The individual bits inside obj->frontbuffer_bits are protected by each
plane->mutex, but the whole bitfield may be accessed by multiple KMS
operations simultaneously and so the RMW need to be under atomics.
However, for updating the single field we do not need to mandate that it
be under the struct_mutex, one more step towards its removal as the de
facto BKL.
Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Cc: Daniel Vetter <daniel.vetter@xxxxxxxx>
---
drivers/gpu/drm/i915/i915_debugfs.c | 6 ++++--
drivers/gpu/drm/i915/i915_drv.h | 4 +---
drivers/gpu/drm/i915/i915_gem.c | 18 +++++++++++-------
drivers/gpu/drm/i915/intel_display.c | 7 ++++---
drivers/gpu/drm/i915/intel_drv.h | 4 ++--
drivers/gpu/drm/i915/intel_frontbuffer.c | 19 +++++++------------
6 files changed, 29 insertions(+), 29 deletions(-)
diff --git a/drivers/gpu/drm/i915/i915_debugfs.c b/drivers/gpu/drm/i915/i915_debugfs.c
index f4745e0c8d5c..355bbf895c22 100644
--- a/drivers/gpu/drm/i915/i915_debugfs.c
+++ b/drivers/gpu/drm/i915/i915_debugfs.c
@@ -138,6 +138,7 @@ describe_obj(struct seq_file *m, struct drm_i915_gem_object *obj)
struct drm_i915_private *dev_priv = to_i915(obj->base.dev);
struct intel_engine_cs *engine;
struct i915_vma *vma;
+ unsigned frontbuffer_bits;
int pin_count = 0;
enum intel_engine_id id;
@@ -204,8 +205,9 @@ describe_obj(struct seq_file *m, struct drm_i915_gem_object *obj)
if (engine)
seq_printf(m, " (%s)", engine->name);
- if (obj->frontbuffer_bits)
- seq_printf(m, " (frontbuffer: 0x%03x)", obj->frontbuffer_bits);
+ frontbuffer_bits = atomic_read(&obj->frontbuffer_bits);
+ if (frontbuffer_bits)
+ seq_printf(m, " (frontbuffer: 0x%03x)", frontbuffer_bits);
}
static int i915_gem_object_list_info(struct seq_file *m, void *data)
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 59846de3b33d..236ade61cade 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -2108,8 +2108,6 @@ struct drm_i915_gem_object_ops {
*/
#define INTEL_MAX_SPRITE_BITS_PER_PIPE 5
#define INTEL_FRONTBUFFER_BITS_PER_PIPE 8
-#define INTEL_FRONTBUFFER_BITS \
- (INTEL_FRONTBUFFER_BITS_PER_PIPE * I915_MAX_PIPES)
#define INTEL_FRONTBUFFER_PRIMARY(pipe) \
(1 << (INTEL_FRONTBUFFER_BITS_PER_PIPE * (pipe)))
#define INTEL_FRONTBUFFER_CURSOR(pipe) \
@@ -2197,7 +2195,7 @@ struct drm_i915_gem_object {
unsigned int cache_level:3;
unsigned int cache_dirty:1;
- unsigned int frontbuffer_bits:INTEL_FRONTBUFFER_BITS;
+ atomic_t frontbuffer_bits;
/** Count of VMA actually bound by this object */
unsigned int bind_count;
diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 522f379c8d44..05425ae7c8a8 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -3746,7 +3746,7 @@ void i915_gem_free_object(struct drm_gem_object *gem_obj)
if (obj->stolen)
i915_gem_object_unpin_pages(obj);
- WARN_ON(obj->frontbuffer_bits);
+ WARN_ON(atomic_read(&obj->frontbuffer_bits));
if (obj->pages && obj->madv == I915_MADV_WILLNEED &&
dev_priv->quirks & QUIRK_PIN_SWIZZLED_PAGES &&
@@ -4288,16 +4288,20 @@ void i915_gem_track_fb(struct drm_i915_gem_object *old,
struct drm_i915_gem_object *new,
unsigned frontbuffer_bits)
{
+ /* Control of individual bits within the bitfield are guarded by
+ * the owning plane->mutex, i.e. we can never see concurrent
+ * manipulation of individual bits. But since the bitfield as a whole
+ * is updated using RMW, we need to use atomics in order to update
+ * the bits.
