update(struct drm_device *dev)
+static void __intel_fbc_update(struct drm_device *dev)
 {
 	struct drm_i915_private *dev_priv = dev->dev_private;
 	struct drm_crtc *crtc = NULL;
@@ -683,6 +721,8 @@ void intel_fbc_update(struct drm_device *dev)
 	const struct drm_display_mode *adjusted_mode;
 	unsigned int max_width, max_height;
 
+	WARN_ON(!mutex_is_locked(&dev_priv->fbc.lock));
+
 	if (!HAS_FBC(dev))
 		return;
 
@@ -804,7 +844,7 @@ void intel_fbc_update(struct drm_device *dev)
 		 * some point. And we wait before enabling FBC anyway.
 		 */
 		DRM_DEBUG_KMS("disabling active FBC for update\n");
-		intel_fbc_disable(dev);
+		__intel_fbc_disable(dev);
 	}
 
 	intel_fbc_enable(crtc);
@@ -815,9 +855,26 @@ out_disable:
 	/* Multiple disables should be harmless */
 	if (intel_fbc_enabled(dev)) {
 		DRM_DEBUG_KMS("unsupported config, disabling FBC\n");
-		intel_fbc_disable(dev);
+		__intel_fbc_disable(dev);
 	}
-	intel_fbc_cleanup_cfb(dev);
+	mutex_lock(&dev_priv->mm.stolen_lock);
+	__intel_fbc_cleanup_cfb(dev);
+	mutex_unlock(&dev_priv->mm.stolen_lock);
+}
+
+/*
+ * intel_fbc_update - enable/disable FBC as needed
+ * @dev: the drm_device
+ *
+ * This function reevaluates the overall state and enables or disables FBC.
+ */
+void intel_fbc_update(struct drm_device *dev)
+{
+	struct drm_i915_private *dev_priv = dev->dev_private;
+
+	mutex_lock(&dev_priv->fbc.lock);
+	__intel_fbc_update(dev);
+	mutex_unlock(&dev_priv->fbc.lock);
 }
 
 void intel_fbc_invalidate(struct drm_i915_private *dev_priv,
@@ -830,6 +887,8 @@ void intel_fbc_invalidate(struct drm_i915_private *dev_priv,
 	if (origin == ORIGIN_GTT)
 		return;
 
+	mutex_lock(&dev_priv->fbc.lock);
+
 	if (dev_priv->fbc.enabled)
 		fbc_bits = INTEL_FRONTBUFFER_PRIMARY(dev_priv->fbc.crtc->pipe);
 	else if (dev_priv->fbc.fbc_work)
@@ -841,7 +900,9 @@ void intel_fbc_invalidate(struct drm_i915_private *dev_priv,
 	dev_priv->fbc.busy_bits |= (fbc_bits & frontbuffer_bits);
 
 	if (dev_priv->fbc.busy_bits)
-		intel_fbc_disable(dev);
+		__intel_fbc_disable(dev);
+
+	mutex_unlock(&dev_priv->fbc.lock);
 }
 
 void intel_fbc_flush(struct drm_i915_private *dev_priv,
@@ -849,13 +910,18 @@ void intel_fbc_flush(struct drm_i915_private *dev_priv,
 {
 	struct drm_device *dev = dev_priv->dev;
 
+	mutex_lock(&dev_priv->fbc.lock);
+
 	if (!dev_priv->fbc.busy_bits)
-		return;
+		goto out;
 
 	dev_priv->fbc.busy_bits &= ~frontbuffer_bits;
 
 	if (!dev_priv->fbc.busy_bits)
-		intel_fbc_update(dev);
+		__intel_fbc_update(dev);
+
+out:
+	mutex_unlock(&dev_priv->fbc.lock);
 }
 
 /**
@@ -868,6 +934,8 @@ void intel_fbc_init(struct drm_i915_private *dev_priv)
 {
 	enum pipe pipe;
 
+	mutex_init(&dev_priv->fbc.lock);
+
 	if (!HAS_FBC(dev_priv)) {
 		dev_priv->fbc.enabled = false;
 		dev_priv->fbc.no_fbc_reason = FBC_UNSUPPORTED;
-- 
2.1.4

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