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Date:   Tue, 17 Jan 2023 19:57:12 +0800
From:   Huang Rui <ray.huang@amd.com>
To:     "Yuan, Perry" <Perry.Yuan@amd.com>
Cc:     "rafael.j.wysocki@intel.com" <rafael.j.wysocki@intel.com>,
        "Limonciello, Mario" <Mario.Limonciello@amd.com>,
        "viresh.kumar@linaro.org" <viresh.kumar@linaro.org>,
        "Sharma, Deepak" <Deepak.Sharma@amd.com>,
        "Fontenot, Nathan" <Nathan.Fontenot@amd.com>,
        "Deucher, Alexander" <Alexander.Deucher@amd.com>,
        "Huang, Shimmer" <Shimmer.Huang@amd.com>,
        "Du, Xiaojian" <Xiaojian.Du@amd.com>,
        "Meng, Li (Jassmine)" <Li.Meng@amd.com>,
        "Karny, Wyes" <Wyes.Karny@amd.com>,
        "linux-pm@vger.kernel.org" <linux-pm@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v10 04/12] cpufreq: amd-pstate: optimize driver working
 mode selection in amd_pstate_param()
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References: <20230106061420.95715-1-perry.yuan@amd.com>
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On Fri, Jan 06, 2023 at 02:14:12PM +0800, Yuan, Perry wrote:
> From: Wyes Karny <wyes.karny@amd.com>
> 
> The amd-pstate driver may support multiple working modes.
> Introduce a variable to keep track of which mode is currently enabled.
> Here we use cppc_state var to indicate which mode is enabled.
> This change will help to simplify the the amd_pstate_param() to choose
> which mode used for the following driver registration.
> 
> Reviewed-by: Mario Limonciello <mario.limonciello@amd.com>
> Signed-off-by: Perry Yuan <perry.yuan@amd.com>
> Signed-off-by: Wyes Karny <wyes.karny@amd.com>

Acked-by: Huang Rui <ray.huang@amd.com>

> ---
>  drivers/cpufreq/amd-pstate.c | 39 +++++++++++++++++++++++++++---------
>  include/linux/amd-pstate.h   | 17 ++++++++++++++++
>  2 files changed, 46 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
> index 204e39006dda..1a8b31277620 100644
> --- a/drivers/cpufreq/amd-pstate.c
> +++ b/drivers/cpufreq/amd-pstate.c
> @@ -60,7 +60,18 @@
>   * module parameter to be able to enable it manually for debugging.
>   */
>  static struct cpufreq_driver amd_pstate_driver;
> -static int cppc_load __initdata;
> +static int cppc_state = AMD_PSTATE_DISABLE;
> +
> +static inline int get_mode_idx_from_str(const char *str, size_t size)
> +{
> +	int i;
> +
> +	for (i=0; i < AMD_PSTATE_MAX; i++) {
> +		if (!strncmp(str, amd_pstate_mode_string[i], size))
> +			return i;
> +	}
> +	return -EINVAL;
> +}
>  
>  static inline int pstate_enable(bool enable)
>  {
> @@ -625,10 +636,10 @@ static int __init amd_pstate_init(void)
>  	/*
>  	 * by default the pstate driver is disabled to load
>  	 * enable the amd_pstate passive mode driver explicitly
> -	 * with amd_pstate=passive in kernel command line
> +	 * with amd_pstate=passive or other modes in kernel command line
>  	 */
> -	if (!cppc_load) {
> -		pr_debug("driver load is disabled, boot with amd_pstate=passive to enable this\n");
> +	if (cppc_state == AMD_PSTATE_DISABLE) {
> +		pr_debug("driver load is disabled, boot with specific mode to enable this\n");
>  		return -ENODEV;
>  	}
>  
> @@ -670,16 +681,24 @@ device_initcall(amd_pstate_init);
>  
>  static int __init amd_pstate_param(char *str)
>  {
> +	size_t size;
> +	int mode_idx;
> +
>  	if (!str)
>  		return -EINVAL;
>  
> -	if (!strcmp(str, "disable")) {
> -		cppc_load = 0;
> -		pr_info("driver is explicitly disabled\n");
> -	} else if (!strcmp(str, "passive"))
> -		cppc_load = 1;
> +	size = strlen(str);
> +	mode_idx = get_mode_idx_from_str(str, size);
>  
> -	return 0;
> +	if (mode_idx >= AMD_PSTATE_DISABLE && mode_idx < AMD_PSTATE_MAX) {
> +		cppc_state = mode_idx;
> +		if (cppc_state == AMD_PSTATE_DISABLE)
> +			pr_info("driver is explicitly disabled\n");
> +
> +		return 0;
> +	}
> +
> +	return -EINVAL;
>  }
>  early_param("amd_pstate", amd_pstate_param);
>  
> diff --git a/include/linux/amd-pstate.h b/include/linux/amd-pstate.h
> index 1c4b8659f171..dae2ce0f6735 100644
> --- a/include/linux/amd-pstate.h
> +++ b/include/linux/amd-pstate.h
> @@ -74,4 +74,21 @@ struct amd_cpudata {
>  	bool	boost_supported;
>  };
>  
> +/*
> + * enum amd_pstate_mode - driver working mode of amd pstate
> + */
> +enum amd_pstate_mode {
> +	AMD_PSTATE_DISABLE = 0,
> +	AMD_PSTATE_PASSIVE,
> +	AMD_PSTATE_ACTIVE,
> +	AMD_PSTATE_MAX,
> +};
> +
> +static const char * const amd_pstate_mode_string[] = {
> +	[AMD_PSTATE_DISABLE]     = "disable",
> +	[AMD_PSTATE_PASSIVE]     = "passive",
> +	[AMD_PSTATE_ACTIVE]      = "active",
> +	NULL,
> +};
> +
>  #endif /* _LINUX_AMD_PSTATE_H */
> -- 
> 2.34.1
>