Hi Daniel,
On 29.09.2016 11:44, Daniel Vetter wrote:
On Tue, Sep 27, 2016 at 03:36:14PM +0200, Andrzej Hajda wrote:
A lot of drivers need to fire pageflip completion event at very next vblank interrupt. The patch adds helper to perform this operation. drm_crtc_arm_completion_event checks if there is an event to handle, if vblank reference get succeeds it arms the event, otherwise it sends the event immediately.
Signed-off-by: Andrzej Hajda a.hajda@samsung.com
drivers/gpu/drm/drm_irq.c | 25 +++++++++++++++++++++++++ include/drm/drm_irq.h | 1 + 2 files changed, 26 insertions(+)
diff --git a/drivers/gpu/drm/drm_irq.c b/drivers/gpu/drm/drm_irq.c index 77f357b..313d323 100644 --- a/drivers/gpu/drm/drm_irq.c +++ b/drivers/gpu/drm/drm_irq.c @@ -1053,6 +1053,31 @@ void drm_crtc_send_vblank_event(struct drm_crtc *crtc, EXPORT_SYMBOL(drm_crtc_send_vblank_event);
/**
- drm_crtc_arm_completion_event - conditionally arm crtc completion event
- @crtc: the source CRTC of the completion event
- A lot of drivers need to fire pageflip completion event at very next vblank
- interrupt. This helper tries to arm the event in case of successful vblank
- get otherwise it sends the event immediately.
This function is copypasted tons of times over all drivers because they were broken, and this hack at least got the events working. But in general this here is racy, and if Mario ever runs on your hw he'll get upset about the wrong timings.
Could you explain what is racy here? I am not vblank expert, but the code for me looked more or less OK.
If we go with this (and I'm really not convinced it's a good idea) then it should have real big warning that you should never use this in a new driver.
It looked to me as an easy copy/paste cleaning :) Anyway I would like to have correct solution, at least in case of exynos.
- */
+void drm_crtc_arm_completion_event(struct drm_crtc *crtc) +{
- struct drm_pending_vblank_event *event = crtc->state->event;
- if (event) {
crtc->state->event = NULL;spin_lock_irq(&crtc->dev->event_lock);if (drm_crtc_vblank_get(crtc) == 0)This check here completely torpedoes the design principle of atomic helpers that drivers always know the state of the crtc. Again I only did this because I didn't want to buy hw&test it for all the drivers which got this wrong.
If you mean driver should know that getting vblank should be possible or not this code could be probably parametrized, for example:
drm_crtc_handle_completion_event(struct drm_crtc *crtc, bool send_immediately)
drm_crtc_arm_vblank_event(crtc, event);elsedrm_crtc_send_vblank_event(crtc, event);spin_unlock_irq(&crtc->dev->event_lock);- }
+} +EXPORT_SYMBOL(drm_crtc_arm_completion_event);
Maybe we need an EXPORT_SYMBOL_BROKEN for this .... btw the kerneldoc of the functions you're called do explain that this is not as easy as it seems. That's also something you throw under the rug here. -Daniel
After quick look I have not found these kerneldocs, where can read about it.
Regards Andrzej