[PATCH v1 1/2] cpufreq: intel_pstate: Use CPPC to get scaling factors

[Rafael J. Wysocki]

From: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>

The perf-to-frequency scaling factors are used by intel_pstate on hybrid
platforms to cast performance levels to frequency on different types of
CPUs which is needed because the generic cpufreq sysfs interface works
in the frequency domain.

For some hybrid platforms already in the field, the scaling factors are
known, but for others (including some upcoming ones) they most likely
will be different and the only way to get them that scales is to use
information provided by the platform firmware.  In this particular case,
the requisite information can be obtained via CPPC.

If the P-core hybrid scaling factor for the given processor model is not
known, use CPPC to compute hybrid scaling factors for all CPUs.

Since the current default hybrid scaling factor is only suitable for a
few early hybrid platforms, add intel_hybrid_scaling_factor[] entries
for them and initialize the scaling factor to zero ("unknown") by
default.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
---
 drivers/cpufreq/intel_pstate.c |   59 +++++++++++++++++++++++------------------
 1 file changed, 34 insertions(+), 25 deletions(-)

Index: linux-pm/drivers/cpufreq/intel_pstate.c
===================================================================
--- linux-pm.orig/drivers/cpufreq/intel_pstate.c
+++ linux-pm/drivers/cpufreq/intel_pstate.c
@@ -28,6 +28,7 @@
 #include <linux/pm_qos.h>
 #include <linux/bitfield.h>
 #include <trace/events/power.h>
+#include <linux/units.h>
 
 #include <asm/cpu.h>
 #include <asm/div64.h>
@@ -302,11 +303,11 @@ static bool hwp_is_hybrid;
 
 static struct cpufreq_driver *intel_pstate_driver __read_mostly;
 
-#define HYBRID_SCALING_FACTOR		78741
+#define HYBRID_SCALING_FACTOR_ADL	78741
 #define HYBRID_SCALING_FACTOR_MTL	80000
 #define HYBRID_SCALING_FACTOR_LNL	86957
 
-static int hybrid_scaling_factor = HYBRID_SCALING_FACTOR;
+static int hybrid_scaling_factor;
 
 static inline int core_get_scaling(void)
 {
@@ -414,18 +415,15 @@ static int intel_pstate_get_cppc_guarant
 static int intel_pstate_cppc_get_scaling(int cpu)
 {
 	struct cppc_perf_caps cppc_perf;
-	int ret;
-
-	ret = cppc_get_perf_caps(cpu, &cppc_perf);
 
 	/*
-	 * If the nominal frequency and the nominal performance are not
-	 * zero and the ratio between them is not 100, return the hybrid
-	 * scaling factor.
-	 */
-	if (!ret && cppc_perf.nominal_perf && cppc_perf.nominal_freq &&
-	    cppc_perf.nominal_perf * 100 != cppc_perf.nominal_freq)
-		return hybrid_scaling_factor;
+	 * Compute the perf-to-frequency scaling factor for the given CPU if
+	 * possible, unless it would be 0.
+	 */
+	if (!cppc_get_perf_caps(cpu, &cppc_perf) &&
+	    cppc_perf.nominal_perf && cppc_perf.nominal_freq)
+		return div_u64(cppc_perf.nominal_freq * KHZ_PER_MHZ,
+			       cppc_perf.nominal_perf);
 
 	return core_get_scaling();
 }
@@ -2211,24 +2209,30 @@ static void hybrid_get_type(void *data)
 
 static int hwp_get_cpu_scaling(int cpu)
 {
-	u8 cpu_type = 0;
+	if (hybrid_scaling_factor) {
+		u8 cpu_type = 0;
+
+		smp_call_function_single(cpu, hybrid_get_type, &cpu_type, 1);
 
-	smp_call_function_single(cpu, hybrid_get_type, &cpu_type, 1);
-	/* P-cores have a smaller perf level-to-freqency scaling factor. */
-	if (cpu_type == 0x40)
-		return hybrid_scaling_factor;
+		/*
+		 * Return the hybrid scaling factor for P-cores and use the
+		 * default core scaling for E-cores.
+		 */
+		if (cpu_type == 0x40)
+			return hybrid_scaling_factor;
 
-	/* Use default core scaling for E-cores */
-	if (cpu_type == 0x20)
+		if (cpu_type == 0x20)
+			return core_get_scaling();
+	}
+
+	/* Use core scaling on non-hybrid systems. */
+	if (!cpu_feature_enabled(X86_FEATURE_HYBRID_CPU))
 		return core_get_scaling();
 
 	/*
-	 * If reached here, this system is either non-hybrid (like Tiger
-	 * Lake) or hybrid-capable (like Alder Lake or Raptor Lake) with
-	 * no E cores (in which case CPUID for hybrid support is 0).
-	 *
-	 * The CPPC nominal_frequency field is 0 for non-hybrid systems,
-	 * so the default core scaling will be used for them.
+	 * The system is hybrid, but the hybrid scaling factor is not known or
+	 * the CPU type is not one of the above, so use CPPC to compute the
+	 * scaling factor for this CPU.
 	 */
 	return intel_pstate_cppc_get_scaling(cpu);
 }
@@ -3665,6 +3669,11 @@ static const struct x86_cpu_id intel_epp
 };
 
 static const struct x86_cpu_id intel_hybrid_scaling_factor[] = {
+	X86_MATCH_VFM(INTEL_ALDERLAKE, HYBRID_SCALING_FACTOR_ADL),
+	X86_MATCH_VFM(INTEL_ALDERLAKE_L, HYBRID_SCALING_FACTOR_ADL),
+	X86_MATCH_VFM(INTEL_RAPTORLAKE, HYBRID_SCALING_FACTOR_ADL),
+	X86_MATCH_VFM(INTEL_RAPTORLAKE_P, HYBRID_SCALING_FACTOR_ADL),
+	X86_MATCH_VFM(INTEL_RAPTORLAKE_S, HYBRID_SCALING_FACTOR_ADL),
 	X86_MATCH_VFM(INTEL_METEORLAKE_L, HYBRID_SCALING_FACTOR_MTL),
 	X86_MATCH_VFM(INTEL_ARROWLAKE, HYBRID_SCALING_FACTOR_MTL),
 	X86_MATCH_VFM(INTEL_LUNARLAKE_M, HYBRID_SCALING_FACTOR_LNL),