linux-kernel - Re: [PATCH 2/8] x86/amd: Rename amd_get_highest_perf() to amd_get_boost_ratio

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Message-ID: <3a8a2d6e-c9a7-42b4-9619-d1f86f9f3135@amd.com>
Date: Tue, 27 Aug 2024 13:18:46 -0500
From: Mario Limonciello <mario.limonciello@....com>
To: "Gautham R. Shenoy" <gautham.shenoy@....com>,
 Mario Limonciello <superm1@...nel.org>
Cc: Borislav Petkov <bp@...en8.de>, Perry Yuan <perry.yuan@....com>,
 "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" <x86@...nel.org>,
 "Rafael J . Wysocki" <rafael@...nel.org>,
 "open list:X86 ARCHITECTURE (32-BIT AND 64-BIT)"
 <linux-kernel@...r.kernel.org>, "open list:ACPI"
 <linux-acpi@...r.kernel.org>,
 "open list:CPU FREQUENCY SCALING FRAMEWORK" <linux-pm@...r.kernel.org>
Subject: Re: [PATCH 2/8] x86/amd: Rename amd_get_highest_perf() to
 amd_get_boost_ratio_numerator()

On 8/27/2024 09:42, Gautham R. Shenoy wrote:
> Hello Mario,
> 
> On Mon, Aug 26, 2024 at 04:13:52PM -0500, Mario Limonciello wrote:
>> From: Mario Limonciello <mario.limonciello@....com>
>>
>> The function name is ambiguous because it returns an intermediate value
>> for calculating maximum frequency rather than the CPPC 'Highest Perf'
>> register.
>>
>> Rename the function to clarify its use and allow the function to return
>> errors. Adjust the consumer in acpi-cpufreq to catch errors.
>>
>> Signed-off-by: Mario Limonciello <mario.limonciello@....com>
> [..snip..]
> 
>> --- a/arch/x86/kernel/acpi/cppc.c
>> +++ b/arch/x86/kernel/acpi/cppc.c
>> @@ -79,11 +79,13 @@ static void amd_set_max_freq_ratio(void)
>>   		return;
>>   	}
>>   
>> -	highest_perf = amd_get_highest_perf();
>> +	rc = amd_get_boost_ratio_numerator(0, &highest_perf);
> 
> The variable is still named highest_perf, here! I suppose that will
> change in a subsequent patch?
> 
> 
> 
>> +	if (rc)
>> +		pr_debug("Could not retrieve highest performance\n");
> 
> I understand that amd_get_boost_ratio_numerator() always returns a 0
> in this patch and thus rc == 0, which means we never enter this "if"
> condition.
> 
> However, when rc is non-zero, shouldn't this function return after
> printing the debug message?

Both good points.  Will fix for v2.

> 
> --
> Thanks and Regards
> gautham.
> 
> 
> 
> 
>>   	nominal_perf = perf_caps.nominal_perf;
>>   
>> -	if (!highest_perf || !nominal_perf) {
>> -		pr_debug("Could not retrieve highest or nominal performance\n");
>> +	if (!nominal_perf) {
>> +		pr_debug("Could not retrieve nominal performance\n");
>>   		return;
>>   	}
>>   
>> @@ -117,18 +119,34 @@ void init_freq_invariance_cppc(void)
>>   	mutex_unlock(&freq_invariance_lock);
>>   }
>>   
>> -u32 amd_get_highest_perf(void)
>> +/**
>> + * amd_get_boost_ratio_numerator: Get the numerator to use for boost ratio calculation
>> + * @cpu: CPU to get numerator for.
>> + * @numerator: Output variable for numerator.
>> + *
>> + * Determine the numerator to use for calculating the boost ratio on
>> + * a CPU. On systems that support preferred cores, this will be a hardcoded
>> + * value. On other systems this will the highest performance register value.
>> + *
>> + * Return: 0 for success, negative error code otherwise.
>> + */
>> +int amd_get_boost_ratio_numerator(unsigned int cpu, u64 *numerator)
>>   {
>>   	struct cpuinfo_x86 *c = &boot_cpu_data;
>>   
>>   	if (c->x86 == 0x17 && ((c->x86_model >= 0x30 && c->x86_model < 0x40) ||
>> -			       (c->x86_model >= 0x70 && c->x86_model < 0x80)))
>> -		return 166;
>> +			       (c->x86_model >= 0x70 && c->x86_model < 0x80))) {
>> +		*numerator = 166;
>> +		return 0;
>> +	}
>>   
>>   	if (c->x86 == 0x19 && ((c->x86_model >= 0x20 && c->x86_model < 0x30) ||
>> -			       (c->x86_model >= 0x40 && c->x86_model < 0x70)))
>> -		return 166;
>> +			       (c->x86_model >= 0x40 && c->x86_model < 0x70))) {
>> +		*numerator = 166;
>> +		return 0;
>> +	}
>> +	*numerator = 255;
>>   
>> -	return 255;
>> +	return 0;
>>   }
>> -EXPORT_SYMBOL_GPL(amd_get_highest_perf);
>> +EXPORT_SYMBOL_GPL(amd_get_boost_ratio_numerator);
>> diff --git a/drivers/cpufreq/acpi-cpufreq.c b/drivers/cpufreq/acpi-cpufreq.c
>> index a8ca625a98b89..0f04feb6cafaf 100644
>> --- a/drivers/cpufreq/acpi-cpufreq.c
>> +++ b/drivers/cpufreq/acpi-cpufreq.c
>> @@ -642,10 +642,16 @@ static u64 get_max_boost_ratio(unsigned int cpu)
>>   		return 0;
>>   	}
>>   
>> -	if (boot_cpu_data.x86_vendor == X86_VENDOR_AMD)
>> -		highest_perf = amd_get_highest_perf();
>> -	else
>> +	if (boot_cpu_data.x86_vendor == X86_VENDOR_AMD) {
>> +		ret = amd_get_boost_ratio_numerator(cpu, &highest_perf);
>> +		if (ret) {
>> +			pr_debug("CPU%d: Unable to get boost ratio numerator (%d)\n",
>> +				 cpu, ret);
>> +			return 0;
>> +		}
>> +	} else {
>>   		highest_perf = perf_caps.highest_perf;
>> +	}
>>   
>>   	nominal_perf = perf_caps.nominal_perf;
>>   
>> diff --git a/include/acpi/cppc_acpi.h b/include/acpi/cppc_acpi.h
>> index 930b6afba6f4d..f25a881cd46dd 100644
>> --- a/include/acpi/cppc_acpi.h
>> +++ b/include/acpi/cppc_acpi.h
>> @@ -136,6 +136,12 @@ struct cppc_cpudata {
>>   	cpumask_var_t shared_cpu_map;
>>   };
>>   
>> +#ifdef CONFIG_CPU_SUP_AMD
>> +extern int amd_get_boost_ratio_numerator(unsigned int cpu, u64 *numerator);
>> +#else /* !CONFIG_CPU_SUP_AMD */
>> +static inline int amd_get_boost_ratio_numerator(unsigned int cpu, u64 *numerator) { return -ENODEV; }
>> +#endif /* !CONFIG_CPU_SUP_AMD */
>> +
>>   #ifdef CONFIG_ACPI_CPPC_LIB
>>   extern int cppc_get_desired_perf(int cpunum, u64 *desired_perf);
>>   extern int cppc_get_nominal_perf(int cpunum, u64 *nominal_perf);
>> -- 
>> 2.43.0
>>