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

Paulo Zanoni
2015-07-01T20:16:10Z

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