[PATCH 4/6] ACPI: CPPC: Refactor boost ratio handling

Mario Limonciello (AMD)
2026-04-27T03:55:33Z

Rename amd_get_boost_ratio_numerator() to amd_get_effective_highest_perf()
to better reflect that it returns the effective highest performance value
for a CPU, accounting for preferred cores and heterogeneous topologies.

Add a new helper amd_get_boost_ratio() for doing both for boost
ratio calculations and update callers to use it.

This refactoring is needed because on some AMD systems (Zen6+),
the boost ratio should be calculated from frequency values rather than
performance values.

Signed-off-by: Mario Limonciello (AMD) <superm1@kernel.org>
---
arch/x86/kernel/acpi/cppc.c | 122 ++++++++++++++++++---------------
drivers/cpufreq/acpi-cpufreq.c | 5 +-
drivers/cpufreq/amd-pstate.c | 12 ++--
include/acpi/cppc_acpi.h | 9 ++-
4 files changed, 86 insertions(+), 62 deletions(-)

diff --git a/arch/x86/kernel/acpi/cppc.c b/arch/x86/kernel/acpi/cppc.c
index be4c5e9e5ff6f..b581447711079 100644
--- a/arch/x86/kernel/acpi/cppc.c
+++ b/arch/x86/kernel/acpi/cppc.c
@@ -81,31 +81,18 @@ int cpc_write_ffh(int cpunum, struct cpc_reg *reg, u64 val)

static void amd_set_max_freq_ratio(void)
{
- struct cppc_perf_caps perf_caps;
- u64 numerator, nominal_perf;
+ u64 numerator, denominator;
u64 perf_ratio;
int rc;

- rc = cppc_get_perf_caps(0, &perf_caps);
- if (rc) {
- pr_debug("Could not retrieve perf counters (%d)\n", rc);
- return;
- }
-
- rc = amd_get_boost_ratio_numerator(0, &numerator);
+ rc = amd_get_boost_ratio(0, &numerator, &denominator);
if (rc) {
- pr_debug("Could not retrieve highest performance (%d)\n", rc);
- return;
- }
- nominal_perf = perf_caps.nominal_perf;
-
- if (!nominal_perf) {
- pr_debug("Could not retrieve nominal performance\n");
+ pr_debug("Could not retrieve boost ratio (%d)\n", rc);
return;
}

/* midpoint between max_boost and max_P */
- perf_ratio = (div_u64(numerator * SCHED_CAPACITY_SCALE, nominal_perf) + SCHED_CAPACITY_SCALE) >> 1;
+ perf_ratio = (div_u64(numerator * SCHED_CAPACITY_SCALE, denominator) + SCHED_CAPACITY_SCALE) >> 1;

freq_invariance_set_perf_ratio(perf_ratio, false);
}
@@ -225,21 +212,18 @@ int amd_detect_prefcore(bool *detected)
EXPORT_SYMBOL_GPL(amd_detect_prefcore);

/**
- * 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.
+ * amd_get_effective_highest_perf: Get the effective highest performance value
+ * @cpu: CPU to get highest performance for.
*
- * 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.
+ * Get the effective highest performance value for a CPU, accounting for
+ * preferred cores and heterogeneous topologies. On systems with preferred
+ * cores, this may be a hardcoded value. On heterogeneous systems, this
+ * may be a per-CPU value. On other systems, this is the shared highest
+ * performance value.
*
- * If booting the system with amd-pstate enabled but preferred cores disabled then
- * the correct boost numerator will be returned to match hardware capabilities
- * even if the preferred cores scheduling hints are not enabled.
- *
- * Return: 0 for success, negative error code otherwise.
+ * Return: Effective highest performance value, or negative error code.
*/
-int amd_get_boost_ratio_numerator(unsigned int cpu, u64 *numerator)
+int amd_get_effective_highest_perf(unsigned int cpu)
{
enum x86_topology_cpu_type core_type = get_topology_cpu_type(&cpu_data(cpu));
bool prefcore;
@@ -247,14 +231,12 @@ int amd_get_boost_ratio_numerator(unsigned int cpu, u64 *numerator)
u32 tmp;

ret = amd_detect_prefcore(&prefcore);
- if (ret)
+ if (ret < 0)
return ret;

