linux-kernel - Re: [PATCH] fix linux 5.16 freeze regression on 32-bit ThinkPad T40

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Date:   Wed, 16 Feb 2022 18:20:31 +0100
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Hans de Goede <hdegoede@...hat.com>,
        Woody Suwalski <wsuwalski@...il.com>
Cc:     Linux PM <linux-pm@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>
Subject: Re: [PATCH] fix linux 5.16 freeze regression on 32-bit ThinkPad T40

On Mon, Feb 14, 2022 at 12:32 PM Hans de Goede <hdegoede@...hat.com> wrote:
>
> Hi,
>
> On 2/9/22 22:05, Woody Suwalski wrote:
> > From: Woody Suwalski <wsuwalski@...il.com>
> >
> > Add and ACPI idle power level limit for 32-bit ThinkPad T40.
> >
> > There is a regression on T40 introduced by commit d6b88ce2, starting with kernel 5.16:
> >
> > commit d6b88ce2eb9d2698eb24451eb92c0a1649b17bb1
> > Author: Richard Gong <richard.gong@....com>
> > Date:   Wed Sep 22 08:31:16 2021 -0500
> >
> >     ACPI: processor idle: Allow playing dead in C3 state
> >
> > The above patch is trying to enter C3 state during init, what is causing a T40 system freeze. I have not found a similar issue on any other of my 32-bit machines.
> >
> > The fix is to add another exception to the processor_power_dmi_table[] list.
> > As a result the dmesg shows as expected:
> >
> >     2.155398] ACPI: IBM ThinkPad T40 detected - limiting to C2 max_cstate. Override with "processor.max_cstate=9"
> > [    2.155404] ACPI: processor limited to max C-state 2
> >
> > The fix is trivial and affects only vintage T40 systems.
> >
> > Signed-off-by: Woody Suwalski <wsuwalski@...il.com>
> > ---
>
> Thanks, patch looks good to me:
>
> Reviewed-by: Hans de Goede <hdegoede@...hat.com>
>
> Regards,
>
> Hans
>
>
> > --- a/drivers/acpi/processor_idle.c    2022-02-04 09:09:54.515906362 -0500
> > +++ b/drivers/acpi/processor_idle.c    2022-02-04 14:21:08.264911271 -0500
> > @@ -96,6 +96,11 @@ static const struct dmi_system_id proces
> >        DMI_MATCH(DMI_SYS_VENDOR, "ASUSTeK Computer Inc."),
> >        DMI_MATCH(DMI_PRODUCT_NAME,"L8400B series Notebook PC")},
> >       (void *)1},
> > +    /* T40 can not handle C3 idle state */
> > +    { set_max_cstate, "IBM ThinkPad T40", {
> > +      DMI_MATCH(DMI_SYS_VENDOR, "IBM"),
> > +      DMI_MATCH(DMI_PRODUCT_NAME, "23737CU")},
> > +     (void *)2},
> >      {},
> >  };

Applied as a fix for 5.17-rc5, thanks!