Hi Doug, On Mon, Apr 28, 2025 at 01:40:25PM -0700, Doug Anderson wrote: > On Sun, Apr 20, 2025 at 9:26■PM Nick Bowler <nbow...@draconx.ca> wrote: > > I recently noticed that on current kernels I lose video output from > > my Blackbird's AST2500 BMC after a reboot [...] > > ce3d99c8349584bc0fbe1e21918a3ea1155343aa is the first bad commit > > commit ce3d99c8349584bc0fbe1e21918a3ea1155343aa > > Author: Douglas Anderson <diand...@chromium.org> > > Date: Fri Sep 1 16:39:53 2023 -0700 > > > > drm: Call drm_atomic_helper_shutdown() at shutdown time for misc > > drivers [...] > Bleh. That's not good. If I had to guess there's some subtle bug / > missing timing constraint that's being triggered here. A few things to > try: > > 1. Add a several second delay after the call to > "drm_atomic_helper_shutdown()", like msleep(5000) or something like > that. That's kind of a shot in the dark, but it's fairly common for > panels to get upset if you turn them off and then turn them on again > too quickly. This would be my blind guess of what is happening.
Adding msleep(5000) does nothing except that once the video turns off it now takes 5 seconds longer to reboot. > 2. Could you give more details about what panel you're using? According to the documentation I have for the machine, the video output of the AST2500 BMC is connected to an IT66121 HDMI transmitter. Then in turn I have that connected to some generic HDMI->VGA adapter (PrimeCables branded). I also tried with another much more expensive device (Extron DVI-RGB 200) and observe no difference in behaviour. i think these devices are working and there's just no output signal on the hdmi port. > Ideally it'd be great if you could say which device tree you're using too. Not sure how to answer this. Do you want me to look at something specific in /proc/device-tree? Or dump it somehow? > 3. Any chance you can gather the `dmesg` from a failing boot and > provide it somehow? Are there any errors in the logs from the failing > boot? To clarify, there is no boot failure. There is just no video output after rebooting. I can then boot Linux again by any method that works without being able to see the screen, and then everything is fine once I do that. I've attached the dmesg output (gzipped) from after such a reboot. Except for the order and the timestamps, the messages are identical to when I boot after rebooting a kernel which does not disable the video. Thanks, Nick
boot-novid.log.gz
Description: application/gzip
