linux-kernel - Re: [PATCH v4 10/11] cpufreq: amd-pstate: auto-load pstate driver by default

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Date: Tue, 18 Jun 2024 14:25:25 -0500
From: Mario Limonciello <mario.limonciello@....com>
To: Perry Yuan <perry.yuan@....com>, rafael.j.wysocki@...el.com,
 viresh.kumar@...aro.org, Ray.Huang@....com, gautham.shenoy@....com,
 Borislav.Petkov@....com
Cc: Alexander.Deucher@....com, Xinmei.Huang@....com, Xiaojian.Du@....com,
 Li.Meng@....com, linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 10/11] cpufreq: amd-pstate: auto-load pstate driver by
 default

On 6/17/2024 01:59, Perry Yuan wrote:
> If the `amd-pstate` driver is not loaded automatically by default,
> it is because the kernel command line parameter has not been added.
> To resolve this issue, it is necessary to call the `amd_pstate_set_driver()`
> function to enable the desired mode (passive/active/guided) before registering
> the driver instance.
> 
> This ensures that the driver is loaded correctly without relying on the kernel
> command line parameter.
> 
> When there is no parameter added to command line, Kernel config will
> provide the default mode to load.
> 
> Meanwhle, user can add driver mode in command line which will override

Meanwhile

> the kernel config default option.

I think you'll probably want to swap the order of patch 10 and patch 11.

> 
> Reported-by: Andrei Amuraritei <andamu@...teo.net>
> Closes: https://bugzilla.kernel.org/show_bug.cgi?id=218705
> Signed-off-by: Perry Yuan <perry.yuan@....com>

Reviewed-by: Mario Limonciello <mario.limonciello@....com>

> ---
>   drivers/cpufreq/amd-pstate.c | 24 +++++++++++++++++-------
>   1 file changed, 17 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
> index cf68343219d1..b48fd60cbc6d 100644
> --- a/drivers/cpufreq/amd-pstate.c
> +++ b/drivers/cpufreq/amd-pstate.c
> @@ -1857,8 +1857,13 @@ static int __init amd_pstate_init(void)
>   	/* check if this machine need CPPC quirks */
>   	dmi_check_system(amd_pstate_quirks_table);
>   
> -	switch (cppc_state) {
> -	case AMD_PSTATE_UNDEFINED:
> +	/*
> +	* determine the driver mode from the command line or kernel config.
> +	* If no command line input is provided, cppc_state will be AMD_PSTATE_UNDEFINED.
> +	* command line options will override the kernel config settings.
> +	*/
> +
> +	if (cppc_state == AMD_PSTATE_UNDEFINED) {
>   		/* Disable on the following configs by default:
>   		 * 1. Undefined platforms
>   		 * 2. Server platforms
> @@ -1870,15 +1875,20 @@ static int __init amd_pstate_init(void)
>   			pr_info("driver load is disabled, boot with specific mode to enable this\n");
>   			return -ENODEV;
>   		}
> -		ret = amd_pstate_set_driver(CONFIG_X86_AMD_PSTATE_DEFAULT_MODE);
> -		if (ret)
> -			return ret;
> -		break;
> +		/* get driver mode from kernel config option [1:4] */
> +		cppc_state = CONFIG_X86_AMD_PSTATE_DEFAULT_MODE;
> +	}
> +
> +	switch (cppc_state) {
>   	case AMD_PSTATE_DISABLE:
> +		pr_info("driver load is disabled, boot with specific mode to enable this\n");
>   		return -ENODEV;
>   	case AMD_PSTATE_PASSIVE:
>   	case AMD_PSTATE_ACTIVE:
>   	case AMD_PSTATE_GUIDED:
> +		ret = amd_pstate_set_driver(cppc_state);
> +		if (ret)
> +			return ret;
>   		break;
>   	default:
>   		return -EINVAL;
> @@ -1899,7 +1909,7 @@ static int __init amd_pstate_init(void)
>   	/* enable amd pstate feature */
>   	ret = amd_pstate_enable(true);
>   	if (ret) {
> -		pr_err("failed to enable with return %d\n", ret);
> +		pr_err("failed to enable driver mode(%d)\n", cppc_state);
>   		return ret;
>   	}
>