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

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Date:   Mon, 14 Feb 2022 12:13:02 +0100
From:   Hans de Goede <hdegoede@...hat.com>
To:     Woody Suwalski <wsuwalski@...il.com>, 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

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},
>      {},
>  };
> 
>