intel_pstates: enable HWP when available

* don't reset the APERF and MPERF MSRs, they could be in use otherwise.
* use EPP or EPB to select power-save or performance mode
* HWP_REQUEST_PACKAGE disabled (as other OSes seem to do).

Change-Id: I26eb0b05c402b131a4ab174ad6f9ddf8e9367709
Reviewed-on: https://review.haiku-os.org/c/haiku/+/3222
Reviewed-by: Jérôme Duval <jerome.duval@gmail.com>

src/add-ons/kernel/power/cpufreq/intel_pstates/intel_pstates.cpp

@@ -1,4 +1,5 @@
 /*
+ * Copyright 2020, Jérôme Duval, jerome.duval@gmail.com.
  * Copyright 2013, Haiku, Inc. All Rights Reserved.
  * Distributed under the terms of the MIT License.
  *
@@ -24,6 +25,13 @@ const int kMinimalInterval = 50000;
 static uint16 sMinPState;
 static uint16 sMaxPState;
 static uint16 sBoostPState;
+static bool sHWPActive;
+static bool sHWPEPP;
+static uint8 sHWPLowest;
+static uint8 sHWPGuaranteed;
+static uint8 sHWPEfficient;
+static uint8 sHWPHighest;
+static bool sHWPPackage;
 
 static bool sAvoidBoost;
 
@@ -34,6 +42,9 @@ struct CPUEntry {
 	uint16		fCurrentPState;
 
 	bigtime_t	fLastUpdate;
+
+	uint64		fPrevAperf;
+	uint64		fPrevMperf;
 } CACHE_LINE_ALIGN;
 static CPUEntry* sCPUEntries;
 
@@ -46,10 +57,15 @@ CPUEntry::CPUEntry()
 }
 
 
+static void set_normal_pstate(void* /* dummy */, int cpu);
+
+
 static void
 pstates_set_scheduler_mode(scheduler_mode mode)
 {
 	sAvoidBoost = mode == SCHEDULER_MODE_POWER_SAVING;
+	if (sHWPActive)
+		call_all_cpus(set_normal_pstate, NULL);
 }
 
 
@@ -61,16 +77,16 @@ measure_pstate(CPUEntry* entry)
 	uint64 mperf = x86_read_msr(IA32_MSR_MPERF);
 	uint64 aperf = x86_read_msr(IA32_MSR_APERF);
 
-	x86_write_msr(IA32_MSR_MPERF, 0);
-	x86_write_msr(IA32_MSR_APERF, 0);
-
 	locker.Unlock();
 
-	if (mperf == 0)
+	if (mperf == 0 || mperf == entry->fPrevMperf)
 		return sMinPState;
 
-	int oldPState = sMaxPState * aperf / mperf;
+	int oldPState = sMaxPState * (aperf - entry->fPrevAperf)
+		/ (mperf - entry->fPrevMperf);
 	oldPState = min_c(max_c(oldPState, sMinPState), sBoostPState);
+	entry->fPrevAperf = aperf;
+	entry->fPrevMperf = mperf;
 
 	return oldPState;
 }
@@ -96,6 +112,9 @@ pstates_increase_performance(int delta)
 {
 	CPUEntry* entry = &sCPUEntries[smp_get_current_cpu()];
 
+	if (sHWPActive)
+		return B_NOT_SUPPORTED;
+
 	if (system_time() - entry->fLastUpdate < kMinimalInterval)
 		return B_OK;
 
@@ -115,6 +134,9 @@ pstates_decrease_performance(int delta)
 {
 	CPUEntry* entry = &sCPUEntries[smp_get_current_cpu()];
 
+	if (sHWPActive)
+		return B_NOT_SUPPORTED;
+
 	if (system_time() - entry->fLastUpdate < kMinimalInterval)
 		return B_OK;
 
