linux-kernel - Re: [PATCH 11/12] cpufreq: amd-pstate: add ACPI disabled check

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Date:   Thu, 7 Jul 2022 14:46:11 -0500
From:   Nathan Fontenot <nafonten@....com>
To:     Perry Yuan <Perry.Yuan@....com>, rafael.j.wysocki@...el.com,
        viresh.kumar@...aro.org, Ray.Huang@....com,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Len Brown <lenb@...nel.org>, linux-acpi@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org
Cc:     Deepak.Sharma@....com, Mario.Limonciello@....com,
        Nathan.Fontenot@....com, Alexander.Deucher@....com,
        Jinzhou.Su@....com, Xinmei.Huang@....com, Xiaojian.Du@....com,
        Li.Meng@....com
Subject: Re: [PATCH 11/12] cpufreq: amd-pstate: add ACPI disabled check

On 7/7/22 12:01, Perry Yuan wrote:
> Add acpi function check in case ACPI is not enabled, that will cause
> pstate driver failed to call cppc acpi to change perf or update epp
> value for shared memory solution processors.
> 
> When CPPC is invalid, warning log will be needed to be printed to tell
> user what is wrong.
> 
> Signed-off-by: Perry Yuan <Perry.Yuan@....com>
> ---
>  drivers/acpi/cppc_acpi.c     | 3 +++
>  drivers/cpufreq/amd-pstate.c | 2 +-
>  2 files changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/acpi/cppc_acpi.c b/drivers/acpi/cppc_acpi.c
> index 6ff1901d7d43..17d67e3ededf 100644
> --- a/drivers/acpi/cppc_acpi.c
> +++ b/drivers/acpi/cppc_acpi.c
> @@ -424,6 +424,9 @@ bool acpi_cpc_valid(void)
>  	struct cpc_desc *cpc_ptr;
>  	int cpu;
>  
> +	if (acpi_disabled)
> +		return false> +

This seems ok, the only other places I find that call acpi_cpc_valid() also check
for acpi_disabled.

If the acpi_disabled check is added to acpi_cpc_valid() the other calling sites should
be updated to remove their check for acpi_disabled.

-Nathan

>  	for_each_present_cpu(cpu) {
>  		cpc_ptr = per_cpu(cpc_desc_ptr, cpu);
>  		if (!cpc_ptr)
> diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
> index b54b3b559993..6d81a9a94dde 100644
> --- a/drivers/cpufreq/amd-pstate.c
> +++ b/drivers/cpufreq/amd-pstate.c
> @@ -684,7 +684,7 @@ static int __init amd_pstate_init(void)
>  		return -ENODEV;
>  
>  	if (!acpi_cpc_valid()) {
> -		pr_debug("the _CPC object is not present in SBIOS\n");
> +		pr_warn_once("the _CPC object is not present in SBIOS or ACPI disabled\n");
>  		return -ENODEV;
>  	}
>