/* without preferred cores, return the highest perf register value */
- if (!prefcore) {
- *numerator = boost_numerator;
- return 0;
- }
+ if (!prefcore)
+ return boost_numerator;

/*
* For AMD CPUs with Family ID 19H and Model ID range 0x70 to 0x7f,
@@ -264,8 +246,7 @@ int amd_get_boost_ratio_numerator(unsigned int cpu, u64 *numerator)
if (cpu_feature_enabled(X86_FEATURE_ZEN4)) {
switch (boot_cpu_data.x86_model) {
case 0x70 ... 0x7f:
- *numerator = CPPC_HIGHEST_PERF_PERFORMANCE;
- return 0;
+ return CPPC_HIGHEST_PERF_PERFORMANCE;
default:
break;
}
@@ -273,26 +254,59 @@ int amd_get_boost_ratio_numerator(unsigned int cpu, u64 *numerator)

/* detect if running on heterogeneous design */
if (cpu_feature_enabled(X86_FEATURE_AMD_HTR_CORES)) {
- switch (core_type) {
- case TOPO_CPU_TYPE_UNKNOWN:
- pr_warn("Undefined core type found for cpu %d\n", cpu);
- break;
- case TOPO_CPU_TYPE_PERFORMANCE:
- /* use the max scale for performance cores */
- *numerator = CPPC_HIGHEST_PERF_PERFORMANCE;
- return 0;
- case TOPO_CPU_TYPE_EFFICIENCY:
- /* use the highest perf value for efficiency cores */
- ret = amd_get_highest_perf(cpu, &tmp);
- if (ret)
- return ret;
- *numerator = tmp;
- return 0;
- }
+ if (cpu_feature_enabled(X86_FEATURE_ZEN5) &&
+ core_type == TOPO_CPU_TYPE_PERFORMANCE)
+ return CPPC_HIGHEST_PERF_PERFORMANCE;
+
+ /* Zen 5 efficiency, and Zen 6+ */
+ ret = amd_get_highest_perf(cpu, &tmp);
+ if (ret < 0)
+ return ret;
+
+ return tmp;
+ }
+
+ return CPPC_HIGHEST_PERF_PREFCORE;
+}
+EXPORT_SYMBOL_GPL(amd_get_effective_highest_perf);
+
+/**
+ * amd_get_boost_ratio: Get numerator and denominator for boost ratio
+ * @cpu: CPU to get the boost ratio for.
+ * @numerator: Output variable for numerator.
+ * @denominator: Output variable for denominator.
+ *
+ * Get the numerator and denominator for calculating the boost ratio.
+ *
+ * Return: 0 for success, negative error code otherwise.
+ */
+int amd_get_boost_ratio(unsigned int cpu, u64 *numerator, u64 *denominator)
+{
+ struct cppc_perf_caps perf_caps;
+ int ret;
+
+ ret = cppc_get_perf_caps(cpu, &perf_caps);
+ if (ret)
+ return ret;
+
+ /* Use frequency values if available */
+ if (perf_caps.highest_freq && perf_caps.nominal_freq) {
+ *numerator = perf_caps.highest_freq;
+ *denominator = perf_caps.nominal_freq;
+ return 0;
}

