Operation Modes
===============
-``intel_pstate`` can operate in three different modes: in the active mode with
-or without hardware-managed P-states support and in the passive mode. Which of
-them will be in effect depends on what kernel command line options are used and
-on the capabilities of the processor.
+``intel_pstate`` can operate in two different modes, active or passive. In the
+active mode, it uses its own internal performance scaling governor algorithm or
+allows the hardware to do preformance scaling by itself, while in the passive
+mode it responds to requests made by a generic ``CPUFreq`` governor implementing
+a certain performance scaling algorithm. Which of them will be in effect
+depends on what kernel command line options are used and on the capabilities of
+the processor.
Active Mode
-----------
hardware-managed P-states (HWP) support. It is always used if the
``intel_pstate=passive`` argument is passed to the kernel in the command line
regardless of whether or not the given processor supports HWP. [Note that the
-``intel_pstate=no_hwp`` setting implies ``intel_pstate=passive`` if it is used
-without ``intel_pstate=active``.] Like in the active mode without HWP support,
-in this mode ``intel_pstate`` may refuse to work with processors that are not
-recognized by it.
+``intel_pstate=no_hwp`` setting causes the driver to start in the passive mode
+if it is not combined with ``intel_pstate=active``.] Like in the active mode
+without HWP support, in this mode ``intel_pstate`` may refuse to work with
+processors that are not recognized by it if HWP is prevented from being enabled
+through the kernel command line.
If the driver works in this mode, the ``scaling_driver`` policy attribute in
``sysfs`` for all ``CPUFreq`` policies contains the string "intel_cpufreq".
For this reason, there is a list of supported processors in ``intel_pstate`` and
the driver initialization will fail if the detected processor is not in that
-list, unless it supports the `HWP feature <Active Mode_>`_. [The interface to
-obtain all of the information listed above is the same for all of the processors
-supporting the HWP feature, which is why they all are supported by
-``intel_pstate``.]
+list, unless it supports the HWP feature. [The interface to obtain all of the
+information listed above is the same for all of the processors supporting the
+HWP feature, which is why ``intel_pstate`` works with all of them.]
User Space Interface in ``sysfs``
as well as the per-policy ones) are then reset to their default
values, possibly depending on the target operation mode.]
- That only is supported in some configurations, though (for example, if
- the `HWP feature is enabled in the processor <Active Mode With HWP_>`_,
- the operation mode of the driver cannot be changed), and if it is not
- supported in the current configuration, writes to this attribute will
- fail with an appropriate error.
-
``energy_efficiency``
- This attribute is only present on platforms, which have CPUs matching
- Kaby Lake or Coffee Lake desktop CPU model. By default
- energy efficiency optimizations are disabled on these CPU models in HWP
- mode by this driver. Enabling energy efficiency may limit maximum
- operating frequency in both HWP and non HWP mode. In non HWP mode,
- optimizations are done only in the turbo frequency range. In HWP mode,
- optimizations are done in the entire frequency range. Setting this
- attribute to "1" enables energy efficiency optimizations and setting
- to "0" disables energy efficiency optimizations.
+ This attribute is only present on platforms with CPUs matching the Kaby
+ Lake or Coffee Lake desktop CPU model. By default, energy-efficiency
+ optimizations are disabled on these CPU models if HWP is enabled.
+ Enabling energy-efficiency optimizations may limit maximum operating
+ frequency with or without the HWP feature. With HWP enabled, the
+ optimizations are done only in the turbo frequency range. Without it,
+ they are done in the entire available frequency range. Setting this
+ attribute to "1" enables the energy-efficiency optimizations and setting
+ to "0" disables them.
Interpretation of Policy Attributes
-----------------------------------
policy for the time interval between the last two invocations of the
driver's utilization update callback by the CPU scheduler for that CPU.
