Commit 75a80267 authored by Rafael J. Wysocki's avatar Rafael J. Wysocki
Browse files

cpuidle: Allow idle states to be disabled by default 



In certain situations it may be useful to prevent some idle states
from being used by default while allowing user space to enable them
later on.

For this purpose, introduce a new state flag, CPUIDLE_FLAG_OFF, to
mark idle states that should be disabled by default, make the core
set CPUIDLE_STATE_DISABLED_BY_USER for those states at the
initialization time and add a new state attribute in sysfs,
"default_status", to inform user space of the initial status of
the given idle state ("disabled" if CPUIDLE_FLAG_OFF is set for it,
"enabled" otherwise).

Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
parent 18734958

Documentation/ABI/testing/sysfs-devices-system-cpu

+6 −0
Original line number Diff line number Diff line
@@ -196,6 +196,12 @@ Description: 
		does not reflect it. Likewise, if one enables a deep state but a

		lighter state still is disabled, then this has no effect.



What:		/sys/devices/system/cpu/cpuX/cpuidle/stateN/default_status

Date:		December 2019

KernelVersion:	v5.6

Contact:	Linux power management list <linux-pm@vger.kernel.org>

Description:

		(RO) The default status of this state, "enabled" or "disabled".



What:		/sys/devices/system/cpu/cpuX/cpuidle/stateN/residency

Date:		March 2014

Documentation/admin-guide/pm/cpuidle.rst

+3 −0
Original line number Diff line number Diff line
@@ -506,6 +506,9 @@ object corresponding to it, as follows: 
``disable``

	Whether or not this idle state is disabled.



``default_status``

	The default status of this state, "enabled" or "disabled".



``latency``

	Exit latency of the idle state in microseconds.

drivers/cpuidle/cpuidle.c

+5 −1
Original line number Diff line number Diff line
@@ -572,10 +572,14 @@ static int __cpuidle_register_device(struct cpuidle_device *dev) 
	if (!try_module_get(drv->owner))

		return -EINVAL;



	for (i = 0; i < drv->state_count; i++)

	for (i = 0; i < drv->state_count; i++) {

		if (drv->states[i].flags & CPUIDLE_FLAG_UNUSABLE)

			dev->states_usage[i].disable |= CPUIDLE_STATE_DISABLED_BY_DRIVER;



		if (drv->states[i].flags & CPUIDLE_FLAG_OFF)

			dev->states_usage[i].disable |= CPUIDLE_STATE_DISABLED_BY_USER;

	}



	per_cpu(cpuidle_devices, dev->cpu) = dev;

	list_add(&dev->device_list, &cpuidle_detected_devices);

drivers/cpuidle/sysfs.c

+10 −0
Original line number Diff line number Diff line
@@ -327,6 +327,14 @@ static ssize_t store_state_disable(struct cpuidle_state *state, 
	return size;

}



static ssize_t show_state_default_status(struct cpuidle_state *state,

					  struct cpuidle_state_usage *state_usage,

					  char *buf)

{

	return sprintf(buf, "%s\n",

		       state->flags & CPUIDLE_FLAG_OFF ? "disabled" : "enabled");

}



define_one_state_ro(name, show_state_name);

define_one_state_ro(desc, show_state_desc);

define_one_state_ro(latency, show_state_exit_latency);
@@ -337,6 +345,7 @@ define_one_state_ro(time, show_state_time); 
define_one_state_rw(disable, show_state_disable, store_state_disable);

define_one_state_ro(above, show_state_above);

define_one_state_ro(below, show_state_below);

define_one_state_ro(default_status, show_state_default_status);



static struct attribute *cpuidle_state_default_attrs[] = {

	&attr_name.attr,
@@ -349,6 +358,7 @@ static struct attribute *cpuidle_state_default_attrs[] = { 
	&attr_disable.attr,

	&attr_above.attr,

	&attr_below.attr,

	&attr_default_status.attr,

	NULL

};

include/linux/cpuidle.h

+1 −0
Original line number Diff line number Diff line
@@ -77,6 +77,7 @@ struct cpuidle_state { 
#define CPUIDLE_FLAG_COUPLED	BIT(1) /* state applies to multiple cpus */

#define CPUIDLE_FLAG_TIMER_STOP BIT(2) /* timer is stopped on this state */

#define CPUIDLE_FLAG_UNUSABLE	BIT(3) /* avoid using this state */

#define CPUIDLE_FLAG_OFF	BIT(4) /* disable this state by default */



struct cpuidle_device_kobj;

struct cpuidle_state_kobj;

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