- *numerator = CPPC_HIGHEST_PERF_PREFCORE;
+ /* Fall back to performance values */
+ ret = amd_get_effective_highest_perf(cpu);
+ if (ret < 0)
+ return ret;
+
+ *numerator = ret;
+
+ *denominator = perf_caps.nominal_perf;
+ if (!*denominator)
+ return -EINVAL;

return 0;
}
-EXPORT_SYMBOL_GPL(amd_get_boost_ratio_numerator);
+EXPORT_SYMBOL_GPL(amd_get_boost_ratio);
diff --git a/drivers/cpufreq/acpi-cpufreq.c b/drivers/cpufreq/acpi-cpufreq.c
index 21639d9ac753b..a1a005b29daba 100644
--- a/drivers/cpufreq/acpi-cpufreq.c
+++ b/drivers/cpufreq/acpi-cpufreq.c
@@ -640,12 +640,13 @@ static u64 get_max_boost_ratio(unsigned int cpu, u64 *nominal_freq)
}

if (boot_cpu_data.x86_vendor == X86_VENDOR_AMD) {
- ret = amd_get_boost_ratio_numerator(cpu, &highest_perf);
- if (ret) {
+ ret = amd_get_effective_highest_perf(cpu);
+ if (ret < 0) {
pr_debug("CPU%d: Unable to get boost ratio numerator (%d)\n",
cpu, ret);
return 0;
}
+ highest_perf = ret;
} else {
highest_perf = perf_caps.highest_perf;
}
diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
index 453084c67327f..f5c7cc05220c4 100644
--- a/drivers/cpufreq/amd-pstate.c
+++ b/drivers/cpufreq/amd-pstate.c
@@ -476,10 +476,12 @@ static int msr_init_perf(struct amd_cpudata *cpudata)
if (ret)
return ret;

- ret = amd_get_boost_ratio_numerator(cpudata->cpu, &numerator);
- if (ret)
+ ret = amd_get_effective_highest_perf(cpudata->cpu);
+ if (ret < 0)
return ret;

+ numerator = ret;
+
ret = rdmsrl_on_cpu(cpudata->cpu, MSR_AMD_CPPC_REQ, &cppc_req);
if (ret)
return ret;
@@ -520,10 +522,12 @@ static int shmem_init_perf(struct amd_cpudata *cpudata)
if (ret)
return ret;

- ret = amd_get_boost_ratio_numerator(cpudata->cpu, &numerator);
- if (ret)
+ ret = amd_get_effective_highest_perf(cpudata->cpu);
+ if (ret < 0)
return ret;

+ numerator = ret;
+
perf.highest_perf = numerator;
perf.max_limit_perf = numerator;
perf.min_limit_perf = cppc_perf.lowest_perf;
diff --git a/include/acpi/cppc_acpi.h b/include/acpi/cppc_acpi.h
index 79f1eef957a45..c25755630f8be 100644
--- a/include/acpi/cppc_acpi.h
+++ b/include/acpi/cppc_acpi.h
@@ -193,7 +193,8 @@ extern int cppc_set_auto_sel(int cpu, bool enable);
extern int cppc_get_perf_limited(int cpu, u64 *perf_limited);
extern int cppc_set_perf_limited(int cpu, u64 bits_to_clear);
extern int amd_get_highest_perf(unsigned int cpu, u32 *highest_perf);
-extern int amd_get_boost_ratio_numerator(unsigned int cpu, u64 *numerator);
+extern int amd_get_effective_highest_perf(unsigned int cpu);
+extern int amd_get_boost_ratio(unsigned int cpu, u64 *numerator, u64 *denominator);
extern int amd_detect_prefcore(bool *detected);
#else /* !CONFIG_ACPI_CPPC_LIB */
static inline int cppc_get_desired_perf(int cpunum, u64 *desired_perf)
@@ -300,7 +301,11 @@ static inline int amd_get_highest_perf(unsigned int cpu, u32 *highest_perf)
{
return -ENODEV;
}
-static inline int amd_get_boost_ratio_numerator(unsigned int cpu, u64 *numerator)
+static inline int amd_get_effective_highest_perf(unsigned int cpu)
+{
+ return -EOPNOTSUPP;
+}
+static inline int amd_get_boost_ratio(unsigned int cpu, u64 *numerator, u64 *denominator)
{
return -EOPNOTSUPP;
}
--
2.43.0