This is a note to let you know that I've just added the patch titled
cpufreq: ACPI: Fix max-frequency computation
to the 5.15-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
cpufreq-acpi-fix-max-frequency-computation.patch
and it can be found in the queue-5.15 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit ee4a8775a1310a3ac3f0514d94d5c198810c0c30
Author: Gautham R. Shenoy <gautham.shenoy@xxxxxxx>
Date: Mon Jan 13 10:11:07 2025 +0530
cpufreq: ACPI: Fix max-frequency computation
[ Upstream commit 0834667545962ef1c5e8684ed32b45d9c574acd3 ]
Commit 3c55e94c0ade ("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: 3c55e94c0ade ("cpufreq: ACPI: Extend frequency tables to cover boost frequencies")
Tested-by: Dhananjay Ugwekar <Dhananjay.Ugwekar@xxxxxxx>
Signed-off-by: Gautham R. Shenoy <gautham.shenoy@xxxxxxx>
Reviewed-by: Mario Limonciello <mario.limonciello@xxxxxxx>
Link: https://patch.msgid.link/20250113044107.566-1-gautham.shenoy@xxxxxxx
[ 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@xxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/drivers/cpufreq/acpi-cpufreq.c b/drivers/cpufreq/acpi-cpufreq.c
index 28467d83c7452..4a31bd90406c9 100644
--- a/drivers/cpufreq/acpi-cpufreq.c
+++ b/drivers/cpufreq/acpi-cpufreq.c
@@ -630,7 +630,14 @@ 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;
@@ -653,6 +660,9 @@ 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;
@@ -665,8 +675,12 @@ 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)
@@ -676,9 +690,9 @@ 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;
@@ -828,16 +842,20 @@ 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 {
/*