-One more policy attribute is present if the `HWP feature is enabled in the
-processor <Active Mode With HWP_>`_:
+One more policy attribute is present if the HWP feature is enabled in the
+processor:
``base_frequency``
Shows the base frequency of the CPU. Any frequency above this will be
3. The global and per-policy limits can be set independently.
-I
f the `HWP feature is enabled in the processor <Active Mode With HWP_>`_, the
-resulting effective values are written into its registers whenever the limits
-change in order to request its internal P-state selection logic to always set
-P-states within these limits. Otherwise, the limits are taken into account by
-scaling governors (in the `passive mode <Passive Mode_>`_) and by the driver
+I
n the `active mode with the HWP feature enabled <Active Mode With HWP_>`_, the
+resulting effective values are written into hardware registers whenever the
+limits change in order to request its internal P-state selection logic to always
+set P-states within these limits. Otherwise, the limits are taken into account
+
by scaling governors (in the `passive mode <Passive Mode_>`_) and by the driver
every time before setting a new P-state for a CPU.
Additionally, if the ``intel_pstate=per_cpu_perf_limits`` command line argument
Energy vs Performance Hints
---------------------------
-If ``intel_pstate`` works in the `active mode with the HWP feature enabled
-<Active Mode With HWP_>`_ in the processor, additional attributes are present
-in every ``CPUFreq`` policy directory in ``sysfs``. They are intended to allow
-user space to help ``intel_pstate`` to adjust the processor's internal P-state
-selection logic by focusing it on performance or on energy-efficiency, or
-somewhere between the two extremes:
+If the hardware-managed P-states (HWP) is enabled in the processor, additional
+attributes, intended to allow user space to help ``intel_pstate`` to adjust the
+processor's internal P-state selection logic by focusing it on performance or on
+energy-efficiency, or somewhere between the two extremes, are present in every
+``CPUFreq`` policy directory in ``sysfs``. They are :
``energy_performance_preference``
Current value of the energy vs performance hint for the given policy
Do not register ``intel_pstate`` as the scaling driver even if the
processor is supported by it.
+``active``
+ Register ``intel_pstate`` in the `active mode <Active Mode_>`_ to start
+ with.
+
``passive``
Register ``intel_pstate`` in the `passive mode <Passive Mode_>`_ to
start with.
- This option implies the ``no_hwp`` one described below.
-
``force``
Register ``intel_pstate`` as the scaling driver instead of
``acpi-cpufreq`` even if the latter is preferred on the given system.
driver is used instead of ``acpi-cpufreq``.
``no_hwp``
- Do not enable the `hardware-managed P-states (HWP) feature
- <Active Mode With HWP_>`_ even if it is supported by the processor.
+ Do not enable the hardware-managed P-states (HWP) feature even if it is
+ supported by the processor.
``hwp_only``
Register ``intel_pstate`` as the scaling driver only if the
- `hardware-managed P-states (HWP) feature <Active Mode With HWP_>`_ is
- supported by the processor.
+ hardware-managed P-states (HWP) feature is supported by the processor.
``support_acpi_ppc``
Take ACPI ``_PPC`` performance limits into account.
#define INTEL_PSTATE_SAMPLING_INTERVAL (10 * NSEC_PER_MSEC)
#define INTEL_CPUFREQ_TRANSITION_LATENCY 20000
+#define INTEL_CPUFREQ_TRANSITION_DELAY_HWP 5000
#define INTEL_CPUFREQ_TRANSITION_DELAY 500
#ifdef CONFIG_ACPI
* preference/bias
* @epp_saved: Saved EPP/EPB during system suspend or CPU offline
* operation
+ * @epp_cached Cached HWP energy-performance preference value
* @hwp_req_cached: Cached value of the last HWP Request MSR
* @hwp_cap_cached: Cached value of the last HWP Capabilities MSR
* @last_io_update: Last time when IO wake flag was set
s16 epp_policy;
s16 epp_default;
s16 epp_saved;
+ s16 epp_cached;
u64 hwp_req_cached;
u64 hwp_cap_cached;
u64 last_io_update;
return index;
}
+static int intel_pstate_set_epp(struct cpudata *cpu, u32 epp)
+{
+ /*
+ * Use the cached HWP Request MSR value, because in the active mode the
+ * register itself may be updated by intel_pstate_hwp_boost_up() or
+ * intel_pstate_hwp_boost_down() at any time.
+ */
+ u64 value = READ_ONCE(cpu->hwp_req_cached);
+
+ value &= ~GENMASK_ULL(31, 24);
+ value |= (u64)epp << 24;
+ /*
+ * The only other updater of hwp_req_cached in the active mode,
+ * intel_pstate_hwp_set(), is called under the same lock as this
+ * function, so it cannot run in parallel with the update below.
