Date:   Tue, 31 Jan 2023 09:27:54 +1000
From:   Ben Skeggs <skeggsb@...il.com>
To:     Chris Clayton <chris2553@...glemail.com>
Cc:     Linux regressions mailing list <regressions@...ts.linux.dev>,
        bskeggs@...hat.com, Karol Herbst <kherbst@...hat.com>,
        Lyude Paul <lyude@...hat.com>,
        ML nouveau <nouveau@...ts.freedesktop.org>,
        LKML <linux-kernel@...r.kernel.org>,
        ML dri-devel <dri-devel@...ts.freedesktop.org>
Subject: Re: linux-6.2-rc4+ hangs on poweroff/reboot: Bisected

On Tue, 31 Jan 2023 at 09:09, Chris Clayton <chris2553@...glemail.com> wrote:
>
> Hi again.
>
> On 30/01/2023 20:19, Chris Clayton wrote:
> > Thanks, Ben.
>
> <snip>
>
> >> Hey,
> >>
> >> This is a complete shot-in-the-dark, as I don't see this behaviour on
> >> *any* of my boards.  Could you try the attached patch please?
> >
> > Unfortunately, the patch made no difference.
> >
> > I've been looking at how the graphics on my laptop is set up, and have a bit of a worry about whether the firmware might
> > be playing a part in this problem. In order to offload video decoding to the NVidia TU117 GPU, it seems the scrubber
> > firmware must be available, but as far as I know,that has not been released by NVidia. To get it to work, I followed
> > what ubuntu have done and the scrubber in /lib/firmware/nvidia/tu117/nvdec/ is a symlink to
> > ../../tu116/nvdev/scrubber.bin. That, of course, means that some of the firmware loaded is for a different card is being
> > loaded. I note that processing related to firmware is being changed in the patch. Might my set up be at the root of my
> > problem?
> >
> > I'll have a fiddle an see what I can work out.
> >
> > Chris
> >
> >>
> >> Thanks,
> >> Ben.
> >>
> >>>
>
> Well, my fiddling has got my system rebooting and shutting down successfully again. I found that if I delete the symlink
> to the scrubber firmware, reboot and shutdown work again. There are however, a number of other files in the tu117
> firmware directory tree that that are symlinks to actual files in its tu116 counterpart. So I deleted all of those too.
> Unfortunately, the absence of one or more of those symlinks causes Xorg to fail to start. I've reinstated all the links
> except scrubber and I now have a system that works as it did until I tried to run a kernel that includes the bad commit
> I identified in my bisection. That includes offloading video decoding to the NVidia card, so what ever I read that said
> the scrubber firmware was needed seems to have been wrong. I get a new message that (nouveau 0000:01:00.0: fb: VPR
> locked, but no scrubber binary!), but, hey, we can't have everything.
>
> If you still want to get to the bottom of this, let me know what you need me to provide and I'll do my best. I suspect
> you might want to because there will a n awful lot of Ubuntu-based systems out there with that scrubber.bin symlink in
> place. On the other hand,m it could but quite a while before ubuntu are deploying 6.2 or later kernels.
The symlinks are correct - whole groups of GPUs share the same FW, and
we use symlinks in linux-firmware to represent this.

I don't really have any ideas how/why this patch causes issues with
shutdown - it's a path that only gets executed during initialisation.
Can you try and capture the kernel log during shutdown ("dmesg -w"
over ssh? netconsole?), and see if there's any relevant messages
providing a hint at what's going on?  Alternatively, you could try
unloading the module (you will have to stop X/wayland/gdm/etc/etc
first) and seeing if that hangs too.

Ben.

>
> Thanks,
>
> Chris
>
> <snip>

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