cpufreq: AMD "frequency sensitivity feedback" powersave bias for ondemand governor
Future AMD processors, starting with Family 16h, can provide software
with feedback on how the workload may respond to frequency change --
memory-bound workloads will not benefit from higher frequency, where
as compute-bound workloads will. This patch enables this "frequency
sensitivity feedback" to aid the ondemand governor to make better
frequency change decisions by hooking into the powersave bias.
Signed-off-by: Jacob Shin <jacob.shin@amd.com>
Acked-by: Thomas Renninger <trenn@suse.de>
Acked-by: Borislav Petkov <bp@suse.de>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
diff --git a/Documentation/cpu-freq/governors.txt b/Documentation/cpu-freq/governors.txt
index 4dfed30..66f9cc3 100644
--- a/Documentation/cpu-freq/governors.txt
+++ b/Documentation/cpu-freq/governors.txt
@@ -167,6 +167,27 @@
busy, rather than shifting back and forth in speed. This tunable has no
effect on behavior at lower speeds/lower CPU loads.
+powersave_bias: this parameter takes a value between 0 to 1000. It
+defines the percentage (times 10) value of the target frequency that
+will be shaved off of the target. For example, when set to 100 -- 10%,
+when ondemand governor would have targeted 1000 MHz, it will target
+1000 MHz - (10% of 1000 MHz) = 900 MHz instead. This is set to 0
+(disabled) by default.
+When AMD frequency sensitivity powersave bias driver --
+drivers/cpufreq/amd_freq_sensitivity.c is loaded, this parameter
+defines the workload frequency sensitivity threshold in which a lower
+frequency is chosen instead of ondemand governor's original target.
+The frequency sensitivity is a hardware reported (on AMD Family 16h
+Processors and above) value between 0 to 100% that tells software how
+the performance of the workload running on a CPU will change when
+frequency changes. A workload with sensitivity of 0% (memory/IO-bound)
+will not perform any better on higher core frequency, whereas a
+workload with sensitivity of 100% (CPU-bound) will perform better
+higher the frequency. When the driver is loaded, this is set to 400
+by default -- for CPUs running workloads with sensitivity value below
+40%, a lower frequency is chosen. Unloading the driver or writing 0
+will disable this feature.
+
2.5 Conservative
----------------
diff --git a/arch/x86/include/asm/cpufeature.h b/arch/x86/include/asm/cpufeature.h
index 93fe929..9e22520 100644
--- a/arch/x86/include/asm/cpufeature.h
+++ b/arch/x86/include/asm/cpufeature.h
@@ -182,6 +182,7 @@
#define X86_FEATURE_PTS (7*32+ 6) /* Intel Package Thermal Status */
#define X86_FEATURE_DTHERM (7*32+ 7) /* Digital Thermal Sensor */
#define X86_FEATURE_HW_PSTATE (7*32+ 8) /* AMD HW-PState */
+#define X86_FEATURE_PROC_FEEDBACK (7*32+ 9) /* AMD ProcFeedbackInterface */
/* Virtualization flags: Linux defined, word 8 */
#define X86_FEATURE_TPR_SHADOW (8*32+ 0) /* Intel TPR Shadow */
diff --git a/arch/x86/kernel/cpu/scattered.c b/arch/x86/kernel/cpu/scattered.c
index ee8e9ab..d92b5da 100644
--- a/arch/x86/kernel/cpu/scattered.c
+++ b/arch/x86/kernel/cpu/scattered.c
@@ -39,8 +39,9 @@
{ X86_FEATURE_APERFMPERF, CR_ECX, 0, 0x00000006, 0 },
{ X86_FEATURE_EPB, CR_ECX, 3, 0x00000006, 0 },
{ X86_FEATURE_XSAVEOPT, CR_EAX, 0, 0x0000000d, 1 },
- { X86_FEATURE_CPB, CR_EDX, 9, 0x80000007, 0 },
{ X86_FEATURE_HW_PSTATE, CR_EDX, 7, 0x80000007, 0 },
+ { X86_FEATURE_CPB, CR_EDX, 9, 0x80000007, 0 },
+ { X86_FEATURE_PROC_FEEDBACK, CR_EDX,11, 0x80000007, 0 },
{ X86_FEATURE_NPT, CR_EDX, 0, 0x8000000a, 0 },
{ X86_FEATURE_LBRV, CR_EDX, 1, 0x8000000a, 0 },
{ X86_FEATURE_SVML, CR_EDX, 2, 0x8000000a, 0 },
diff --git a/drivers/cpufreq/Kconfig.x86 b/drivers/cpufreq/Kconfig.x86
index d7dc0ed..2b8a8c3 100644
--- a/drivers/cpufreq/Kconfig.x86
+++ b/drivers/cpufreq/Kconfig.x86
@@ -129,6 +129,23 @@
For details, take a look at <file:Documentation/cpu-freq/>.
