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cpufreq: intel_pstate: Generic governors support 

There may be reasons to use generic cpufreq governors (eg. schedutil)
on Intel platforms instead of the intel_pstate driver's internal
governor.  However, that currently can only be done by disabling
intel_pstate altogether and using the acpi-cpufreq driver instead
of it, which is subject to limitations.

First of all, acpi-cpufreq only works on systems where the _PSS
object is present in the ACPI tables for all logical CPUs.  Second,
on those systems acpi-cpufreq will only use frequencies listed by
_PSS which may be suboptimal.  In particular, by convention, the
whole turbo range is represented in _PSS as a single P-state and
the frequency assigned to it is greater by 1 MHz than the greatest
non-turbo frequency listed by _PSS.  That may confuse governors to
use turbo frequencies less frequently which may lead to suboptimal
performance.

For this reason, make it possible to use the intel_pstate driver
with generic cpufreq governors as a "normal" cpufreq driver.  That
mode is enforced by adding intel_pstate=passive to the kernel
command line and cannot be disabled at run time.  In that mode,
intel_pstate provides a cpufreq driver interface including
the ->target() and ->fast_switch() callbacks and is listed in
scaling_driver as "intel_cpufreq".

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Tested-by: Doug Smythies <dsmythies@telus.net>
This commit is contained in:
Rafael J. Wysocki 2016-11-17 23:34:17 +01:00
parent d0ea59e188
commit 001c76f05b
2 changed files with 181 additions and 29 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

6
Documentation/kernel-parameters.txt
View File

@ -1760,6 +1760,12 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
disable
Do not enable intel_pstate as the default
scaling driver for the supported processors
passive
Use intel_pstate as a scaling driver, but configure it
to work with generic cpufreq governors (instead of
enabling its internal governor). This mode cannot be
used along with the hardware-managed P-states (HWP)
feature.
force
Enable intel_pstate on systems that prohibit it by default
in favor of acpi-cpufreq. Forcing the intel_pstate driver

