On Fri, Feb 2, 2018 at 7:18 PM, Andy Lutomirski <luto@xxxxxxxxxx> wrote: > 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. I filed https://bugs.freedesktop.org/show_bug.cgi?id=104931 for the questionable reactivation logic issue. If nothing else, I doubt that the reactivation timeout logic does what its author intended for it to do. --Andy _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/intel-gfx