+ */
+ WRITE_ONCE(cpu->hwp_req_cached, value);
+ return wrmsrl_on_cpu(cpu->cpu, MSR_HWP_REQUEST, value);
+}
+
static int intel_pstate_set_energy_pref_index(struct cpudata *cpu_data,
int pref_index, bool use_raw,
u32 raw_epp)
epp = cpu_data->epp_default;
if (boot_cpu_has(X86_FEATURE_HWP_EPP)) {
- /*
- * Use the cached HWP Request MSR value, because the register
- * itself may be updated by intel_pstate_hwp_boost_up() or
- * intel_pstate_hwp_boost_down() at any time.
- */
- u64 value = READ_ONCE(cpu_data->hwp_req_cached);
-
- value &= ~GENMASK_ULL(31, 24);
-
if (use_raw)
epp = raw_epp;
else if (epp == -EINVAL)
epp = epp_values[pref_index - 1];
- value |= (u64)epp << 24;
- /*
- * The only other updater of hwp_req_cached in the active mode,
- * intel_pstate_hwp_set(), is called under the same lock as this
- * function, so it cannot run in parallel with the update below.
- */
- WRITE_ONCE(cpu_data->hwp_req_cached, value);
- ret = wrmsrl_on_cpu(cpu_data->cpu, MSR_HWP_REQUEST, value);
+ ret = intel_pstate_set_epp(cpu_data, epp);
} else {
if (epp == -EINVAL)
epp = (pref_index - 1) << 2;
cpufreq_freq_attr_ro(energy_performance_available_preferences);
+static struct cpufreq_driver intel_pstate;
+
static ssize_t store_energy_performance_preference(
struct cpufreq_policy *policy, const char *buf, size_t count)
{
- struct cpudata *cpu_data = all_cpu_data[policy->cpu];
+ struct cpudata *cpu = all_cpu_data[policy->cpu];
char str_preference[21];
bool raw = false;
ssize_t ret;
raw = true;
}
+ /*
+ * This function runs with the policy R/W semaphore held, which
+ * guarantees that the driver pointer will not change while it is
+ * running.
+ */
+ if (!intel_pstate_driver)
+ return -EAGAIN;
+
mutex_lock(&intel_pstate_limits_lock);
- ret = intel_pstate_set_energy_pref_index(cpu_data, ret, raw, epp);
- if (!ret)
- ret = count;
+ if (intel_pstate_driver == &intel_pstate) {
+ ret = intel_pstate_set_energy_pref_index(cpu, ret, raw, epp);
+ } else {
+ /*
+ * In the passive mode the governor needs to be stopped on the
+ * target CPU before the EPP update and restarted after it,
+ * which is super-heavy-weight, so make sure it is worth doing
+ * upfront.
+ */
+ if (!raw)
+ epp = ret ? epp_values[ret - 1] : cpu->epp_default;
+
+ if (cpu->epp_cached != epp) {
+ int err;
+
+ cpufreq_stop_governor(policy);
+ ret = intel_pstate_set_epp(cpu, epp);
+ err = cpufreq_start_governor(policy);
+ if (!ret) {
+ cpu->epp_cached = epp;
+ ret = err;
+ }
+ }
+ }
mutex_unlock(&intel_pstate_limits_lock);
- return ret;
+ return ret ?: count;
}
static ssize_t show_energy_performance_preference(
return count;
}
-static struct cpufreq_driver intel_pstate;
-
static void update_qos_request(enum freq_qos_req_type type)
{
int max_state, turbo_max, freq, i, perf_pct;
static const struct x86_cpu_id intel_pstate_cpu_ee_disable_ids[];
+static struct kobject *intel_pstate_kobject;
+
static void __init intel_pstate_sysfs_expose_params(void)
{
- struct kobject *intel_pstate_kobject;
int rc;
intel_pstate_kobject = kobject_create_and_add("intel_pstate",
rc = sysfs_create_file(intel_pstate_kobject, &min_perf_pct.attr);
WARN_ON(rc);
- if (hwp_active) {