204
drivers/cpufreq/intel_pstate.c
View File

@ -37,6 +37,8 @@
#include <asm/cpufeature.h>
#include <asm/intel-family.h>
#define INTEL_CPUFREQ_TRANSITION_LATENCY 20000
#define ATOM_RATIOS 0x66a
#define ATOM_VIDS 0x66b
#define ATOM_TURBO_RATIOS 0x66c
@ -122,6 +124,8 @@ struct sample {
* @scaling: Scaling factor to convert frequency to cpufreq
* frequency units
* @turbo_pstate: Max Turbo P state possible for this platform
* @max_freq: @max_pstate frequency in cpufreq units
* @turbo_freq: @turbo_pstate frequency in cpufreq units
*
* Stores the per cpu model P state limits and current P state.
*/
@ -132,6 +136,8 @@ struct pstate_data {
int max_pstate_physical;
int scaling;
int turbo_pstate;
unsigned int max_freq;
unsigned int turbo_freq;
};
/**
@ -470,7 +476,7 @@ 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 int intel_pstate_exit_perf_limits(struct cpufreq_policy *policy)
{
}
#endif
@ -1225,6 +1231,8 @@ static void intel_pstate_get_cpu_pstates(struct cpudata *cpu)
cpu->pstate.max_pstate_physical = pstate_funcs.get_max_physical();
cpu->pstate.turbo_pstate = pstate_funcs.get_turbo();
cpu->pstate.scaling = pstate_funcs.get_scaling();
cpu->pstate.max_freq = cpu->pstate.max_pstate * cpu->pstate.scaling;
cpu->pstate.turbo_freq = cpu->pstate.turbo_pstate * cpu->pstate.scaling;
if (pstate_funcs.get_vid)
pstate_funcs.get_vid(cpu);
@ -1363,15 +1371,19 @@ static inline int32_t get_target_pstate_use_performance(struct cpudata *cpu)
return cpu->pstate.current_pstate - pid_calc(&cpu->pid, perf_scaled);
}
static inline void intel_pstate_update_pstate(struct cpudata *cpu, int pstate)
static int intel_pstate_prepare_request(struct cpudata *cpu, int pstate)
{
int max_perf, min_perf;
update_turbo_state();
intel_pstate_get_min_max(cpu, &min_perf, &max_perf);
pstate = clamp_t(int, pstate, min_perf, max_perf);
trace_cpu_frequency(pstate * cpu->pstate.scaling, cpu->cpu);
return pstate;
}
static void intel_pstate_update_pstate(struct cpudata *cpu, int pstate)
{
pstate = intel_pstate_prepare_request(cpu, pstate);
if (pstate == cpu->pstate.current_pstate)
return;
@ -1389,6 +1401,8 @@ static inline void intel_pstate_adjust_busy_pstate(struct cpudata *cpu)
target_pstate = cpu->policy == CPUFREQ_POLICY_PERFORMANCE ?
cpu->pstate.turbo_pstate : pstate_funcs.get_target_pstate(cpu);
update_turbo_state();
intel_pstate_update_pstate(cpu, target_pstate);
sample = &cpu->sample;
@ -1670,22 +1684,30 @@ static int intel_pstate_verify_policy(struct cpufreq_policy *policy)
return 0;
}
static void intel_pstate_stop_cpu(struct cpufreq_policy *policy)
static void intel_cpufreq_stop_cpu(struct cpufreq_policy *policy)
{
int cpu_num = policy->cpu;
struct cpudata *cpu = all_cpu_data[cpu_num];
pr_debug("CPU %d exiting\n", cpu_num);
intel_pstate_clear_update_util_hook(cpu_num);
if (hwp_active)
return;
intel_pstate_set_min_pstate(cpu);
intel_pstate_set_min_pstate(all_cpu_data[policy->cpu]);
}
static int intel_pstate_cpu_init(struct cpufreq_policy *policy)
static void intel_pstate_stop_cpu(struct cpufreq_policy *policy)
{
pr_debug("CPU %d exiting\n", policy->cpu);
intel_pstate_clear_update_util_hook(policy->cpu);
if (!hwp_active)
intel_cpufreq_stop_cpu(policy);
}
static int intel_pstate_cpu_exit(struct cpufreq_policy *policy)
{
intel_pstate_exit_perf_limits(policy);
policy->fast_switch_possible = false;
return 0;
}
static int __intel_pstate_cpu_init(struct cpufreq_policy *policy)
{
struct cpudata *cpu;
int rc;
@ -1696,11 +1718,6 @@ static int intel_pstate_cpu_init(struct cpufreq_policy *policy)
cpu = all_cpu_data[policy->cpu];
if (limits->min_perf_pct == 100 && limits->max_perf_pct == 100)
policy->policy = CPUFREQ_POLICY_PERFORMANCE;
else
policy->policy = CPUFREQ_POLICY_POWERSAVE;
/*
* We need sane value in the cpu->perf_limits, so inherit from global
* perf_limits limits, which are seeded with values based on the
@ -1720,20 +1737,30 @@ static int intel_pstate_cpu_init(struct cpufreq_policy *policy)
policy->cpuinfo.max_freq *= cpu->pstate.scaling;
intel_pstate_init_acpi_perf_limits(policy);
policy->cpuinfo.transition_latency = CPUFREQ_ETERNAL;
cpumask_set_cpu(policy->cpu, policy->cpus);
policy->fast_switch_possible = true;
return 0;
}
static int intel_pstate_cpu_exit(struct cpufreq_policy *policy)
static int intel_pstate_cpu_init(struct cpufreq_policy *policy)
{
intel_pstate_exit_perf_limits(policy);
int ret = __intel_pstate_cpu_init(policy);
