On Fri, Jul 19, 2019 at 1:32 PM Sam Ravnborg <sam@xxxxxxxxxxxx> wrote: > > Hi Michael. > > On Fri, Jul 19, 2019 at 11:05:44AM +0200, Michel Dänzer wrote: > > On 2019-07-19 8:07 a.m., Sam Ravnborg wrote: > > > On Thu, Jul 18, 2019 at 05:37:31PM +0200, Sam Ravnborg wrote: > > >> This is some janitorial updates to the via driver > > >> that is required to get rid of deprecated headers > > >> in the drm subsystem. > > >> > > >> The first three patches are trivial, where > > >> the dependencies on drmP.h and drm_os_linux are dropped. > > >> > > >> The remaining three patches drop use of DRM_WAIT_ON(). > > >> They are replaced by wait_event_interruptible_timeout(). > > >> These patches could use a more critical review. > > > > > > The differences between DRM_WAIT_ON() and > > > wait_event_interruptible_timeout() are bigger than anticipated. > > > > > > The conversion I did for drm_vblank.c is bogus thus I expect > > > the conversion done for via is also bogus. > > > > What exactly is the problem though? Can you share information about the > > failures you're seeing? > > > > There was some discussion about DRM_WAIT_ON() "polling" on IRC. I assume > > that refers to it only sleeping for up to 0.01s before checking the > > condition again. In contrast, wait_event_interruptible_timeout() checks > > the condition once, then sleeps up to the full timeout before checking > > it again. > Correct - it was based on the feedback on irc from airlied and ickle > that made me conclude that the via part may not be good. > I cannot say if the polling versus timeout is properly dealt with in the > via driver and I am inclided to just move DRM_WAIT_ON() to via_drv.h and > name it VIA_WAIT_ON(). > Then the changes to this legacy driver is minimal and it will not > prevent us from gettting rid of drm_os_linux.h > > > > > If that makes a difference for drm_wait_vblank_ioctl, it indicates that > > some other code which updates the vblank count or clears vblank->enabled > > doesn't wake up the vblank->queue. > Let me analyse a little... > > In drm_handle_vblank() there is a call to wake_up(&vblank->queue); > And this is called from an interrupt - OK. > > drm_vblank_enable() is called outside an interrupt - no need for > wake_up() > > drm_crtc_accurate_vblank_count() is called outside interrupt - no need > for wake_up() > > drm_vblank_disable_and_save() is called outside interrupt - no need for > wake_up()' > > That is all functions I could dig up that updates the vblank counter. > > So based on this short analysis I actually start to think that > I can use the variant that uses wait_event_interruptible_timeout() > anyway. > I will post a v3 and await feedback on that version. Furthermore the new vblank sequence ioctls that Keith added don't use DRM_WAIT_ON(), so maybe that ship sailed already. -Daniel -- Daniel Vetter Software Engineer, Intel Corporation +41 (0) 79 365 57 48 - http://blog.ffwll.ch _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
