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Subject[PATCH v1 07/10] cpuidle: Allow idle states to be disabled by default
Date
From: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>

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: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
---

Changes from the RFC version:
- Call the new sysfs attribute "default_status" (instead of "initial_status").

---
Documentation/ABI/testing/sysfs-devices-system-cpu | 6 ++++++
Documentation/admin-guide/pm/cpuidle.rst | 3 +++
drivers/cpuidle/cpuidle.c | 6 +++++-
drivers/cpuidle/sysfs.c | 10 ++++++++++
include/linux/cpuidle.h | 1 +
5 files changed, 25 insertions(+), 1 deletion(-)

diff --git a/Documentation/ABI/testing/sysfs-devices-system-cpu b/Documentation/ABI/testing/sysfs-devices-system-cpu
index fc20cde63d1e..2e0e3b45d02a 100644
--- a/Documentation/ABI/testing/sysfs-devices-system-cpu
+++ b/Documentation/ABI/testing/sysfs-devices-system-cpu
@@ -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
diff --git a/Documentation/admin-guide/pm/cpuidle.rst b/Documentation/admin-guide/pm/cpuidle.rst
index e70b365dbc60..311cd7cc2b75 100644
--- a/Documentation/admin-guide/pm/cpuidle.rst
+++ b/Documentation/admin-guide/pm/cpuidle.rst
@@ -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.

diff --git a/drivers/cpuidle/cpuidle.c b/drivers/cpuidle/cpuidle.c
index 0005be5ea2b4..24eaa4c8138b 100644
--- a/drivers/cpuidle/cpuidle.c
+++ b/drivers/cpuidle/cpuidle.c
@@ -571,10 +571,14 @@ 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);

diff --git a/drivers/cpuidle/sysfs.c b/drivers/cpuidle/sysfs.c
index 38ef770be90d..254d1560dc19 100644
--- a/drivers/cpuidle/sysfs.c
+++ b/drivers/cpuidle/sysfs.c
@@ -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
};

diff --git a/include/linux/cpuidle.h b/include/linux/cpuidle.h
index 1dabe36bd011..ebfb52b3ffbf 100644
--- a/include/linux/cpuidle.h
+++ b/include/linux/cpuidle.h
@@ -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;
--
2.16.4




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