if (ret)
return ret;
policy->cpuinfo.transition_latency = CPUFREQ_ETERNAL;
if (limits->min_perf_pct == 100 && limits->max_perf_pct == 100)
policy->policy = CPUFREQ_POLICY_PERFORMANCE;
else
policy->policy = CPUFREQ_POLICY_POWERSAVE;
return 0;
}
static struct cpufreq_driver intel_pstate_driver = {
static struct cpufreq_driver intel_pstate = {
.flags = CPUFREQ_CONST_LOOPS,
.verify = intel_pstate_verify_policy,
.setpolicy = intel_pstate_set_policy,
@ -1745,6 +1772,118 @@ static struct cpufreq_driver intel_pstate_driver = {
.name = "intel_pstate",
};
static int intel_cpufreq_verify_policy(struct cpufreq_policy *policy)
{
struct cpudata *cpu = all_cpu_data[policy->cpu];
struct perf_limits *perf_limits = limits;
update_turbo_state();
policy->cpuinfo.max_freq = limits->turbo_disabled ?
cpu->pstate.max_freq : cpu->pstate.turbo_freq;
cpufreq_verify_within_cpu_limits(policy);
if (per_cpu_limits)
perf_limits = cpu->perf_limits;
intel_pstate_update_perf_limits(policy, perf_limits);
return 0;
}
static unsigned int intel_cpufreq_turbo_update(struct cpudata *cpu,
struct cpufreq_policy *policy,
unsigned int target_freq)
{
unsigned int max_freq;
update_turbo_state();
max_freq = limits->no_turbo || limits->turbo_disabled ?
cpu->pstate.max_freq : cpu->pstate.turbo_freq;
policy->cpuinfo.max_freq = max_freq;
if (policy->max > max_freq)
policy->max = max_freq;
if (target_freq > max_freq)
target_freq = max_freq;
return target_freq;
}
static int intel_cpufreq_target(struct cpufreq_policy *policy,
unsigned int target_freq,
unsigned int relation)
{
struct cpudata *cpu = all_cpu_data[policy->cpu];
struct cpufreq_freqs freqs;
int target_pstate;
freqs.old = policy->cur;
freqs.new = intel_cpufreq_turbo_update(cpu, policy, target_freq);
cpufreq_freq_transition_begin(policy, &freqs);
switch (relation) {
case CPUFREQ_RELATION_L:
target_pstate = DIV_ROUND_UP(freqs.new, cpu->pstate.scaling);
break;
case CPUFREQ_RELATION_H:
target_pstate = freqs.new / cpu->pstate.scaling;
break;
default:
target_pstate = DIV_ROUND_CLOSEST(freqs.new, cpu->pstate.scaling);
break;
}
target_pstate = intel_pstate_prepare_request(cpu, target_pstate);
if (target_pstate != cpu->pstate.current_pstate) {
cpu->pstate.current_pstate = target_pstate;
wrmsrl_on_cpu(policy->cpu, MSR_IA32_PERF_CTL,
pstate_funcs.get_val(cpu, target_pstate));
}
cpufreq_freq_transition_end(policy, &freqs, false);
return 0;
}
static unsigned int intel_cpufreq_fast_switch(struct cpufreq_policy *policy,
unsigned int target_freq)
{
struct cpudata *cpu = all_cpu_data[policy->cpu];
int target_pstate;
target_freq = intel_cpufreq_turbo_update(cpu, policy, target_freq);
target_pstate = DIV_ROUND_UP(target_freq, cpu->pstate.scaling);
intel_pstate_update_pstate(cpu, target_pstate);
return target_freq;
}
static int intel_cpufreq_cpu_init(struct cpufreq_policy *policy)
{
int ret = __intel_pstate_cpu_init(policy);
if (ret)
return ret;
policy->cpuinfo.transition_latency = INTEL_CPUFREQ_TRANSITION_LATENCY;
/* This reflects the intel_pstate_get_cpu_pstates() setting. */
policy->cur = policy->cpuinfo.min_freq;
return 0;
}
static struct cpufreq_driver intel_cpufreq = {
.flags = CPUFREQ_CONST_LOOPS,
.verify = intel_cpufreq_verify_policy,
.target = intel_cpufreq_target,
.fast_switch = intel_cpufreq_fast_switch,
.init = intel_cpufreq_cpu_init,
.exit = intel_pstate_cpu_exit,
.stop_cpu = intel_cpufreq_stop_cpu,
.name = "intel_cpufreq",
};
static struct cpufreq_driver *intel_pstate_driver = &intel_pstate;
static int no_load __initdata;
static int no_hwp __initdata;
static int hwp_only __initdata;
@ -1976,7 +2115,7 @@ hwp_cpu_matched:
intel_pstate_request_control_from_smm();
rc = cpufreq_register_driver(&intel_pstate_driver);
rc = cpufreq_register_driver(intel_pstate_driver);
if (rc)
goto out;
@ -1991,7 +2130,9 @@ out:
get_online_cpus();
for_each_online_cpu(cpu) {
if (all_cpu_data[cpu]) {
intel_pstate_clear_update_util_hook(cpu);
if (intel_pstate_driver == &intel_pstate)
intel_pstate_clear_update_util_hook(cpu);
kfree(all_cpu_data[cpu]);
}
}
@ -2007,8 +2148,13 @@ static int __init intel_pstate_setup(char *str)
if (!str)
return -EINVAL;
if (!strcmp(str, "disable"))
if (!strcmp(str, "disable")) {
no_load = 1;
} else if (!strcmp(str, "passive")) {
pr_info("Passive mode enabled\n");
intel_pstate_driver = &intel_cpufreq;
no_hwp = 1;
}
if (!strcmp(str, "no_hwp")) {
pr_info("HWP disabled\n");
no_hwp = 1;