Hi, after resuming from suspend nouveau starts writing Failed to idle channel x (where x is 2 or 3) to the log and X appears to stop and then restart only to stop again. Starting Firefox after resuming triggers the bugs every time, and bisecting leads to 03bd6efa ("drm/nv50/fifo: use hardware channel kickoff functionality").
$ grep -i nouveau .config CONFIG_DRM_NOUVEAU=y CONFIG_DRM_NOUVEAU_BACKLIGHT=y # CONFIG_DRM_NOUVEAU_DEBUG is not set
Relevant part of the log (running v3.5-rc2-15-g4e3c8a1): [ 79.040710] PM: resume of devices complete after 1952.375 msecs [ 79.041735] PM: Finishing wakeup. [ 79.064052] Restarting tasks ... done. [ 79.064064] video LNXVIDEO:00: Restoring backlight state [ 79.645442] tg3 0000:09:00.0: irq 47 for MSI/MSI-X [ 79.707851] IPv6: ADDRCONF(NETDEV_UP): p3p1: link is not ready [ 81.288510] tg3 0000:09:00.0: p3p1: Link is up at 100 Mbps, full duplex [ 81.288510] tg3 0000:09:00.0: p3p1: Flow control is on for TX and on for RX [ 81.289824] IPv6: ADDRCONF(NETDEV_CHANGE): p3p1: link becomes ready [ 376.646417] [drm] nouveau 0000:01:00.0: PFIFO: channel 4 unload timeout [ 378.649010] [sched_delayed] sched: RT throttling activated [ 384.677024] [drm] nouveau 0000:01:00.0: Failed to idle channel 2. [ 384.678012] [drm] nouveau 0000:01:00.0: PFIFO: channel 2 unload timeout [ 389.685024] [drm] nouveau 0000:01:00.0: Failed to idle channel 3. [ 389.686012] [drm] nouveau 0000:01:00.0: PFIFO: channel 3 unload timeout [ 401.534024] [drm] nouveau 0000:01:00.0: Failed to idle channel 2. [ 401.535012] [drm] nouveau 0000:01:00.0: PFIFO: channel 2 unload timeout ... [ 456.688024] [drm] nouveau 0000:01:00.0: Failed to idle channel 3. [ 456.689013] [drm] nouveau 0000:01:00.0: PFIFO: channel 3 unload timeout [ 468.372025] [drm] nouveau 0000:01:00.0: Failed to idle channel 2. [ 468.373013] [drm] nouveau 0000:01:00.0: PFIFO: channel 2 unload timeout