On Wed, Jan 16, 2013 at 01:36:17PM +0100, Daniel Vetter wrote:
> On Wed, Jan 16, 2013 at 11:01 AM, Thierry Reding
> <thierry.reding@xxxxxxxxxxxxxxxxx> wrote:
> > drm_events_release() should be enough to clean up the events, but I
> > suspect the reason why Laurent put that code in was that the drm_crtc
> > private data still has a reference to the event and needs to clear it.
> > Otherwise the next page flip won't be scheduled because .page_flip()
> > would return -EBUSY.
>
> Hm, indeed we seem to have a nice bug in most drivers there :(
I think I may just recently have run into this bug on Intel hardware.
Although perhaps I just used this wrongly.
Just for the fun of it I wanted to implement Conway's Game of Life on
top of DRM/KMS. So I use two dumb buffer objects to alternately render
to. Then I wanted to use page-flipping to synchronize with VBLANK.
So the sequence is basically:
while (!done) {
grid_tick(grid);
grid_draw(grid, screen);
screen_flip(screen);
grid_swap(grid);
}
Where screen_flip() chooses the framebuffer and passes it to
drmModePageFlip() like so:
int fb = screen->fb[screen->current];
drmModePageFlip(screen->fd, screen->crtc, fb,
DRM_MODE_PAGE_FLIP_EVENT, screen);
This runs for about 3 seconds and then hangs, so the display is no
longer updated. I've also verified that the same happens on Radeon.
But maybe I am mistaken and this isn't the proper programming sequence?
Thierry
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