- rc = sysfs_create_file(intel_pstate_kobject,
- &hwp_dynamic_boost.attr);
- WARN_ON(rc);
- }
-
if (x86_match_cpu(intel_pstate_cpu_ee_disable_ids)) {
rc = sysfs_create_file(intel_pstate_kobject, &energy_efficiency.attr);
WARN_ON(rc);
}
}
+
+static void intel_pstate_sysfs_expose_hwp_dynamic_boost(void)
+{
+ int rc;
+
+ if (!hwp_active)
+ return;
+
+ rc = sysfs_create_file(intel_pstate_kobject, &hwp_dynamic_boost.attr);
+ WARN_ON_ONCE(rc);
+}
+
+static void intel_pstate_sysfs_hide_hwp_dynamic_boost(void)
+{
+ if (!hwp_active)
+ return;
+
+ sysfs_remove_file(intel_pstate_kobject, &hwp_dynamic_boost.attr);
+}
+
/************************** sysfs end ************************/
static void intel_pstate_hwp_enable(struct cpudata *cpudata)
static void intel_cpufreq_stop_cpu(struct cpufreq_policy *policy)
{
- intel_pstate_set_min_pstate(all_cpu_data[policy->cpu]);
+ if (hwp_active)
+ intel_pstate_hwp_force_min_perf(policy->cpu);
+ else
+ intel_pstate_set_min_pstate(all_cpu_data[policy->cpu]);
}
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) {
+ if (hwp_active)
intel_pstate_hwp_save_state(policy);
- intel_pstate_hwp_force_min_perf(policy->cpu);
- } else {
- intel_cpufreq_stop_cpu(policy);
- }
+
+ intel_cpufreq_stop_cpu(policy);
}
static int intel_pstate_cpu_exit(struct cpufreq_policy *policy)
fp_toint(cpu->iowait_boost * 100));
}
+static void intel_cpufreq_adjust_hwp(struct cpudata *cpu, u32 target_pstate,
+ bool fast_switch)
+{
+ u64 prev = READ_ONCE(cpu->hwp_req_cached), value = prev;
+
+ value &= ~HWP_MIN_PERF(~0L);
+ value |= HWP_MIN_PERF(target_pstate);
+
+ /*
+ * The entire MSR needs to be updated in order to update the HWP min
+ * field in it, so opportunistically update the max too if needed.
+ */
+ value &= ~HWP_MAX_PERF(~0L);
+ value |= HWP_MAX_PERF(cpu->max_perf_ratio);
+
+ if (value == prev)
+ return;
+
+ WRITE_ONCE(cpu->hwp_req_cached, value);
+ if (fast_switch)
+ wrmsrl(MSR_HWP_REQUEST, value);
+ else
+ wrmsrl_on_cpu(cpu->cpu, MSR_HWP_REQUEST, value);
+}
+
+static void intel_cpufreq_adjust_perf_ctl(struct cpudata *cpu,
+ u32 target_pstate, bool fast_switch)
+{
+ if (fast_switch)
+ wrmsrl(MSR_IA32_PERF_CTL,
+ pstate_funcs.get_val(cpu, target_pstate));
+ else
+ wrmsrl_on_cpu(cpu->cpu, MSR_IA32_PERF_CTL,
+ pstate_funcs.get_val(cpu, target_pstate));
+}
+
+static int intel_cpufreq_update_pstate(struct cpudata *cpu, int target_pstate,
+ bool fast_switch)
+{
+ int old_pstate = cpu->pstate.current_pstate;
+
+ target_pstate = intel_pstate_prepare_request(cpu, target_pstate);
+ if (target_pstate != old_pstate) {
+ cpu->pstate.current_pstate = target_pstate;
+ if (hwp_active)
+ intel_cpufreq_adjust_hwp(cpu, target_pstate,
+ fast_switch);
+ else
+ intel_cpufreq_adjust_perf_ctl(cpu, target_pstate,
+ fast_switch);
+ }
+
+ intel_cpufreq_trace(cpu, fast_switch ? INTEL_PSTATE_TRACE_FAST_SWITCH :
+ INTEL_PSTATE_TRACE_TARGET, old_pstate);
+
+ return target_pstate;
+}
+
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, old_pstate;
+ int target_pstate;
update_turbo_state();
freqs.new = target_freq;
cpufreq_freq_transition_begin(policy, &freqs);
+
switch (relation) {
case CPUFREQ_RELATION_L:
