Add warning when about to send stale vblank.
Revert change that stops vblank info being updated if interrupts already
disabled. This fixes a stale vblank timestamp issue seen on drm/imx.
Changes since v2:
Split up the patch in to smaller pieces.
Add warning when about to send bogus vblank event.
Update vblank to best guess info during drm_vblank_disable_and_save.
Changes since v3:
Update cover letter text to describe remaining actions.
Drop drm/imx patches as they have now been merged.
Replace vblank info estimation patch with a revert of the issue that
caused the need for estimation.
Robert Beckett (2):
drm/vblank: warn on sending stale event
Revert "drm/vblank: Do not update vblank count if interrupts are
already disabled."
drivers/gpu/drm/drm_vblank.c | 35 +++++++++++++++++++++++++----------
1 file changed, 25 insertions(+), 10 deletions(-)
--
2.18.0
Warn when about to send stale vblank info and add advice to
documentation on how to avoid.
Signed-off-by: Robert Beckett <[email protected]>
---
drivers/gpu/drm/drm_vblank.c | 17 +++++++++++++++++
1 file changed, 17 insertions(+)
diff --git a/drivers/gpu/drm/drm_vblank.c b/drivers/gpu/drm/drm_vblank.c
index 603ab105125d..7dabb2bdb733 100644
--- a/drivers/gpu/drm/drm_vblank.c
+++ b/drivers/gpu/drm/drm_vblank.c
@@ -918,6 +918,19 @@ EXPORT_SYMBOL(drm_crtc_arm_vblank_event);
*
* See drm_crtc_arm_vblank_event() for a helper which can be used in certain
* situation, especially to send out events for atomic commit operations.
+ *
+ * Care should be taken to avoid stale timestamps. If:
+ * - your driver has vblank support (i.e. dev->num_crtcs > 0)
+ * - the vblank irq is off (i.e. no one called drm_crtc_vblank_get)
+ * - from the vblank code's pov the pipe is still running (i.e. not
+ * in-between a drm_crtc_vblank_off()/on() pair)
+ * If all of these conditions hold then drm_crtc_send_vblank_event is
+ * going to give you a garbage timestamp and and sequence number (the last
+ * recorded before the irq was disabled). If you call drm_crtc_vblank_get/put
+ * around it, or after vblank_off, then either of those will have rolled things
+ * forward for you.
+ * So, drivers should call drm_crtc_vblank_off() before this function in their
+ * crtc atomic_disable handlers.
*/
void drm_crtc_send_vblank_event(struct drm_crtc *crtc,
struct drm_pending_vblank_event *e)
@@ -925,8 +938,12 @@ void drm_crtc_send_vblank_event(struct drm_crtc *crtc,
struct drm_device *dev = crtc->dev;
u64 seq;
unsigned int pipe = drm_crtc_index(crtc);
+ struct drm_vblank_crtc *vblank = &dev->vblank[pipe];
ktime_t now;
+ WARN_ONCE(dev->num_crtcs > 0 && !vblank->enabled && !vblank->inmodeset,
+ "sending stale vblank info\n");
+
if (dev->num_crtcs > 0) {
seq = drm_vblank_count_and_time(dev, pipe, &now);
} else {
--
2.18.0
Nak - I forgot the requested doc changes. Ill re-send
On Fri, 2019-06-28 at 13:05 +0100, Robert Beckett wrote:
> Warn when about to send stale vblank info and add advice to
> documentation on how to avoid.
>
> Signed-off-by: Robert Beckett <[email protected]>
> ---
> drivers/gpu/drm/drm_vblank.c | 17 +++++++++++++++++
> 1 file changed, 17 insertions(+)
>
> diff --git a/drivers/gpu/drm/drm_vblank.c
> b/drivers/gpu/drm/drm_vblank.c
> index 603ab105125d..7dabb2bdb733 100644
> --- a/drivers/gpu/drm/drm_vblank.c
> +++ b/drivers/gpu/drm/drm_vblank.c
> @@ -918,6 +918,19 @@ EXPORT_SYMBOL(drm_crtc_arm_vblank_event);
> *
> * See drm_crtc_arm_vblank_event() for a helper which can be used in
> certain
> * situation, especially to send out events for atomic commit
> operations.
> + *
> + * Care should be taken to avoid stale timestamps. If:
> + * - your driver has vblank support (i.e. dev->num_crtcs > 0)
> + * - the vblank irq is off (i.e. no one called
> drm_crtc_vblank_get)
> + * - from the vblank code's pov the pipe is still running (i.e.
> not
> + * in-between a drm_crtc_vblank_off()/on() pair)
> + * If all of these conditions hold then drm_crtc_send_vblank_event
> is
> + * going to give you a garbage timestamp and and sequence number
> (the last
> + * recorded before the irq was disabled). If you call
> drm_crtc_vblank_get/put
> + * around it, or after vblank_off, then either of those will have
> rolled things
> + * forward for you.
> + * So, drivers should call drm_crtc_vblank_off() before this
> function in their
> + * crtc atomic_disable handlers.
> */
> void drm_crtc_send_vblank_event(struct drm_crtc *crtc,
> struct drm_pending_vblank_event *e)
> @@ -925,8 +938,12 @@ void drm_crtc_send_vblank_event(struct drm_crtc
> *crtc,
> struct drm_device *dev = crtc->dev;
> u64 seq;
> unsigned int pipe = drm_crtc_index(crtc);
> + struct drm_vblank_crtc *vblank = &dev->vblank[pipe];
> ktime_t now;
>
> + WARN_ONCE(dev->num_crtcs > 0 && !vblank->enabled && !vblank-
> >inmodeset,
> + "sending stale vblank info\n");
> +
> if (dev->num_crtcs > 0) {
> seq = drm_vblank_count_and_time(dev, pipe, &now);
> } else {