+ */
if (old) {
- WARN_ON(!mutex_is_locked(&old->base.dev->struct_mutex));
- WARN_ON(!(old->frontbuffer_bits & frontbuffer_bits));
- old->frontbuffer_bits &= ~frontbuffer_bits;
+ WARN_ON(!(atomic_read(&old->frontbuffer_bits) & frontbuffer_bits));
+ atomic_andnot(frontbuffer_bits, &old->frontbuffer_bits);
}
if (new) {
- WARN_ON(!mutex_is_locked(&new->base.dev->struct_mutex));
- WARN_ON(new->frontbuffer_bits & frontbuffer_bits);
- new->frontbuffer_bits |= frontbuffer_bits;
+ WARN_ON(atomic_read(&new->frontbuffer_bits) & frontbuffer_bits);
+ atomic_or(frontbuffer_bits, &new->frontbuffer_bits);
}
}
diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index 82533f1da54c..0cfaace38370 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -2635,7 +2635,8 @@ valid_fb:
primary->fb = primary->state->fb = fb;
primary->crtc = primary->state->crtc = &intel_crtc->base;
intel_crtc->base.state->plane_mask |= (1 << drm_plane_index(primary));
- obj->frontbuffer_bits |= to_intel_plane(primary)->frontbuffer_bit;
+ atomic_or(to_intel_plane(primary)->frontbuffer_bit,
+ &obj->frontbuffer_bits);
}
static void i9xx_update_primary_plane(struct drm_plane *primary,
@@ -14012,8 +14013,8 @@ intel_cleanup_plane_fb(struct drm_plane *plane,
intel_unpin_fb_obj(old_state->fb, old_state->rotation);
/* prepare_fb aborted? */
- if ((old_obj && (old_obj->frontbuffer_bits & intel_plane->frontbuffer_bit)) ||
- (obj && !(obj->frontbuffer_bits & intel_plane->frontbuffer_bit)))
+ if ((old_obj && (atomic_read(&old_obj->frontbuffer_bits) & intel_plane->frontbuffer_bit)) ||
+ (obj && !(atomic_read(&obj->frontbuffer_bits) & intel_plane->frontbuffer_bit)))
i915_gem_track_fb(old_obj, obj, intel_plane->frontbuffer_bit);
i915_gem_request_assign(&old_intel_state->wait_req, NULL);
diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
index 9410767c97da..834646b4cc3f 100644
--- a/drivers/gpu/drm/i915/intel_drv.h
+++ b/drivers/gpu/drm/i915/intel_drv.h
@@ -1122,7 +1122,7 @@ void __intel_fb_obj_invalidate(struct drm_i915_gem_object *obj,
static inline void intel_fb_obj_invalidate(struct drm_i915_gem_object *obj,
enum fb_op_origin origin)
{
- if (!obj->frontbuffer_bits || !obj->pin_display)
+ if (!atomic_read(&obj->frontbuffer_bits) || !obj->pin_display)
return;
__intel_fb_obj_invalidate(obj, origin);
@@ -1135,7 +1135,7 @@ static inline void intel_fb_obj_flush(struct drm_i915_gem_object *obj,
bool retire,
enum fb_op_origin origin)
{
- if (!obj->frontbuffer_bits || !obj->pin_display)
+ if (!atomic_read(&obj->frontbuffer_bits) || !obj->pin_display)
return;
__intel_fb_obj_flush(obj, retire, origin);
diff --git a/drivers/gpu/drm/i915/intel_frontbuffer.c b/drivers/gpu/drm/i915/intel_frontbuffer.c
index a38ccfe4894a..8af291d22589 100644
--- a/drivers/gpu/drm/i915/intel_frontbuffer.c
+++ b/drivers/gpu/drm/i915/intel_frontbuffer.c
@@ -81,19 +81,18 @@ void __intel_fb_obj_invalidate(struct drm_i915_gem_object *obj,
{
struct drm_device *dev = obj->base.dev;
struct drm_i915_private *dev_priv = to_i915(dev);
-
- WARN_ON(!mutex_is_locked(&dev->struct_mutex));
+ unsigned frontbuffer_bits = atomic_read(&obj->frontbuffer_bits);
if (origin == ORIGIN_CS) {
spin_lock(&dev_priv->fb_tracking.lock);
- dev_priv->fb_tracking.busy_bits |= obj->frontbuffer_bits;
- dev_priv->fb_tracking.flip_bits &= ~obj->frontbuffer_bits;
+ dev_priv->fb_tracking.busy_bits |= frontbuffer_bits;
+ dev_priv->fb_tracking.flip_bits &= ~frontbuffer_bits;
spin_unlock(&dev_priv->fb_tracking.lock);
}
- intel_psr_invalidate(dev, obj->frontbuffer_bits);
- intel_edp_drrs_invalidate(dev, obj->frontbuffer_bits);
- intel_fbc_invalidate(dev_priv, obj->frontbuffer_bits, origin);
+ intel_psr_invalidate(dev, frontbuffer_bits);
+ intel_edp_drrs_invalidate(dev, frontbuffer_bits);
+ intel_fbc_invalidate(dev_priv, frontbuffer_bits, origin);
}
/**
@@ -143,11 +142,7 @@ void __intel_fb_obj_flush(struct drm_i915_gem_object *obj,
{
struct drm_device *dev = obj->base.dev;
struct drm_i915_private *dev_priv = to_i915(dev);
- unsigned frontbuffer_bits;
-
- WARN_ON(!mutex_is_locked(&dev->struct_mutex));
-
- frontbuffer_bits = obj->frontbuffer_bits;
+ unsigned frontbuffer_bits = atomic_read(&obj->frontbuffer_bits);
if (retire) {
spin_lock(&dev_priv->fb_tracking.lock);
--
2.8.1
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