+config X86_AMD_FREQ_SENSITIVITY
+ tristate "AMD frequency sensitivity feedback powersave bias"
+ depends on CPU_FREQ_GOV_ONDEMAND && X86_ACPI_CPUFREQ && CPU_SUP_AMD
+ help
+ This adds AMD-specific powersave bias function to the ondemand
+ governor, which allows it to make more power-conscious frequency
+ change decisions based on feedback from hardware (availble on AMD
+ Family 16h and above).
+
+ Hardware feedback tells software how "sensitive" to frequency changes
+ the CPUs' workloads are. CPU-bound workloads will be more sensitive
+ -- they will perform better as frequency increases. Memory/IO-bound
+ workloads will be less sensitive -- they will not necessarily perform
+ better as frequency increases.
+
+ If in doubt, say N.
+
config X86_GX_SUSPMOD
tristate "Cyrix MediaGX/NatSemi Geode Suspend Modulation"
depends on X86_32 && PCI
diff --git a/drivers/cpufreq/Makefile b/drivers/cpufreq/Makefile
index 17417c7..a264dd3 100644
--- a/drivers/cpufreq/Makefile
+++ b/drivers/cpufreq/Makefile
@@ -41,6 +41,7 @@
obj-$(CONFIG_X86_P4_CLOCKMOD) += p4-clockmod.o
obj-$(CONFIG_X86_CPUFREQ_NFORCE2) += cpufreq-nforce2.o
obj-$(CONFIG_X86_INTEL_PSTATE) += intel_pstate.o
+obj-$(CONFIG_X86_AMD_FREQ_SENSITIVITY) += amd_freq_sensitivity.o
##################################################################################
# ARM SoC drivers
diff --git a/drivers/cpufreq/amd_freq_sensitivity.c b/drivers/cpufreq/amd_freq_sensitivity.c
new file mode 100644
index 0000000..f6b79ab
--- /dev/null
+++ b/drivers/cpufreq/amd_freq_sensitivity.c
@@ -0,0 +1,148 @@
+/*
+ * amd_freq_sensitivity.c: AMD frequency sensitivity feedback powersave bias
+ * for the ondemand governor.
+ *
+ * Copyright (C) 2013 Advanced Micro Devices, Inc.
