AMD heterogeneous designs include two types of cores:
 * Performance
 * Efficiency

Each core type has different highest performance values configured by the
platform.  Drivers such as `amd_pstate` need to identify the type of
core to correctly set an appropriate boost numerator to calculate the
maximum frequency.

X86_FEATURE_AMD_HETEROGENEOUS_CORES is used to identify whether the SoC
supports heterogeneous core type by reading CPUID leaf Fn_0x80000026.

On performance cores the scaling factor of 196 is used.  On efficiency
cores the scaling factor is the value reported as the highest perf.
Efficiency cores have the same preferred core rankings.

Tested-by: Eric Naim <dnaim@cachyos.org>
Tested-by: Peter Jung <ptr1337@cachyos.org>
Suggested-by: Perry Yuan <perry.yuan@amd.com>
Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
---
v3->v4:
 * Drop default case and show warning in unknown case if hetero cores
   were detected (Boris)
 * Change get_topology_generic_cpu_type to get_topology_cpu_type (Mario)
 * Only performance boost numerator to hetero designs.  This fixes
   an issue on Zen5 9950X which supports the CPUID for identifying core
   types but only has performance cores (Peter Jung)
---
 arch/x86/kernel/acpi/cppc.c | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)

diff --git a/arch/x86/kernel/acpi/cppc.c b/arch/x86/kernel/acpi/cppc.c
index 956984054bf30..59edf64ad9edc 100644
--- a/arch/x86/kernel/acpi/cppc.c
+++ b/arch/x86/kernel/acpi/cppc.c
@@ -234,8 +234,10 @@ EXPORT_SYMBOL_GPL(amd_detect_prefcore);
  */
 int amd_get_boost_ratio_numerator(unsigned int cpu, u64 *numerator)
 {
+	enum x86_topology_cpu_type core_type = get_topology_cpu_type(&cpu_data(cpu));
 	bool prefcore;
 	int ret;
+	u32 tmp;
 
 	ret = amd_detect_prefcore(&prefcore);
 	if (ret)
@@ -261,6 +263,27 @@ int amd_get_boost_ratio_numerator(unsigned int cpu, u64 *numerator)
 			break;
 		}
 	}
+
+	/* detect if running on heterogeneous design */
+	if (cpu_feature_enabled(X86_FEATURE_AMD_HETEROGENEOUS_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;
+		}
+	}
+
 	*numerator = CPPC_HIGHEST_PERF_PREFCORE;
 
 	return 0;
-- 
2.43.0

The following commit has been merged into the x86/cpu branch of tip:

Commit-ID:     3eef25ab0d89cb1e55699a4d242c5afe17dbbd07
Gitweb:        https://git.kernel.org/tip/3eef25ab0d89cb1e55699a4d242c5afe17dbbd07
Author:        Mario Limonciello <mario.limonciello@amd.com>
AuthorDate:    Fri, 25 Oct 2024 12:14:59 -05:00
Committer:     Borislav Petkov (AMD) <bp@alien8.de>
CommitterDate: Fri, 25 Oct 2024 20:51:17 +02:00

x86/amd: Use heterogeneous core topology for identifying boost numerator

AMD heterogeneous designs include two types of cores:

 * Performance
 * Efficiency

Each core type has different highest performance values configured by the
platform.  Drivers such as amd_pstate need to identify the type of core to
correctly set an appropriate boost numerator to calculate the maximum
frequency.

X86_FEATURE_AMD_HETEROGENEOUS_CORES is used to identify whether the SoC
supports heterogeneous core type by reading CPUID leaf Fn_0x80000026.

On performance cores the scaling factor of 196 is used.  On efficiency cores
the scaling factor is the value reported as the highest perf.  Efficiency
cores have the same preferred core rankings.

Suggested-by: Perry Yuan <perry.yuan@amd.com>
Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20241025171459.1093-6-mario.limonciello@amd.com
---
 arch/x86/kernel/acpi/cppc.c | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)

diff --git a/arch/x86/kernel/acpi/cppc.c b/arch/x86/kernel/acpi/cppc.c
index 9569840..59edf64 100644
--- a/arch/x86/kernel/acpi/cppc.c
+++ b/arch/x86/kernel/acpi/cppc.c
@@ -234,8 +234,10 @@ EXPORT_SYMBOL_GPL(amd_detect_prefcore);
  */
 int amd_get_boost_ratio_numerator(unsigned int cpu, u64 *numerator)
 {
+	enum x86_topology_cpu_type core_type = get_topology_cpu_type(&cpu_data(cpu));
 	bool prefcore;
 	int ret;
+	u32 tmp;
 
 	ret = amd_detect_prefcore(&prefcore);
 	if (ret)
@@ -261,6 +263,27 @@ int amd_get_boost_ratio_numerator(unsigned int cpu, u64 *numerator)
 			break;
 		}
 	}
+
+	/* detect if running on heterogeneous design */
+	if (cpu_feature_enabled(X86_FEATURE_AMD_HETEROGENEOUS_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;
+		}
+	}
+
 	*numerator = CPPC_HIGHEST_PERF_PREFCORE;
 
 	return 0;