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cpufreq: ACPI: Fix max-frequency computation

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Commit 3c55e94c0a ("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: 3c55e94c0a ("cpufreq: ACPI: Extend frequency tables to cover boost frequencies")
Tested-by: Dhananjay Ugwekar <Dhananjay.Ugwekar@amd.com>
Signed-off-by: Gautham R. Shenoy <gautham.shenoy@amd.com>
Reviewed-by: Mario 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: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
This commit is contained in:
Gautham R. Shenoy 2025-01-13 10:11:07 +05:30 committed by Rafael J. Wysocki
parent 7420a7e867
commit 0834667545
1 changed files with 27 additions and 9 deletions
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36
drivers/cpufreq/acpi-cpufreq.c
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@ -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 {
/*