target_pstate = DIV_ROUND_UP(freqs.new, cpu->pstate.scaling);
target_pstate = DIV_ROUND_CLOSEST(freqs.new, cpu->pstate.scaling);
break;
}
- target_pstate = intel_pstate_prepare_request(cpu, target_pstate);
- old_pstate = cpu->pstate.current_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));
- }
+
+ target_pstate = intel_cpufreq_update_pstate(cpu, target_pstate, false);
+
freqs.new = target_pstate * cpu->pstate.scaling;
- intel_cpufreq_trace(cpu, INTEL_PSTATE_TRACE_TARGET, old_pstate);
+
cpufreq_freq_transition_end(policy, &freqs, false);
return 0;
unsigned int target_freq)
{
struct cpudata *cpu = all_cpu_data[policy->cpu];
- int target_pstate, old_pstate;
+ int target_pstate;
update_turbo_state();
target_pstate = DIV_ROUND_UP(target_freq, cpu->pstate.scaling);
- target_pstate = intel_pstate_prepare_request(cpu, target_pstate);
- old_pstate = cpu->pstate.current_pstate;
- intel_pstate_update_pstate(cpu, target_pstate);
- intel_cpufreq_trace(cpu, INTEL_PSTATE_TRACE_FAST_SWITCH, old_pstate);
+
+ target_pstate = intel_cpufreq_update_pstate(cpu, target_pstate, true);
+
return target_pstate * cpu->pstate.scaling;
}
return ret;
policy->cpuinfo.transition_latency = INTEL_CPUFREQ_TRANSITION_LATENCY;
- policy->transition_delay_us = INTEL_CPUFREQ_TRANSITION_DELAY;
/* This reflects the intel_pstate_get_cpu_pstates() setting. */
policy->cur = policy->cpuinfo.min_freq;
cpu = all_cpu_data[policy->cpu];
- if (hwp_active)
+ if (hwp_active) {
+ u64 value;
+
intel_pstate_get_hwp_max(policy->cpu, &turbo_max, &max_state);
- else
+ policy->transition_delay_us = INTEL_CPUFREQ_TRANSITION_DELAY_HWP;
+ rdmsrl_on_cpu(cpu->cpu, MSR_HWP_REQUEST, &value);
+ WRITE_ONCE(cpu->hwp_req_cached, value);
+ cpu->epp_cached = (value & GENMASK_ULL(31, 24)) >> 24;
+ } else {
turbo_max = cpu->pstate.turbo_pstate;
+ policy->transition_delay_us = INTEL_CPUFREQ_TRANSITION_DELAY;
+ }
min_freq = DIV_ROUND_UP(turbo_max * global.min_perf_pct, 100);
min_freq *= cpu->pstate.scaling;
}
}
put_online_cpus();
+
+ if (intel_pstate_driver == &intel_pstate)
+ intel_pstate_sysfs_hide_hwp_dynamic_boost();
+
intel_pstate_driver = NULL;
}
{
int ret;
+ if (driver == &intel_pstate)
+ intel_pstate_sysfs_expose_hwp_dynamic_boost();
+
memset(&global, 0, sizeof(global));
global.max_perf_pct = 100;
static int intel_pstate_unregister_driver(void)
{
- if (hwp_active)
- return -EBUSY;
-
cpufreq_unregister_driver(intel_pstate_driver);
intel_pstate_driver_cleanup();
hwp_active++;
hwp_mode_bdw = id->driver_data;
intel_pstate.attr = hwp_cpufreq_attrs;
- default_driver = &intel_pstate;
+ intel_cpufreq.attr = hwp_cpufreq_attrs;
+ if (!default_driver)
+ default_driver = &intel_pstate;
+
goto hwp_cpu_matched;
}
} else {
if (!str)
return -EINVAL;
- if (!strcmp(str, "disable")) {
+ if (!strcmp(str, "disable"))
no_load = 1;
- } else if (!strcmp(str, "active")) {
+ else if (!strcmp(str, "active"))
default_driver = &intel_pstate;
- } else if (!strcmp(str, "passive")) {
+ else if (!strcmp(str, "passive"))
default_driver = &intel_cpufreq;
- no_hwp = 1;
- }
+
if (!strcmp(str, "no_hwp")) {
pr_info("HWP disabled\n");
no_hwp = 1;
projects / platform / kernel / linux-rpi.git / commitdiff