On 5/6/24 03:35, Laurent Pinchart wrote: > On Mon, May 06, 2024 at 09:29:36AM +0200, Maxime Ripard wrote: >> Hi Laurent, Sean, >> >> On Sat, May 04, 2024 at 03:21:18PM GMT, Laurent Pinchart wrote: >> > On Fri, May 03, 2024 at 05:54:32PM -0400, Sean Anderson wrote: >> > > I have discovered a bug in the displayport driver on drm-misc-next. To >> > > trigger it, run >> > > >> > > echo fd4a0000.display > /sys/bus/platform/drivers/zynqmp-dpsub/unbind >> > > >> > > The system will become unresponsive and (after a bit) splat with a hard >> > > LOCKUP. One core will be unresponsive at the first zynqmp_dp_read in >> > > zynqmp_dp_bridge_detect. >> > > >> > > I believe the issue is due the registers being unmapped and the block >> > > put into reset in zynqmp_dp_remove instead of zynqmp_dpsub_release. >> > >> > That is on purpose. Drivers are not allowed to access the device at all >> > after .remove() returns. >> >> It's not "on purpose" no. Drivers indeed are not allowed to access the >> device after remove, but the kernel shouldn't crash. This is exactly >> why we have drm_dev_enter / drm_dev_exit. > > I didn't mean the crash was on purpose :-) It's the registers being > unmapped that is, as nothing should touch those registers after > .remove() returns. OK, so then we need to have some kind of flag in the driver or in the drm subsystem so we know not to access those registers. --Sean
