On Tue, Jul 28, 2020 at 04:16:34PM +0000, Sidong Yang wrote: > On Sun, Jul 26, 2020 at 12:26:08PM +0200, Daniel Vetter wrote: > > On Sat, Jul 25, 2020 at 9:29 PM Melissa Wen <melissa....@gmail.com> wrote: > > > > > > On Sat, Jul 25, 2020 at 4:19 PM Melissa Wen <melissa....@gmail.com> wrote: > > > > > > > > > No, this very first warning continues (only once) :( > > > > > From here (drm_crtc_vblank_on): > > > > > if (atomic_read(&vblank->refcount) != 0 || > > > > > drm_vblank_offdelay == 0) > > > > > drm_WARN_ON(dev, drm_vblank_enable(dev, pipe)); > > > > > > > > Sorry, not sure when this warning is triggered. > > > > > > Again, I just had to look at the trace: > > > [ 52.299388] drm_get_last_vbltimestamp+0xaa/0xc0 [drm] > > > [ 52.299389] drm_reset_vblank_timestamp+0x5b/0xd0 [drm] > > > [ 52.299389] drm_crtc_vblank_on.cold+0x37/0x103 [drm] > > > [ 52.299390] drm_atomic_helper_commit_modeset_enable > > > > Yeah I think vkms can't generate a reasonable timestamp when the > > hrtimer is off. I thought the warning comes from a different > > callchain, but seems to be a general problem. > > > > I guess in the vkms timestamp function we should check whether the > > timer is running, and if it's not running, then we just grab the > > current time and done. > > I tried some test about this scenario that commit_tail calls in sequence > disable > - enable - commit. > In a first test. there was a warning and found out that it raised from > vkms_get_vblank_timestamp() the code checking vblank_hrtimer's expire time > and > vblank_time. In first run, vblank_time and hrtimer's expire time was both > zero. > because vblank wasn't happened yet. this warning wasn't happend since second > run > that vblank time was set from first run. > > I don't know it's good way to solve the problem. Is there no problem in other > drm modules?
Generally real hw drivers always have working clocks, not like the fake ones we have here :-) The idea behind the timestamp callback is that when vblank interrupts aren't enabled, the timestamp will help us keep track of how many vblanks have happened. So I think (but might be wrong) correct fix for this issue would be to check whether vblanks are enabled, and if not, simply pass back the current system time. That's a lie, but much better than whatever value was set last time around the hrtimer fired- e.g. similar problem can happen later on when the vblank interrupt was off for a very long time. -Daniel > > -Sidong > > > -Daniel > > > > > > > > > > > > > > > > > But I'm still wondering why after step 3 we don't get -EINVAL from > > > > > > vblank_get() - after vblank_off() vblank->enabled should be false > > > > > > again, getting us back to the same state as after 1. Is that not > > > > > > happening? > > > > > > > > > > Yes (sorry if it got confused), we got -EINVAL after setp 3: > > > > > > > > > > In step 3, at the end of the 2nd running, we have: > > > > > atomic_disable > > > > > --> vblank_off [!vblank->inmodeset + refcount going 0->1 + > > > > > inmodeset=1] > > > > > and then in next vblank_get: -EINVAL (!vblank->enabled + refcount > > > > > ends 1) > > > > > as in the first step. > > > > > > > > > > Melissa > > > > > > > > > > > -Daniel > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > Thanks > > > > > > > > > -Sidong > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > crtc->state->event = NULL; > > > > > > > > > > > > > } > > > > > > > > > > > > > > > > > > > > > > > > > > -- > > > > > > > > > > > > > 2.27.0 > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > -- > > > > > > > > > > > > Daniel Vetter > > > > > > > > > > > > Software Engineer, Intel Corporation > > > > > > > > > > > > http://blog.ffwll.ch > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > -- > > > > > > > > > > Daniel Vetter > > > > > > > > > > Software Engineer, Intel Corporation > > > > > > > > > > http://blog.ffwll.ch > > > > > > > > > > _______________________________________________ > > > > > > > > > > dri-devel mailing list > > > > > > > > > > dri-de...@lists.freedesktop.org > > > > > > > > > > https://lists.freedesktop.org/mailman/listinfo/dri-devel > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > -- > > > > > > > > Daniel Vetter > > > > > > > > Software Engineer, Intel Corporation > > > > > > > > http://blog.ffwll.ch > > > > > > > > > > > > > > > > > > > > > > > > -- > > > > > > Daniel Vetter > > > > > > Software Engineer, Intel Corporation > > > > > > http://blog.ffwll.ch > > > > > > > > -- > > Daniel Vetter > > Software Engineer, Intel Corporation > > http://blog.ffwll.ch -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch
