Commit 9522a2ff authored by Srinivas Pandruvada's avatar Srinivas Pandruvada Committed by Rafael J. Wysocki

cpufreq: intel_pstate: Enforce _PPC limits

Use ACPI _PPC notification to limit max P state driver will request.
ACPI _PPC change notification is sent by BIOS to limit max P state
in several cases:
- Reduce impact of platform thermal condition
- When Config TDP feature is used, a changed _PPC is sent to
follow TDP change
- Remote node managers in server want to control platform power
via baseboard management controller (BMC)

This change registers with ACPI processor performance lib so that
_PPC changes are notified to cpufreq core, which in turns will
result in call to .setpolicy() callback. Also the way _PSS
table identifies a turbo frequency is not compatible to max turbo
frequency in intel_pstate, so the very first entry in _PSS needs
to be adjusted.

This feature can be turned on by using kernel parameters:
Signed-off-by: default avatarSrinivas Pandruvada <>
[ rjw: Minor cleanups ]
Signed-off-by: default avatarRafael J. Wysocki <>
parent eaa2c3ae
......@@ -1661,6 +1661,8 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
Only load intel_pstate on systems which support
hardware P state control (HWP) if available.
Enforce ACPI _PPC performance limits.
intremap= [X86-64, Intel-IOMMU]
on enable Interrupt Remapping (default)
......@@ -5,6 +5,7 @@
bool "Intel P state control"
depends on X86
This driver provides a P state for Intel core processors.
The driver implements an internal governor and will become
......@@ -41,6 +41,10 @@
#define ATOM_TURBO_RATIOS 0x66c
#define ATOM_TURBO_VIDS 0x66d
#include <acpi/processor.h>
#define FRAC_BITS 8
#define int_tofp(X) ((int64_t)(X) << FRAC_BITS)
#define fp_toint(X) ((X) >> FRAC_BITS)
......@@ -174,6 +178,8 @@ struct _pid {
* @prev_cummulative_iowait: IO Wait time difference from last and
* current sample
* @sample: Storage for storing last Sample data
* @acpi_perf_data: Stores ACPI perf information read from _PSS
* @valid_pss_table: Set to true for valid ACPI _PSS entries found
* This structure stores per CPU instance data for all CPUs.
......@@ -192,6 +198,10 @@ struct cpudata {
u64 prev_tsc;
u64 prev_cummulative_iowait;
struct sample sample;
struct acpi_processor_performance acpi_perf_data;
bool valid_pss_table;
static struct cpudata **all_cpu_data;
......@@ -260,6 +270,9 @@ static struct pstate_adjust_policy pid_params;
static struct pstate_funcs pstate_funcs;
static int hwp_active;
static bool acpi_ppc;
* struct perf_limits - Store user and policy limits
......@@ -333,6 +346,111 @@ static struct perf_limits *limits = &performance_limits;
static struct perf_limits *limits = &powersave_limits;
* The max target pstate ratio is a 8 bit value in both PLATFORM_INFO MSR and
* in TURBO_RATIO_LIMIT MSR, which pstate driver stores in max_pstate and
* max_turbo_pstate fields. The PERF_CTL MSR contains 16 bit value for P state
* ratio, out of it only high 8 bits are used. For example 0x1700 is setting
* target ratio 0x17. The _PSS control value stores in a format which can be
* directly written to PERF_CTL MSR. But in intel_pstate driver this shift
* occurs during write to PERF_CTL (E.g. for cores core_set_pstate()).
* This function converts the _PSS control value to intel pstate driver format
* for comparison and assignment.
static int convert_to_native_pstate_format(struct cpudata *cpu, int index)
return cpu->acpi_perf_data.states[index].control >> 8;
static void intel_pstate_init_acpi_perf_limits(struct cpufreq_policy *policy)
struct cpudata *cpu;
int turbo_pss_ctl;
int ret;
int i;
if (!acpi_ppc)
cpu = all_cpu_data[policy->cpu];
ret = acpi_processor_register_performance(&cpu->acpi_perf_data,
if (ret)
* Check if the control value in _PSS is for PERF_CTL MSR, which should
* guarantee that the states returned by it map to the states in our
* list directly.
if (cpu->acpi_perf_data.control_register.space_id !=
goto err;
* If there is only one entry _PSS, simply ignore _PSS and continue as
* usual without taking _PSS into account
if (cpu->acpi_perf_data.state_count < 2)
goto err;
pr_debug("CPU%u - ACPI _PSS perf data\n", policy->cpu);
for (i = 0; i < cpu->acpi_perf_data.state_count; i++) {
pr_debug(" %cP%d: %u MHz, %u mW, 0x%x\n",
(i == cpu->acpi_perf_data.state ? '*' : ' '), i,
(u32) cpu->acpi_perf_data.states[i].core_frequency,
(u32) cpu->acpi_perf_data.states[i].power,
(u32) cpu->acpi_perf_data.states[i].control);
* The _PSS table doesn't contain whole turbo frequency range.
* This just contains +1 MHZ above the max non turbo frequency,
* with control value corresponding to max turbo ratio. But
* when cpufreq set policy is called, it will call with this
* max frequency, which will cause a reduced performance as
* this driver uses real max turbo frequency as the max
* frequency. So correct this frequency in _PSS table to
* correct max turbo frequency based on the turbo ratio.
* Also need to convert to MHz as _PSS freq is in MHz.
turbo_pss_ctl = convert_to_native_pstate_format(cpu, 0);
if (turbo_pss_ctl > cpu->pstate.max_pstate)
cpu->acpi_perf_data.states[0].core_frequency =
policy->cpuinfo.max_freq / 1000;
cpu->valid_pss_table = true;
pr_info("_PPC limits will be enforced\n");
cpu->valid_pss_table = false;
static void intel_pstate_exit_perf_limits(struct cpufreq_policy *policy)
struct cpudata *cpu;
cpu = all_cpu_data[policy->cpu];
if (!cpu->valid_pss_table)
static void intel_pstate_init_acpi_perf_limits(struct cpufreq_policy *policy)
static void intel_pstate_exit_perf_limits(struct cpufreq_policy *policy)
static inline void pid_reset(struct _pid *pid, int setpoint, int busy,
int deadband, int integral) {
pid->setpoint = int_tofp(setpoint);
......@@ -1398,18 +1516,27 @@ static int intel_pstate_cpu_init(struct cpufreq_policy *policy)
policy->cpuinfo.min_freq = cpu->pstate.min_pstate * cpu->pstate.scaling;
policy->cpuinfo.max_freq =
cpu->pstate.turbo_pstate * cpu->pstate.scaling;
policy->cpuinfo.transition_latency = CPUFREQ_ETERNAL;
cpumask_set_cpu(policy->cpu, policy->cpus);
return 0;
static int intel_pstate_cpu_exit(struct cpufreq_policy *policy)
return 0;
static struct cpufreq_driver intel_pstate_driver = {
.verify = intel_pstate_verify_policy,
.setpolicy = intel_pstate_set_policy,
.get = intel_pstate_get,
.init = intel_pstate_cpu_init,
.exit = intel_pstate_cpu_exit,
.stop_cpu = intel_pstate_stop_cpu,
.name = "intel_pstate",
......@@ -1453,8 +1580,7 @@ static void copy_cpu_funcs(struct pstate_funcs *funcs)
#include <acpi/processor.h>
static bool intel_pstate_no_acpi_pss(void)
......@@ -1660,6 +1786,12 @@ static int __init intel_pstate_setup(char *str)
force_load = 1;
if (!strcmp(str, "hwp_only"))
hwp_only = 1;
if (!strcmp(str, "support_acpi_ppc"))
acpi_ppc = true;
return 0;
early_param("intel_pstate", intel_pstate_setup);
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