linux-kernel - Re: Kernel Freeze with American Megatrends BIOS

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Message-ID: <98b2ae5b-399b-8337-18dc-98ac2480746f@desertbit.com>
Date:   Wed, 31 Aug 2016 13:12:30 +0200
From:   Roland Singer <roland.singer@...ertbit.com>
To:     Peter Wu <peter@...ensteyn.nl>, Ilia Mirkin <imirkin@...m.mit.edu>
Cc:     Emil Velikov <emil.l.velikov@...il.com>,
        Bjorn Helgaas <helgaas@...nel.org>,
        Linux PCI <linux-pci@...r.kernel.org>,
        "Linux-Kernel@...r. Kernel. Org" <linux-kernel@...r.kernel.org>,
        ML dri-devel <dri-devel@...ts.freedesktop.org>,
        "linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>
Subject: Re: Kernel Freeze with American Megatrends BIOS

Am 30.08.2016 um 21:21 schrieb Peter Wu:
> On Tue, Aug 30, 2016 at 02:13:46PM -0400, Ilia Mirkin wrote:
>> On Tue, Aug 30, 2016 at 2:02 PM, Roland Singer
>> <roland.singer@...ertbit.com> wrote:
>>> I configured bbswitch to not set any states automatically...
>>> So it's possible to obtain and verify the GPU power state.
>>>
>>> However I removed the bbswitch module and booted with nouveau.
>>>
>>> Kernel 4.7.2: nouveau switches the discrete GPU off.
>>>               I can't trigger the freeze, because bbswitch is missing.
>>>               I'll work with the system and see if it will freeze.
>>>
>>> Kernel 4.8-rc4: nouveau does not care about the power state and
>>>                 the discrete GPU is never switched off. I will notice
>>>                 this, because the second cooling FAN will stop...
>>>                 Same log messages as send before.
>>
>> That's surprising. I believe there's an issue with the new logic when
>> there's an HDMI audio subdevice. However that only appears if there's
>> a cable plugged in, at least in the systems Peter tested. You should
>> be able to see whether it's there or not with 'lspci'.
> 
> I doubt that the audio device is responsible here, that should only show
> up after following very specific steps (runtime suspend/resume (PCI or
> ACPI magic), remove PCI device, rescan bus).
> 
>> You can check for sure by looking in the vgaswitcheroo state. It
>> should say DynOff when it's powered off.
>>
>> Either way, I think using bbswitch + nouveau isn't supported by
>> anyone, so if you want to use it that way, you're on your own. (You
>> may want to load nouveau with runpm=0 so that nouveau doesn't try to
>> manage the GPU suspend stuff.)
> 
> I understood that Roland's intent is to check the power state, not use
> the suspend functionality of bbswitch, if you load bbswitch without
> module options amd do not write to /proc/bbswitch, then it allows you to
> read out the actual status (you could also just use lspci -H1 for that
> though).
> 

lspci -H1 works perfect. Thanks.
Just tried to verify the output with lspci -H1. I unloaded the nouveau
module and modprobe freezed with:

  $ modprobe -r nouveau
    nouveau 0000:01:00.0: pci: failed to adjust lnkctl speed
    nouveau 0000:01:00.0: fb: init failed. -22
    nouveau 0000:01:00.0: init failed with -22
    nouveau: DRM:00000000:00000000: init failed with -22
    nouveau: DRM:00000000:00000000: init failed with -22