linux-kernel - Re: [PATCH v5 8/8] cpufreq: amd-pstate: auto-load pstate driver by default

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Date: Fri, 21 Jun 2024 14:11:13 +0530
From: Gautham R.Shenoy <gautham.shenoy@....com>
To: Perry Yuan <perry.yuan@....com>, <Mario.Limonciello@....com>
CC: <rafael.j.wysocki@...el.com>, <viresh.kumar@...aro.org>,
	<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 v5 8/8] cpufreq: amd-pstate: auto-load pstate driver by
 default

Perry Yuan <perry.yuan@....com> writes:

> 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.
>
> Meanwhile, user can add driver mode in command line which will override
> the kernel config default option.
>
> 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>

Reviewed-by: Gautham R. Shenoy <gautham.shenoy@....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 0f8ffbc0dc2a..a96ad7d10a4d 100644
> --- a/drivers/cpufreq/amd-pstate.c
> +++ b/drivers/cpufreq/amd-pstate.c
> @@ -1801,8 +1801,13 @@ 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
> @@ -1812,15 +1817,20 @@ 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;
> @@ -1841,7 +1851,7 @@ 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;
>  	}
>  
> -- 
> 2.34.1