On Fri, Feb 2, 2018 at 1:24 AM, Andy Lutomirski <luto@xxxxxxxxxx> wrote: > On Thu, Feb 1, 2018 at 9:20 PM, Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> wrote: >> Quoting Andy Lutomirski (2018-02-01 21:04:30) >>> I got this after a recent suspend/resume: >>> >>> Feb 01 09:44:34 laptop systemd-logind[2412]: Lid closed. >>> Feb 01 09:44:34 laptop systemd-logind[2412]: device-enumerator: scan all dirs >>> Feb 01 09:44:34 laptop systemd-logind[2412]: device-enumerator: >>> scanning /sys/bus >>> Feb 01 09:44:34 laptop systemd-logind[2412]: device-enumerator: >>> scanning /sys/class >>> Feb 01 09:44:34 laptop systemd-logind[2412]: Failed to open >>> configuration file '/etc/systemd/sleep.conf': No such file or >>> directory >>> Feb 01 09:44:34 laptop systemd-logind[2412]: Suspending... >>> Feb 01 09:44:34 laptop systemd-logind[2412]: Sent message type=signal >>> sender=n/a destination=n/a object=/org/freedesktop/login1 >>> interface=org.freedesktop.login1.Manager member=PrepareForSleep >>> cookie=570 reply >>> Feb 01 09:44:34 laptop systemd-logind[2412]: Got message >>> type=method_call sender=:1.46 destination=:1.1 >>> object=/org/freedesktop/login1/session/_32 >>> interface=org.freedesktop.login1.Session member=ReleaseDevice >>> Feb 01 09:44:34 laptop systemd-logind[2412]: Sent message type=signal >>> sender=n/a destination=:1.46 >>> object=/org/freedesktop/login1/session/_32 >>> interface=org.freedesktop.login1.Session member=PauseDevice cookie >>> Feb 01 09:44:34 laptop gnome-shell[2630]: Failed to apply DRM plane >>> transform 0: Permission denied >>> Feb 01 09:44:34 laptop gnome-shell[2630]: drmModeSetCursor2 failed >>> with (Permission denied), drawing cursor with OpenGL from now on >>> >>> But I don't see the word "cursor" in my system logs before the first >>> suspend. What am I looking for? This is Fedora 27 running a Gnome >>> Wayland session, but it hasn't been reinstalled in some time, so it's >>> possible that there are some weird settings sitting around. But I did >>> check and I have no weird i915 parameters. >> >> You are using gnome-shell as the display server. From that it appears to >> have started off with a HW cursor and switched to a SW cursor after >> suspend. Did you notice a change in behaviour? After rebooting or just >> restarting gnome-shell? > > I think it's less consistently bad after a reboot before suspending. > >> >>> Also, are these things potentially related: >>> >>> [ 3067.702527] [drm:intel_pipe_update_start [i915]] *ERROR* Potential >>> atomic update failure on pipe A >> >> They are just "missed the immediate vblank for the screen update" >> messages. Should not be related to PSR, but may cause jitter by delaying >> the odd screen update. > > I just got this one, and the timestamp is at least reasonably close to > a giant latency spike: > > [ 288.799654] [drm:intel_pipe_update_end [i915]] *ERROR* Atomic > update failure on pipe A (start=31 end=32) time 15 us, min 1073, max > 1079, scanline start 1087, end 1088 > >> >>> As I'm typing this, I've seen a couple instances of what seems like a >>> full *second* of cursor latency, but I've only gotten the potential >>> atomic update failure once. >>> >>> And is there any straightforward tracing to do to distinguish between >>> PSR exit latency and other potential sources of latency? >> >> It looks plausible that we could at least report how long it takes the >> registers to reflect the change in state (but we don't). The best source >> of information atm is /sys/kernel/debug/dri/0/i915_edp_psr_status. > > Hmm. > > I went and looked at the code, and I noticed what could be bugs or > could (more likely) be my confusion since I don't know this code at > all: > > intel_single_frame_update() does something inscrutable to me, but I > imagine it does something that causes the next page flip to get > noticed by the panel even with PSR on. But how does the code that > calls it know that anything happened? (Looking at the commit history, > maybe this is something special that's only needed on some platforms > but doesn't replace the normal PSR exit sequence.) > > Perhaps more interestingly, intel_psr_flush() does this: > > /* By definition flush = invalidate + flush */ > if (frontbuffer_bits) > intel_psr_exit(dev_priv); > > if (!dev_priv->psr.active && !dev_priv->psr.busy_frontbuffer_bits) > if (!work_busy(&dev_priv->psr.work.work)) > schedule_delayed_work(&dev_priv->psr.work, > msecs_to_jiffies(100)); > > I'm guessing that the idea is that we're turning off PSR because we > want the panel to update and we expect that, in 100ms, the update will > have hit the panel and we'll have been idle long enough for it to make > sense to re-enter PSR. IOW, the code wants PSR to be off for at least > 100ms and then to turn back on. But this code actually says "turn PSR > back on in at *most* 100ms". What happens if there are two screen > updates 99ms apart? The first one should work fine, but the next one > will hit with 1ms left on the delayed work, and intel_psr_work() will > get called in 1ms. There's some magic with busy_frontbuffer_bits, but > it seems questionable to me that intel_psr_flush() clears > busy_frontbuffer_bits and *then* calls intel_psr_exit(). > > Naively, I would expect that PSR needs to be kept off until the vblank > following the page flip. > > Also, in intel_psr_work(), shouldn't this code: > > /* > * The delayed work can race with an invalidate hence we need to > * recheck. Since psr_flush first clears this and then reschedules we > * won't ever miss a flush when bailing out here. > */ > if (dev_priv->psr.busy_frontbuffer_bits) > goto unlock; > > re-arm the delayed work? > > Anyway, this is all on a 4.14 kernel. I should update to 4.16 and see > what happens. I updated to 4.15, and the situation is much worse. With enable_psr=1, the system survives for several seconds and then the screen stops updating entirely. If I boot with i915.enable_psr=1, I get to the Fedora login screen and then the system dies. If I set enable_psr=1 using sysfs, it does a bit after the next resume. It seems like it also sometimes hangs even worse a bit after the screen stops updating, but it's hard to tell. I see this in my logs: [drm:drm_atomic_helper_wait_for_flip_done [drm_kms_helper]] *ERROR* [CRTC:37:pipe A] flip_done timed out Sometimes I see this a bit later: [drm:drm_atomic_helper_wait_for_dependencies [drm_kms_helper]] *ERROR* [CRTC:37:pipe A] flip_done timed out I'm able to get some debugging out before the system dies. I see intel_psr_flush() getting called a bunch, and I don't see intel_psr_invalidate() being called at all. I also see intel_psr_work() activating psr as little as 2ms after intel_psr_flush() finishes. So I think the code is indeed buggy or at least questionable. I'd try to fix it (at least as well as I can without knowing anything about how the PSR state machine actually works), but the fact that the system hangs would make it very hard to test. _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
