Commit 1a5d9dbb authored by Linus Torvalds's avatar Linus Torvalds
Browse files

Merge tag 'pm-5.9-rc1-3' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm

Pull one more power management update from Rafael Wysocki:
 "Modify the intel_pstate driver to allow it to work in the passive mode
  with hardware-managed P-states (HWP) enabled"

* tag 'pm-5.9-rc1-3' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm:
  cpufreq: intel_pstate: Implement passive mode with HWP enabled
parents 884e0d3d f3db6de5
......@@ -54,10 +54,13 @@ registered (see `below <status_attr_>`_).
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
-----------
......@@ -194,10 +197,11 @@ This is the default operation mode of ``intel_pstate`` for processors without
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".
......@@ -318,10 +322,9 @@ manuals need to be consulted to get to it too.
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``
......@@ -425,22 +428,16 @@ argument is passed to the kernel in the command line.
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
-----------------------------------
......@@ -484,8 +481,8 @@ Next, the following policy attributes have special meaning if
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
......@@ -526,11 +523,11 @@ on the following rules, regardless of the current operation mode of the driver:
3. The global and per-policy limits can be set independently.
If 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
In 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
......@@ -541,12 +538,11 @@ at all and the only way to set the limits is by using the policy attributes.
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
......@@ -650,12 +646,14 @@ of them have to be prepended with the ``intel_pstate=`` prefix.
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.
......@@ -670,13 +668,12 @@ of them have to be prepended with the ``intel_pstate=`` prefix.
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.
......
......@@ -73,8 +73,6 @@ static inline bool has_target(void)
static unsigned int __cpufreq_get(struct cpufreq_policy *policy);
static int cpufreq_init_governor(struct cpufreq_policy *policy);
static void cpufreq_exit_governor(struct cpufreq_policy *policy);
static int cpufreq_start_governor(struct cpufreq_policy *policy);
static void cpufreq_stop_governor(struct cpufreq_policy *policy);
static void cpufreq_governor_limits(struct cpufreq_policy *policy);
static int cpufreq_set_policy(struct cpufreq_policy *policy,
struct cpufreq_governor *new_gov,
......@@ -2266,7 +2264,7 @@ static void cpufreq_exit_governor(struct cpufreq_policy *policy)
module_put(policy->governor->owner);
}
static int cpufreq_start_governor(struct cpufreq_policy *policy)
int cpufreq_start_governor(struct cpufreq_policy *policy)
{
int ret;
......@@ -2293,7 +2291,7 @@ static int cpufreq_start_governor(struct cpufreq_policy *policy)
return 0;
}
static void cpufreq_stop_governor(struct cpufreq_policy *policy)
void cpufreq_stop_governor(struct cpufreq_policy *policy)
{
if (cpufreq_suspended || !policy->governor)
return;
......
......@@ -36,6 +36,7 @@
#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
......@@ -220,6 +221,7 @@ struct global_params {
* 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
......@@ -257,6 +259,7 @@ struct cpudata {
s16 epp_policy;
s16 epp_default;
s16 epp_saved;
s16 epp_cached;
u64 hwp_req_cached;
u64 hwp_cap_cached;
u64 last_io_update;
......@@ -639,6 +642,26 @@ static int intel_pstate_get_energy_pref_index(struct cpudata *cpu_data, int *raw
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)
......@@ -650,28 +673,12 @@ static int intel_pstate_set_energy_pref_index(struct cpudata *cpu_data,
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;
......@@ -697,10 +704,12 @@ static ssize_t show_energy_performance_available_preferences(
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;
......@@ -725,15 +734,44 @@ static ssize_t store_energy_performance_preference(
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(
......@@ -1145,8 +1183,6 @@ static ssize_t store_no_turbo(struct kobject *a, struct kobj_attribute *b,
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;
......@@ -1330,9 +1366,10 @@ static const struct attribute_group intel_pstate_attr_group = {
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",
......@@ -1357,17 +1394,31 @@ static void __init intel_pstate_sysfs_expose_params(void)
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)
......@@ -2247,7 +2298,10 @@ static int intel_pstate_verify_policy(struct cpufreq_policy_data *policy)
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)
......@@ -2255,12 +2309,10 @@ 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)
......@@ -2390,13 +2442,71 @@ static void intel_cpufreq_trace(struct cpudata *cpu, unsigned int trace_type, in
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();
......@@ -2404,6 +2514,7 @@ static int intel_cpufreq_target(struct cpufreq_policy *policy,
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);
......@@ -2415,15 +2526,11 @@ static int intel_cpufreq_target(struct cpufreq_policy *policy,
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;
......@@ -2433,15 +2540,14 @@ 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, 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;
}
......@@ -2461,7 +2567,6 @@ static int intel_cpufreq_cpu_init(struct cpufreq_policy *policy)
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;
......@@ -2473,10 +2578,18 @@ static int intel_cpufreq_cpu_init(struct cpufreq_policy *policy)
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;
......@@ -2553,6 +2666,10 @@ static void intel_pstate_driver_cleanup(void)
}
}
put_online_cpus();
if (intel_pstate_driver == &intel_pstate)
intel_pstate_sysfs_hide_hwp_dynamic_boost();
intel_pstate_driver = NULL;
}
......@@ -2560,6 +2677,9 @@ static int intel_pstate_register_driver(struct cpufreq_driver *driver)
{
int ret;
if (driver == &intel_pstate)
intel_pstate_sysfs_expose_hwp_dynamic_boost();
memset(&global, 0, sizeof(global));
global.max_perf_pct = 100;
......@@ -2577,9 +2697,6 @@ static int intel_pstate_register_driver(struct cpufreq_driver *driver)
static int intel_pstate_unregister_driver(void)
{
if (hwp_active)
return -EBUSY;
cpufreq_unregister_driver(intel_pstate_driver);
intel_pstate_driver_cleanup();
......@@ -2835,7 +2952,10 @@ static int __init intel_pstate_init(void)
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 {
......@@ -2906,14 +3026,13 @@ 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, "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;