+ *
+ * Author: Jacob Shin <jacob.shin@amd.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/types.h>
+#include <linux/percpu-defs.h>
+#include <linux/init.h>
+#include <linux/mod_devicetable.h>
+
+#include <asm/msr.h>
+#include <asm/cpufeature.h>
+
+#include "cpufreq_governor.h"
+
+#define MSR_AMD64_FREQ_SENSITIVITY_ACTUAL 0xc0010080
+#define MSR_AMD64_FREQ_SENSITIVITY_REFERENCE 0xc0010081
+#define CLASS_CODE_SHIFT 56
+#define POWERSAVE_BIAS_MAX 1000
+#define POWERSAVE_BIAS_DEF 400
+
+struct cpu_data_t {
+ u64 actual;
+ u64 reference;
+ unsigned int freq_prev;
+};
+
+static DEFINE_PER_CPU(struct cpu_data_t, cpu_data);
+
+static unsigned int amd_powersave_bias_target(struct cpufreq_policy *policy,
+ unsigned int freq_next,
+ unsigned int relation)
+{
+ int sensitivity;
+ long d_actual, d_reference;
+ struct msr actual, reference;
+ struct cpu_data_t *data = &per_cpu(cpu_data, policy->cpu);
+ struct dbs_data *od_data = policy->governor_data;
+ struct od_dbs_tuners *od_tuners = od_data->tuners;
+ struct od_cpu_dbs_info_s *od_info =
+ od_data->cdata->get_cpu_dbs_info_s(policy->cpu);
+
+ if (!od_info->freq_table)
+ return freq_next;
+
+ rdmsr_on_cpu(policy->cpu, MSR_AMD64_FREQ_SENSITIVITY_ACTUAL,
+ &actual.l, &actual.h);
+ rdmsr_on_cpu(policy->cpu, MSR_AMD64_FREQ_SENSITIVITY_REFERENCE,
+ &reference.l, &reference.h);
+ actual.h &= 0x00ffffff;
+ reference.h &= 0x00ffffff;
+
+ /* counter wrapped around, so stay on current frequency */
+ if (actual.q < data->actual || reference.q < data->reference) {
+ freq_next = policy->cur;
+ goto out;
+ }
+
+ d_actual = actual.q - data->actual;
+ d_reference = reference.q - data->reference;
+
+ /* divide by 0, so stay on current frequency as well */
+ if (d_reference == 0) {
+ freq_next = policy->cur;
+ goto out;
+ }
+
+ sensitivity = POWERSAVE_BIAS_MAX -
+ (POWERSAVE_BIAS_MAX * (d_reference - d_actual) / d_reference);
+
+ clamp(sensitivity, 0, POWERSAVE_BIAS_MAX);
+
+ /* this workload is not CPU bound, so choose a lower freq */
+ if (sensitivity < od_tuners->powersave_bias) {
+ if (data->freq_prev == policy->cur)
+ freq_next = policy->cur;
+
+ if (freq_next > policy->cur)
+ freq_next = policy->cur;
+ else if (freq_next < policy->cur)
+ freq_next = policy->min;
+ else {
+ unsigned int index;
+
+ cpufreq_frequency_table_target(policy,
+ od_info->freq_table, policy->cur - 1,
+ CPUFREQ_RELATION_H, &index);
+ freq_next = od_info->freq_table[index].frequency;
+ }
+
+ data->freq_prev = freq_next;
+ } else
+ data->freq_prev = 0;
+
+out:
+ data->actual = actual.q;
+ data->reference = reference.q;
+ return freq_next;
+}
+
+static int __init amd_freq_sensitivity_init(void)
+{
+ u64 val;
+
+ if (boot_cpu_data.x86_vendor != X86_VENDOR_AMD)
+ return -ENODEV;
+
+ if (!static_cpu_has(X86_FEATURE_PROC_FEEDBACK))
+ return -ENODEV;
+
+ if (rdmsrl_safe(MSR_AMD64_FREQ_SENSITIVITY_ACTUAL, &val))
+ return -ENODEV;
+
+ if (!(val >> CLASS_CODE_SHIFT))
+ return -ENODEV;
+
+ od_register_powersave_bias_handler(amd_powersave_bias_target,
+ POWERSAVE_BIAS_DEF);
+ return 0;
+}
+late_initcall(amd_freq_sensitivity_init);
+
+static void __exit amd_freq_sensitivity_exit(void)
+{
+ od_unregister_powersave_bias_handler();
+}
+module_exit(amd_freq_sensitivity_exit);
+
+static const struct x86_cpu_id amd_freq_sensitivity_ids[] = {
+ X86_FEATURE_MATCH(X86_FEATURE_PROC_FEEDBACK),
+ {}
+};
+MODULE_DEVICE_TABLE(x86cpu, amd_freq_sensitivity_ids);
+
+MODULE_AUTHOR("Jacob Shin <jacob.shin@amd.com>");
+MODULE_DESCRIPTION("AMD frequency sensitivity feedback powersave bias for "
+ "the ondemand governor.");
+MODULE_LICENSE("GPL");