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

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Message-ID: <CAKb7UvhyCVoFXYL74eX3rXtt=V7nOnBGaTPVdcJT37v38jD8oQ@mail.gmail.com>
Date:   Tue, 30 Aug 2016 11:44:38 -0400
From:   Ilia Mirkin <imirkin@...m.mit.edu>
To:     Roland Singer <roland.singer@...ertbit.com>
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

On Tue, Aug 30, 2016 at 11:25 AM, Roland Singer
<roland.singer@...ertbit.com> wrote:
> I tried these scenarios:
>
> 1. Booted the system without the bbswitch module. The nouveau module
>    was loaded and is responsible for the power management of the GPU.
>    The graphical session freezes after some minutes...
>
> 2. Booted the system without bbswitch and with nouveau blacklisted.
>    Manually loaded bbswitch to switch off the discrete GPU.
>    Same freeze after a while or by explicitly obtaining the GPU state.
>
> Is there a possibility to switch off the discrete card without bbswitch?
> If this is possible, then I could test this without nouveau and bbswitch
> at all. If the system hangs, then it is not the video driver nor bbswitch.

You can use acpi_call (a random search points to
https://github.com/mkottman/acpi_call, but I don't know if that's the
"official" version) - need to find the right method to call, but
that's basically all it takes to acpi-suspend a gpu.

Separately, there was a recent fix to ... something, including but not
limited to nouveau, involving hangs on gpu suspend on newer laptops. I
don't think it's upstream yet. Look for patches from Lukas Wunner.

  -ilia