@@ -161,8 +183,46 @@ is_cpu_model_supported(cpu_ent* cpu)
 static void
 set_normal_pstate(void* /* dummy */, int cpu)
 {
+	if (sHWPActive) {
+		if (x86_check_feature(IA32_FEATURE_HWP_NOTIFY, FEATURE_6_EAX))
+			x86_write_msr(IA32_MSR_HWP_INTERRUPT, 0);
+		x86_write_msr(IA32_MSR_PM_ENABLE, 1);
+		uint64 hwpRequest = x86_read_msr(IA32_MSR_HWP_REQUEST);
+		uint64 caps = x86_read_msr(IA32_MSR_HWP_CAPABILITIES);
+		sHWPLowest = IA32_HWP_CAPS_LOWEST_PERFORMANCE(caps);
+		sHWPEfficient = IA32_HWP_CAPS_EFFICIENT_PERFORMANCE(caps);
+		sHWPGuaranteed = IA32_HWP_CAPS_GUARANTEED_PERFORMANCE(caps);
+		sHWPHighest = IA32_HWP_CAPS_HIGHEST_PERFORMANCE(caps);
+
+		hwpRequest &= ~IA32_HWP_REQUEST_DESIRED_PERFORMANCE;
+		hwpRequest &= ~IA32_HWP_REQUEST_ACTIVITY_WINDOW;
+
+		hwpRequest &= ~IA32_HWP_REQUEST_MINIMUM_PERFORMANCE;
+		hwpRequest |= sHWPLowest;
+
+		hwpRequest &= ~IA32_HWP_REQUEST_MAXIMUM_PERFORMANCE;
+		hwpRequest |= sHWPHighest << 8;
+
+		if (x86_check_feature(IA32_FEATURE_HWP_EPP, FEATURE_6_EAX)) {
+			hwpRequest &= ~IA32_HWP_REQUEST_ENERGY_PERFORMANCE_PREFERENCE;
+			hwpRequest |= (sAvoidBoost ? 0x80ULL : 0x0ULL) << 24;
+		} else if (x86_check_feature(IA32_FEATURE_EPB, FEATURE_6_ECX)) {
+			uint64 perfBias = x86_read_msr(IA32_MSR_ENERGY_PERF_BIAS);
+			perfBias &= ~(0xfULL << 0);
+			perfBias |= (sAvoidBoost ? 0xfULL : 0x0ULL) << 0;
+			x86_write_msr(IA32_MSR_ENERGY_PERF_BIAS, perfBias);
+		}
+
+		if (sHWPPackage) {
+			x86_write_msr(IA32_MSR_HWP_REQUEST, hwpRequest
+				| IA32_HWP_REQUEST_PACKAGE_CONTROL);
+			x86_write_msr(IA32_MSR_HWP_REQUEST_PKG, hwpRequest);
+		} else
+			x86_write_msr(IA32_MSR_HWP_REQUEST, hwpRequest);
+	} else {
 		measure_pstate(&sCPUEntries[cpu]);
 		set_pstate(sMaxPState);
+	}
 }
 
 
@@ -181,13 +241,20 @@ init_pstates()
 			return B_ERROR;
 	}
 
-	sMinPState = (x86_read_msr(IA32_MSR_PLATFORM_INFO) >> 40) & 0xff;
+	uint64 platformInfo = x86_read_msr(IA32_MSR_PLATFORM_INFO);
-	sMaxPState = (x86_read_msr(IA32_MSR_PLATFORM_INFO) >> 8) & 0xff;
+	sHWPEPP = x86_check_feature(IA32_FEATURE_HWP_EPP, FEATURE_6_EAX);
+	sHWPActive = (x86_check_feature(IA32_FEATURE_HWP, FEATURE_6_EAX)
+		&& sHWPEPP);
+	sMinPState = (platformInfo >> 40) & 0xff;
+	sMaxPState = (platformInfo >> 8) & 0xff;
 	sBoostPState
 		= max_c(x86_read_msr(IA32_MSR_TURBO_RATIO_LIMIT) & 0xff, sMaxPState);
+	/* x86_check_feature(IA32_FEATURE_HWP_PLR, FEATURE_6_EAX)) */
+	sHWPPackage = false;
 
 	dprintf("using Intel P-States: min %" B_PRIu16 ", max %" B_PRIu16
-		", boost %" B_PRIu16 "\n", sMinPState, sMaxPState, sBoostPState);
+		", boost %" B_PRIu16 "%s\n", sMinPState, sMaxPState, sBoostPState,
+		sHWPActive ? ", HWP active" : "");
 
 	if (sMaxPState <= sMinPState || sMaxPState == 0) {
 		dprintf("unexpected or invalid Intel P-States limits, aborting\n");