From 87d1b3e60b55ef65f10054ccc319e5d67cf010e9 Mon Sep 17 00:00:00 2001 From: "Rafael J. Wysocki" Date: Sat, 6 Mar 2010 21:28:17 +0100 Subject: PM / Runtime: Document power.runtime_auto and related functions The power.runtime_auto device flag and the helper functions pm_runtime_allow() and pm_runtime_forbid() used to modify it are a part of the run-time power management framework and therefore they should be described in Documentation/power/runtime_pm.txt. Signed-off-by: Rafael J. Wysocki --- Documentation/power/runtime_pm.txt | 28 ++++++++++++++++++++++++++++ 1 file changed, 28 insertions(+) (limited to 'Documentation') diff --git a/Documentation/power/runtime_pm.txt b/Documentation/power/runtime_pm.txt index 356fd86f4ea..f1937064168 100644 --- a/Documentation/power/runtime_pm.txt +++ b/Documentation/power/runtime_pm.txt @@ -224,6 +224,12 @@ defined in include/linux/pm.h: RPM_SUSPENDED, which means that each device is initially regarded by the PM core as 'suspended', regardless of its real hardware status + unsigned int runtime_auto; + - if set, indicates that the user space has allowed the device driver to + power manage the device at run time via the /sys/devices/.../power/control + interface; it may only be modified with the help of the pm_runtime_allow() + and pm_runtime_forbid() helper functions + All of the above fields are members of the 'power' member of 'struct device'. 4. Run-time PM Device Helper Functions @@ -329,6 +335,16 @@ drivers/base/power/runtime.c and include/linux/pm_runtime.h: 'power.runtime_error' is set or 'power.disable_depth' is greater than zero) + void pm_runtime_allow(struct device *dev); + - set the power.runtime_auto flag for the device and decrease its usage + counter (used by the /sys/devices/.../power/control interface to + effectively allow the device to be power managed at run time) + + void pm_runtime_forbid(struct device *dev); + - unset the power.runtime_auto flag for the device and increase its usage + counter (used by the /sys/devices/.../power/control interface to + effectively prevent the device from being power managed at run time) + It is safe to execute the following helper functions from interrupt context: pm_request_idle() @@ -382,6 +398,18 @@ may be desirable to suspend the device as soon as ->probe() or ->remove() has finished, so the PM core uses pm_runtime_idle_sync() to invoke the subsystem-level idle callback for the device at that time. +The user space can effectively disallow the driver of the device to power manage +it at run time by changing the value of its /sys/devices/.../power/control +attribute to "on", which causes pm_runtime_forbid() to be called. In principle, +this mechanism may also be used by the driver to effectively turn off the +run-time power management of the device until the user space turns it on. +Namely, during the initialization the driver can make sure that the run-time PM +status of the device is 'active' and call pm_runtime_forbid(). It should be +noted, however, that if the user space has already intentionally changed the +value of /sys/devices/.../power/control to "auto" to allow the driver to power +manage the device at run time, the driver may confuse it by using +pm_runtime_forbid() this way. + 6. Run-time PM and System Sleep Run-time PM and system sleep (i.e., system suspend and hibernation, also known -- cgit v1.2.3 From d690b2cd222afc75320b9b8e9da7df02e9e630ca Mon Sep 17 00:00:00 2001 From: "Rafael J. Wysocki" Date: Sat, 6 Mar 2010 21:28:37 +0100 Subject: PM: Provide generic subsystem-level callbacks There are subsystems whose power management callbacks only need to invoke the callbacks provided by device drivers. Still, their system sleep PM callbacks should play well with the runtime PM callbacks, so that devices suspended at run time can be left in that state for a system sleep transition. Provide a set of generic PM callbacks for such subsystems and define convenience macros for populating dev_pm_ops structures. Signed-off-by: Rafael J. Wysocki --- Documentation/power/runtime_pm.txt | 65 ++++++++++++++++++++++++++++++++++++++ 1 file changed, 65 insertions(+) (limited to 'Documentation') diff --git a/Documentation/power/runtime_pm.txt b/Documentation/power/runtime_pm.txt index f1937064168..ab00eeddeca 100644 --- a/Documentation/power/runtime_pm.txt +++ b/Documentation/power/runtime_pm.txt @@ -335,6 +335,10 @@ drivers/base/power/runtime.c and include/linux/pm_runtime.h: 'power.runtime_error' is set or 'power.disable_depth' is greater than zero) + bool pm_runtime_suspended(struct device *dev); + - return true if the device's runtime PM status is 'suspended', or false + otherwise + void pm_runtime_allow(struct device *dev); - set the power.runtime_auto flag for the device and decrease its usage counter (used by the /sys/devices/.../power/control interface to @@ -459,3 +463,64 @@ The PM core always increments the run-time usage counter before calling the ->prepare() callback and decrements it after calling the ->complete() callback. Hence disabling run-time PM temporarily like this will not cause any run-time suspend callbacks to be lost. + +7. Generic subsystem callbacks + +Subsystems may wish to conserve code space by using the set of generic power +management callbacks provided by the PM core, defined in +driver/base/power/generic_ops.c: + + int pm_generic_runtime_idle(struct device *dev); + - invoke the ->runtime_idle() callback provided by the driver of this + device, if defined, and call pm_runtime_suspend() for this device if the + return value is 0 or the callback is not defined + + int pm_generic_runtime_suspend(struct device *dev); + - invoke the ->runtime_suspend() callback provided by the driver of this + device and return its result, or return -EINVAL if not defined + + int pm_generic_runtime_resume(struct device *dev); + - invoke the ->runtime_resume() callback provided by the driver of this + device and return its result, or return -EINVAL if not defined + + int pm_generic_suspend(struct device *dev); + - if the device has not been suspended at run time, invoke the ->suspend() + callback provided by its driver and return its result, or return 0 if not + defined + + int pm_generic_resume(struct device *dev); + - invoke the ->resume() callback provided by the driver of this device and, + if successful, change the device's runtime PM status to 'active' + + int pm_generic_freeze(struct device *dev); + - if the device has not been suspended at run time, invoke the ->freeze() + callback provided by its driver and return its result, or return 0 if not + defined + + int pm_generic_thaw(struct device *dev); + - if the device has not been suspended at run time, invoke the ->thaw() + callback provided by its driver and return its result, or return 0 if not + defined + + int pm_generic_poweroff(struct device *dev); + - if the device has not been suspended at run time, invoke the ->poweroff() + callback provided by its driver and return its result, or return 0 if not + defined + + int pm_generic_restore(struct device *dev); + - invoke the ->restore() callback provided by the driver of this device and, + if successful, change the device's runtime PM status to 'active' + +These functions can be assigned to the ->runtime_idle(), ->runtime_suspend(), +->runtime_resume(), ->suspend(), ->resume(), ->freeze(), ->thaw(), ->poweroff(), +or ->restore() callback pointers in the subsystem-level dev_pm_ops structures. + +If a subsystem wishes to use all of them at the same time, it can simply assign +the GENERIC_SUBSYS_PM_OPS macro, defined in include/linux/pm.h, to its +dev_pm_ops structure pointer. + +Device drivers that wish to use the same function as a system suspend, freeze, +poweroff and run-time suspend callback, and similarly for system resume, thaw, +restore, and run-time resume, can achieve this with the help of the +UNIVERSAL_DEV_PM_OPS macro defined in include/linux/pm.h (possibly setting its +last argument to NULL). -- cgit v1.2.3