On Mon, Jan 25, 2016 at 02:16:45PM +0100, Mario Kleiner wrote: > > > On 01/25/2016 05:15 AM, Michel Dänzer wrote: > > On 23.01.2016 00:18, Ville Syrjälä wrote: > >> On Fri, Jan 22, 2016 at 12:06:00PM +0900, Michel Dänzer wrote: > >>> > >>> [ Trimming KDE folks from Cc ] > >>> > >>> On 21.01.2016 19:09, Daniel Vetter wrote: > >>>> On Thu, Jan 21, 2016 at 05:36:46PM +0900, Michel Dänzer wrote: > >>>>> On 21.01.2016 16:58, Daniel Vetter wrote: > >>>>>> > >>>>>> Can you please point me at the vblank on/off jump bug please? > >>>>> > >>>>> AFAIR I originally reported it in response to > >>>>> http://lists.freedesktop.org/archives/dri-devel/2015-August/087841.html > >>>>> , but I can't find that in the archives, so maybe that was just on IRC. > >>>>> See > >>>>> http://lists.freedesktop.org/archives/dri-devel/2016-January/099122.html > >>>>> . Basically, I ran into the bug fixed by your patch because the counter > >>>>> jumped forward on every DPMS off, so it hit the 32-bit boundary after > >>>>> just a few days. > >>>> > >>>> Ok, so just uncovered the overflow bug. > >>> > >>> Not sure what you mean by "just", but to be clear: The drm_vblank_on/off > >>> counter jumping bug (similar to the bug this thread is about), which > >>> exposed the overflow bug, is still alive and kicking in 4.5. It seems > >>> to happen when turning off the CRTC: > >>> > >>> [drm:drm_update_vblank_count] updating vblank count on crtc 0: current=218104694, diff=0, hw=916 hw_last=916 > >>> [drm:radeon_get_vblank_counter_kms] crtc 0: dist from vblank start 3 > >>> [drm:drm_calc_vbltimestamp_from_scanoutpos] crtc 0 : v 0x7 p(2199,-45)@ 7304.307354 -> 7304.308006 [e 0 us, 0 rep] > >>> [drm:radeon_get_vblank_counter_kms] crtc 0: dist from vblank start 3 > >>> [drm:drm_update_vblank_count] updating vblank count on crtc 0: current=218104694, diff=16776301, hw=1 hw_last=916 > >> > >> Not sure what bug we're talking about here, but here the hw counter > >> clearly jumps backwards. > >> > >>> [drm:radeon_get_vblank_counter_kms] Query failed! stat 3 > >>> [drm:radeon_get_vblank_counter_kms] Query failed! stat 3 > >>> [drm:drm_update_vblank_count] updating vblank count on crtc 1: current=0, diff=0, hw=0 hw_last=0 > >>> [drm:radeon_get_vblank_counter_kms] Query failed! stat 3 > >>> [drm:radeon_get_vblank_counter_kms] Query failed! stat 3 > >>> [drm:drm_update_vblank_count] updating vblank count on crtc 2: current=0, diff=0, hw=0 hw_last=0 > >>> [drm:radeon_get_vblank_counter_kms] Query failed! stat 3 > >>> [drm:radeon_get_vblank_counter_kms] Query failed! stat 3 > >>> [drm:drm_update_vblank_count] updating vblank count on crtc 3: current=0, diff=0, hw=0 hw_last=0 > >>> [drm:radeon_get_vblank_counter_kms] Query failed! stat 1 > >>> [drm:drm_calc_vbltimestamp_from_scanoutpos] crtc 0 : v 0x1 p(0,0)@ 7304.317140 -> 7304.317140 [e 0 us, 0 rep] > >>> [drm:radeon_get_vblank_counter_kms] Query failed! stat 1 > >>> [drm:drm_update_vblank_count] updating vblank count on crtc 0: current=234880995, diff=16777215, hw=0 hw_last=1 > >> > >> Same here. > > > > At least one of the jumps is expected, because this is around turning > > off the CRTC for DPMS off. Don't know yet why there are two jumps back > > though. > > > > > >> These things just don't happen on i915 because drm_vblank_off() and > >> drm_vblank_on() are always called around the times when the hw counter > >> might get reset. Or at least that's how it should be. > > > > Which is of course the idea of Daniel's patch (which is what I'm getting > > the above with) or Mario's patch as well, but clearly something's still > > wrong. It's certainly possible that it's something in the driver, but > > since calling drm_vblank_pre/post_modeset from the same places seems to > > work fine (ignoring the regression discussed in this thread)... Do > > drm_vblank_on/off require something else to handle this correctly? > > > > > > I suspect it is because vblank_disable_and_save calls > drm_update_vblank_count() unconditionally, even if vblank irqs are > already off. > > So on a manual display disable -> reenable you get something like > > At disable: > > Call to dpms-off --> atombios_crtc_dpms(DPMS_OFF) --> drm_vblank_off -> > vblank_disable_and_save -> irqs off, drm_update_vblank_count() computes > final count. > > Then the crtc is shut down and its hw counter resets to zero. > > At reenable: > > Modesetting -> drm_crtc_helper_set_mode -> crtc_funcs->prepare(crtc) -> > atombios_crtc_prepare() -> atombios_crtc_dpms(DPMS_OFF) -> > drm_vblank_off -> vblank_disable_and_save -> A pointless > drm_update_vblank_count() while the hw counter is already reset to zero > --> Unwanted counter jump. > > > The problem doesn't happen on a pure modeset to a different video > resolution/refresh rate, as then we only have one call into > atombios_crtc_dpms(DPMS_OFF). > > I think the fix is to fix vblank_disable_and_save() to only call > drm_update_vblank_count() if vblank irqs get actually disabled, not on > no-op calls. I will try that now. It does that on purpose. Otherwise the vblank counter would appear to have stalled while the interrupt was off. > > Otherwise kms drivers would have to be careful to never call > drm_vblank_off multiple times before calling drm_vblank_on, but the help > text to drm_vblank_on() claims that unbalanced calls to these functions > are perfectly fine. > > -mario > > > > > > > -- Ville Syrjälä Intel OTC _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/dri-devel
