The explicit out-fences in crtc are signaled as part of vblank event,
indicating all framebuffers present on the Atomic Commit request are
scanned out on the screen. Though the fence signal and the vblank
event
notification happens at the same time, triggered by the same hardware
vsync event, the timestamp set in both are different. With drivers
supporting precise vblank timestamp the difference between the two
timestamps would be even higher. This might have an impact on use-mode
frameworks using these fence timestamps for purposes other than simple
buffer usage. For instance, the Android framework [1] uses the
retire-fences as an alternative to vblank when frame-updates are in
progress. Set the fence timestamp during send vblank event using a new
drm_send_event_timestamp_locked variant to avoid discrepancies.
[1]
https://android.googlesource.com/platform/frameworks/native/+/master/
services/surfaceflinger/Scheduler/Scheduler.cpp#397
Changes in v2:
- Use drm_send_event_timestamp_locked to update fence timestamp
- add more information to commit text
Changes in v3:
- use same backend helper function for variants of drm_send_event to
avoid code duplications
Signed-off-by: Veera Sundaram Sankaran <veeras@xxxxxxxxxxxxxx>
---
drivers/gpu/drm/drm_file.c | 71
++++++++++++++++++++++++++++++++++++--------
drivers/gpu/drm/drm_vblank.c | 9 +++++-
include/drm/drm_file.h | 3 ++
3 files changed, 70 insertions(+), 13 deletions(-)
diff --git a/drivers/gpu/drm/drm_file.c b/drivers/gpu/drm/drm_file.c
index 0ac4566..b8348ca 100644
--- a/drivers/gpu/drm/drm_file.c
+++ b/drivers/gpu/drm/drm_file.c
@@ -775,20 +775,19 @@ void drm_event_cancel_free(struct drm_device
*dev,
EXPORT_SYMBOL(drm_event_cancel_free);
/**
- * drm_send_event_locked - send DRM event to file descriptor
+ * drm_send_event_helper - send DRM event to file descriptor
* @dev: DRM device
* @e: DRM event to deliver
+ * @timestamp: timestamp to set for the fence event in kernel's
CLOCK_MONOTONIC
+ * time domain
*
- * This function sends the event @e, initialized with
drm_event_reserve_init(),
- * to its associated userspace DRM file. Callers must already hold
- * &drm_device.event_lock, see drm_send_event() for the unlocked
version.
- *
- * Note that the core will take care of unlinking and disarming
events when the
- * corresponding DRM file is closed. Drivers need not worry about
whether the
- * DRM file for this event still exists and can call this function
upon
- * completion of the asynchronous work unconditionally.
+ * This helper function sends the event @e, initialized with
+ * drm_event_reserve_init(), to its associated userspace DRM file.
+ * The timestamp variant of dma_fence_signal is used when the caller
+ * sends a valid timestamp.
*/
-void drm_send_event_locked(struct drm_device *dev, struct
drm_pending_event *e)
+void drm_send_event_helper(struct drm_device *dev,
+ struct drm_pending_event *e, ktime_t
timestamp)
{
assert_spin_locked(&dev->event_lock);
@@ -799,7 +798,10 @@ void drm_send_event_locked(struct drm_device
*dev, struct drm_pending_event *e)
}
if (e->fence) {
- dma_fence_signal(e->fence);
+ if (timestamp)
+ dma_fence_signal_timestamp(e->fence,
timestamp);
+ else
+ dma_fence_signal(e->fence);
dma_fence_put(e->fence);
}
@@ -814,6 +816,51 @@ void drm_send_event_locked(struct drm_device
*dev, struct drm_pending_event *e)
wake_up_interruptible_poll(&e->file_priv->event_wait,
EPOLLIN | EPOLLRDNORM);
}
+
+/**
+ * drm_send_event_timestamp_locked - send DRM event to file
descriptor
+ * @dev: DRM device
+ * @e: DRM event to deliver
+ * @timestamp: timestamp to set for the fence event in kernel's
CLOCK_MONOTONIC
+ * time domain
+ *
+ * This function sends the event @e, initialized with
drm_event_reserve_init(),
+ * to its associated userspace DRM file. Callers must already hold
+ * &drm_device.event_lock.
+ *
+ * Note that the core will take care of unlinking and disarming
events when the
+ * corresponding DRM file is closed. Drivers need not worry about
whether the
+ * DRM file for this event still exists and can call this function
upon
+ * completion of the asynchronous work unconditionally.
+ */
+void drm_send_event_timestamp_locked(struct drm_device *dev,
+ struct drm_pending_event *e, ktime_t
timestamp)
+{
+ WARN_ON(!timestamp);
+
+ drm_send_event_helper(dev, e, timestamp);
+
+}
+EXPORT_SYMBOL(drm_send_event_timestamp_locked);
