linux-kernel - RE: [PATCH] cpufreq: amd-pstate: Don't create attributes when registration fails

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Date: Mon, 24 Jun 2024 03:32:21 +0000
From: "Yuan, Perry" <Perry.Yuan@....com>
To: "Limonciello, Mario" <Mario.Limonciello@....com>, "Shenoy, Gautham Ranjal"
	<gautham.shenoy@....com>
CC: "linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"alex.s.cochran@...ton.me" <alex.s.cochran@...ton.me>, Peter Jung
	<peterjung1337@...il.com>
Subject: RE: [PATCH] cpufreq: amd-pstate: Don't create attributes when
 registration fails

[AMD Official Use Only - AMD Internal Distribution Only]

Hi Mario,

> -----Original Message-----
> From: Limonciello, Mario <Mario.Limonciello@....com>
> Sent: Monday, June 24, 2024 4:09 AM
> To: Yuan, Perry <Perry.Yuan@....com>; Shenoy, Gautham Ranjal
> <gautham.shenoy@....com>
> Cc: linux-pm@...r.kernel.org; linux-kernel@...r.kernel.org; Limonciello,
> Mario <Mario.Limonciello@....com>; alex.s.cochran@...ton.me; Peter
> Jung <peterjung1337@...il.com>
> Subject: [PATCH] cpufreq: amd-pstate: Don't create attributes when
> registration fails
>
> If driver registration fails then immediately return the failure instead of
> continuing to register attributes.
>
> This fixes issues of falling back from amd-pstate to other drivers when
> cpufreq init has failed for any reason.
>
> Reported-by: alex.s.cochran@...ton.me
> Signed-off-by: Mario Limonciello <mario.limonciello@....com>
> ---
> Cc: Peter Jung <peterjung1337@...il.com>  drivers/cpufreq/amd-pstate.c |
> 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
> index 05e80d2f8803..7195dfa98cc5 100644
> --- a/drivers/cpufreq/amd-pstate.c
> +++ b/drivers/cpufreq/amd-pstate.c
> @@ -2030,8 +2030,10 @@ static int __init amd_pstate_init(void)
>       }
>
>       ret = cpufreq_register_driver(current_pstate_driver);
> -     if (ret)
> +     if (ret) {
>               pr_err("failed to register with return %d\n", ret);
> +             goto disable_driver;
> +     }
>
>       dev_root = bus_get_dev_root(&cpu_subsys);
>       if (dev_root) {
> @@ -2047,6 +2049,8 @@ static int __init amd_pstate_init(void)
>
>  global_attr_free:
>       cpufreq_unregister_driver(current_pstate_driver);
> +disable_driver:
> +     amd_pstate_enable(false);
>       return ret;
>  }
>  device_initcall(amd_pstate_init);
> --
> 2.43.0


In the previous failure behavior, I saw most of time, the driver will fallback to acpi_cpufreq driver when pstate driver failed to load.
I agree to disable it explicitly with this patch.

Reviewed-by: Perry Yuan <Perry.Yuan@....com>