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

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Message-ID: <2728771.mvXUDI8C0e@natalenko.name>
Date: Wed, 08 May 2024 17:20:39 +0200
From: Oleksandr Natalenko <oleksandr@...alenko.name>
To: Perry Yuan <perry.yuan@....com>, rafael.j.wysocki@...el.com,
 viresh.kumar@...aro.org, Ray.Huang@....com, gautham.shenoy@....com,
 Borislav.Petkov@....com, Mario Limonciello <mario.limonciello@....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 11/11] cpufreq: amd-pstate: automatically load pstate driver by
 default

Hello.

On úterý 7. května 2024 16:41:29, SELČ Mario Limonciello wrote:
> On 5/7/2024 02:15, 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 | 39 +++++++++++++++++++-----------------
> >   1 file changed, 21 insertions(+), 18 deletions(-)
> > 
> > diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
> > index 3ff381c4edf7..f5368497ee79 100644
> > --- a/drivers/cpufreq/amd-pstate.c
> > +++ b/drivers/cpufreq/amd-pstate.c
> > @@ -66,7 +66,7 @@
> >   static struct cpufreq_driver *current_pstate_driver;
> >   static struct cpufreq_driver amd_pstate_driver;
> >   static struct cpufreq_driver amd_pstate_epp_driver;
> > -static int cppc_state = AMD_PSTATE_UNDEFINED;
> > +static int cppc_state;
> >   static bool cppc_enabled;
> >   static bool amd_pstate_prefcore = true;
> >   static struct quirk_entry *quirks;
> > @@ -1762,6 +1762,16 @@ static int __init amd_pstate_init(void)
> >   	if (boot_cpu_data.x86_vendor != X86_VENDOR_AMD)
> >   		return -ENODEV;
> >   
> > +	/* 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;
> > +	}
> > +
> >   	/* show debug message only if CPPC is not supported */
> >   	if (!amd_cppc_supported())
> >   		return -EOPNOTSUPP;
> > @@ -1781,28 +1791,21 @@ 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*/
> > +	cppc_state = CONFIG_X86_AMD_PSTATE_DEFAULT_MODE;
> 
> Rather than setting it here within amd_pstate_init() I think you can 
> just set it at line 67 to CONFIG_X86_AMD_PSTATE_DEFAULT_MODE.

To me it seems like setting it here kills a possibility to set the mode via the kernel cmdline. Regardless of what will be set in `amd_pstate=`, `CONFIG_X86_AMD_PSTATE_DEFAULT_MODE` will be used instead.

> 
> > +	pr_debug("cppc working state set to mode:%d\n", cppc_state);
> 
> I think this debug line is going to be unnecessary when it's already 
> hardcoded to kernel config.
> 
> > +
> >   	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_UNDEFINED:
> 
> With the intent of this patch I no longer see a need for 
> AMD_PSTATE_UNDEFINED in the rest of the driver (or in this case 
> statement even).
> 
> I feel you can drop it from amd-pstate.h.
> 
> >   	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;
> > @@ -1823,7 +1826,7 @@ 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) with return %d\n", cppc_state, ret);
> >   		return ret;
> >   	}
> >   
> 
> 
> 


-- 
Oleksandr Natalenko (post-factum)
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