linux-kernel - Re: [PATCH v2 10/10] cpufreq: amd-pstate: automatically load pstate driver by default

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Date: Mon, 13 May 2024 15:06:58 +0530
From: Dhananjay Ugwekar <Dhananjay.Ugwekar@....com>
To: Perry Yuan <perry.yuan@....com>, Mario.Limonciello@....com,
 gautham.shenoy@....com, Ray.Huang@....com, Borislav.Petkov@....com
Cc: rafael.j.wysocki@...el.com, 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 v2 10/10] cpufreq: amd-pstate: automatically load pstate
 driver by default

Hello Perry,

On 5/13/2024 7:37 AM, 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.
> 
> [    0.917789] usb usb6: Manufacturer: Linux 6.9.0-rc6-amd-pstate-new-fix-v1 xhci-hcd
> [    0.982579] amd_pstate: failed to register with return -22
> 
> 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>
> ---
>  drivers/cpufreq/amd-pstate.c | 36 +++++++++++++++++++-----------------
>  1 file changed, 19 insertions(+), 17 deletions(-)
> 
> diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
> index dce901a403c9..03342fef7d94 100644
> --- a/drivers/cpufreq/amd-pstate.c
> +++ b/drivers/cpufreq/amd-pstate.c
> @@ -1785,28 +1785,30 @@ static int __init amd_pstate_init(void)
>  	/* check if this machine need CPPC quirks */
>  	dmi_check_system(amd_pstate_quirks_table);
>  
> +	/* get default driver mode for loading */
> +	if (cppc_state == AMD_PSTATE_UNDEFINED)
> +		cppc_state = CONFIG_X86_AMD_PSTATE_DEFAULT_MODE;
> +
> +	/* Disable on the following configs by default:
> +	 * 1. Undefined platforms
> +	 * 2. Server platforms
> +	 */
> +	if (amd_pstate_acpi_pm_profile_undefined() ||
> +		amd_pstate_acpi_pm_profile_server()) {
> +		pr_info("driver load is disabled for server or undefined platform\n");
> +		return -ENODEV;
> +	}
> +

Wont this change make it impossible to use amd-pstate on server platforms? It wont work
even if we pass "amd-pstate=active" in cmdline, because this check is before the switch
case.

Thanks,
Dhananjay

>  	switch (cppc_state) {
> -	case AMD_PSTATE_UNDEFINED:
> -		/* Disable on the following configs by default:
> -		 * 1. Undefined platforms
> -		 * 2. Server platforms
> -		 * 3. Shared memory designs
> -		 */
> -		if (amd_pstate_acpi_pm_profile_undefined() ||
> -		    amd_pstate_acpi_pm_profile_server() ||
> -		    !cpu_feature_enabled(X86_FEATURE_CPPC)) {
> -			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;
>  	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;
> @@ -1827,7 +1829,7 @@ 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;
>  	}
>