Commit 08346675 authored by Gautham R. Shenoy's avatar Gautham R. Shenoy Committed by Rafael J. Wysocki
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cpufreq: ACPI: Fix max-frequency computation 



Commit 3c55e94c ("cpufreq: ACPI: Extend frequency tables to cover
boost frequencies") introduced an assumption in acpi_cpufreq_cpu_init()
that the first entry in the P-state table was the nominal frequency.
This assumption is incorrect. The frequency corresponding to the P0
P-State need not be the same as the nominal frequency advertised via
CPPC.

Since the driver is using the CPPC.highest_perf and CPPC.nominal_perf
to compute the boost-ratio, it makes sense to use CPPC.nominal_freq to
compute the max-frequency. CPPC.nominal_freq is advertised on
platforms supporting CPPC revisions 3 or higher.

Hence, fallback to using the first entry in the P-State table only on
platforms that do not advertise CPPC.nominal_freq.

Fixes: 3c55e94c ("cpufreq: ACPI: Extend frequency tables to cover boost frequencies")
Tested-by: default avatarDhananjay Ugwekar <Dhananjay.Ugwekar@amd.com>
Signed-off-by: default avatarGautham R. Shenoy <gautham.shenoy@amd.com>
Reviewed-by: default avatarMario Limonciello <mario.limonciello@amd.com>
Link: https://patch.msgid.link/20250113044107.566-1-gautham.shenoy@amd.com


[ rjw: Retain reverse X-mas tree ordering of local variable declarations ]
[ rjw: Subject and changelog edits ]
Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
parent 7420a7e8

drivers/cpufreq/acpi-cpufreq.c

+27 −9
Original line number Diff line number Diff line
@@ -623,7 +623,14 @@ static int acpi_cpufreq_blacklist(struct cpuinfo_x86 *c) 
#endif



#ifdef CONFIG_ACPI_CPPC_LIB

static u64 get_max_boost_ratio(unsigned int cpu)

/*

 * get_max_boost_ratio: Computes the max_boost_ratio as the ratio

 * between the highest_perf and the nominal_perf.

 *

 * Returns the max_boost_ratio for @cpu. Returns the CPPC nominal

 * frequency via @nominal_freq if it is non-NULL pointer.

 */

static u64 get_max_boost_ratio(unsigned int cpu, u64 *nominal_freq)

{

	struct cppc_perf_caps perf_caps;

	u64 highest_perf, nominal_perf;
@@ -652,6 +659,9 @@ static u64 get_max_boost_ratio(unsigned int cpu) 


	nominal_perf = perf_caps.nominal_perf;



	if (nominal_freq)

		*nominal_freq = perf_caps.nominal_freq;



	if (!highest_perf || !nominal_perf) {

		pr_debug("CPU%d: highest or nominal performance missing\n", cpu);

		return 0;
@@ -664,8 +674,12 @@ static u64 get_max_boost_ratio(unsigned int cpu) 


	return div_u64(highest_perf << SCHED_CAPACITY_SHIFT, nominal_perf);

}



#else

static inline u64 get_max_boost_ratio(unsigned int cpu) { return 0; }

static inline u64 get_max_boost_ratio(unsigned int cpu, u64 *nominal_freq)

{

	return 0;

}

#endif



static int acpi_cpufreq_cpu_init(struct cpufreq_policy *policy)
@@ -675,9 +689,9 @@ static int acpi_cpufreq_cpu_init(struct cpufreq_policy *policy) 
	struct acpi_cpufreq_data *data;

	unsigned int cpu = policy->cpu;

	struct cpuinfo_x86 *c = &cpu_data(cpu);

	u64 max_boost_ratio, nominal_freq = 0;

	unsigned int valid_states = 0;

	unsigned int result = 0;

	u64 max_boost_ratio;

	unsigned int i;

#ifdef CONFIG_SMP

	static int blacklisted;
@@ -827,16 +841,20 @@ static int acpi_cpufreq_cpu_init(struct cpufreq_policy *policy) 
	}

	freq_table[valid_states].frequency = CPUFREQ_TABLE_END;



	max_boost_ratio = get_max_boost_ratio(cpu);

	max_boost_ratio = get_max_boost_ratio(cpu, &nominal_freq);

	if (max_boost_ratio) {

		unsigned int freq = freq_table[0].frequency;

		unsigned int freq = nominal_freq;



		/*

		 * Because the loop above sorts the freq_table entries in the

		 * descending order, freq is the maximum frequency in the table.

		 * Assume that it corresponds to the CPPC nominal frequency and

		 * use it to set cpuinfo.max_freq.

		 * The loop above sorts the freq_table entries in the

		 * descending order. If ACPI CPPC has not advertised

		 * the nominal frequency (this is possible in CPPC

		 * revisions prior to 3), then use the first entry in

		 * the pstate table as a proxy for nominal frequency.

		 */

		if (!freq)

			freq = freq_table[0].frequency;



		policy->cpuinfo.max_freq = freq * max_boost_ratio >> SCHED_CAPACITY_SHIFT;

	} else {

		/*