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authorRafael J. Wysocki <rjw@sisk.pl>2011-12-21 15:59:45 -0500
committerRafael J. Wysocki <rjw@sisk.pl>2011-12-21 15:59:45 -0500
commitb00f4dc5ff022cb9cbaffd376d9454d7fa1e496f (patch)
tree40f1b232e2f1e8ac365317a14fdcbcb331722b46 /Documentation/power
parent1eac8111e0763853266a171ce11214da3a347a0a (diff)
parentb9e26dfdad5a4f9cbdaacafac6998614cc9c41bc (diff)
Merge branch 'master' into pm-sleep
* master: (848 commits) SELinux: Fix RCU deref check warning in sel_netport_insert() binary_sysctl(): fix memory leak mm/vmalloc.c: remove static declaration of va from __get_vm_area_node ipmi_watchdog: restore settings when BMC reset oom: fix integer overflow of points in oom_badness memcg: keep root group unchanged if creation fails nilfs2: potential integer overflow in nilfs_ioctl_clean_segments() nilfs2: unbreak compat ioctl cpusets: stall when updating mems_allowed for mempolicy or disjoint nodemask evm: prevent racing during tfm allocation evm: key must be set once during initialization mmc: vub300: fix type of firmware_rom_wait_states module parameter Revert "mmc: enable runtime PM by default" mmc: sdhci: remove "state" argument from sdhci_suspend_host x86, dumpstack: Fix code bytes breakage due to missing KERN_CONT IB/qib: Correct sense on freectxts increment and decrement RDMA/cma: Verify private data length cgroups: fix a css_set not found bug in cgroup_attach_proc oprofile: Fix uninitialized memory access when writing to writing to oprofilefs Revert "xen/pv-on-hvm kexec: add xs_reset_watches to shutdown watches from old kernel" ... Conflicts: kernel/cgroup_freezer.c
Diffstat (limited to 'Documentation/power')
-rw-r--r--Documentation/power/devices.txt111
-rw-r--r--Documentation/power/runtime_pm.txt40
2 files changed, 93 insertions, 58 deletions
diff --git a/Documentation/power/devices.txt b/Documentation/power/devices.txt
index 646a89e0c07d..3139fb505dce 100644
--- a/Documentation/power/devices.txt
+++ b/Documentation/power/devices.txt
@@ -123,9 +123,10 @@ please refer directly to the source code for more information about it.
123Subsystem-Level Methods 123Subsystem-Level Methods
124----------------------- 124-----------------------
125The core methods to suspend and resume devices reside in struct dev_pm_ops 125The core methods to suspend and resume devices reside in struct dev_pm_ops
126pointed to by the pm member of struct bus_type, struct device_type and 126pointed to by the ops member of struct dev_pm_domain, or by the pm member of
127struct class. They are mostly of interest to the people writing infrastructure 127struct bus_type, struct device_type and struct class. They are mostly of
128for buses, like PCI or USB, or device type and device class drivers. 128interest to the people writing infrastructure for platforms and buses, like PCI
129or USB, or device type and device class drivers.
129 130
130Bus drivers implement these methods as appropriate for the hardware and the 131Bus drivers implement these methods as appropriate for the hardware and the
131drivers using it; PCI works differently from USB, and so on. Not many people 132drivers using it; PCI works differently from USB, and so on. Not many people
@@ -139,41 +140,57 @@ sequencing in the driver model tree.
139 140
140/sys/devices/.../power/wakeup files 141/sys/devices/.../power/wakeup files
141----------------------------------- 142-----------------------------------
142All devices in the driver model have two flags to control handling of wakeup 143All device objects in the driver model contain fields that control the handling
143events (hardware signals that can force the device and/or system out of a low 144of system wakeup events (hardware signals that can force the system out of a
144power state). These flags are initialized by bus or device driver code using 145sleep state). These fields are initialized by bus or device driver code using
145device_set_wakeup_capable() and device_set_wakeup_enable(), defined in 146device_set_wakeup_capable() and device_set_wakeup_enable(), defined in
146include/linux/pm_wakeup.h. 147include/linux/pm_wakeup.h.
147 148
148The "can_wakeup" flag just records whether the device (and its driver) can 149The "power.can_wakeup" flag just records whether the device (and its driver) can
149physically support wakeup events. The device_set_wakeup_capable() routine 150physically support wakeup events. The device_set_wakeup_capable() routine
150affects this flag. The "should_wakeup" flag controls whether the device should 151affects this flag. The "power.wakeup" field is a pointer to an object of type
151try to use its wakeup mechanism. device_set_wakeup_enable() affects this flag; 152struct wakeup_source used for controlling whether or not the device should use
152for the most part drivers should not change its value. The initial value of 153its system wakeup mechanism and for notifying the PM core of system wakeup
153should_wakeup is supposed to be false for the majority of devices; the major 154events signaled by the device. This object is only present for wakeup-capable
154exceptions are power buttons, keyboards, and Ethernet adapters whose WoL 155devices (i.e. devices whose "can_wakeup" flags are set) and is created (or
155(wake-on-LAN) feature has been set up with ethtool. It should also default 156removed) by device_set_wakeup_capable().
156to true for devices that don't generate wakeup requests on their own but merely
157forward wakeup requests from one bus to another (like PCI bridges).
158 157
159Whether or not a device is capable of issuing wakeup events is a hardware 158Whether or not a device is capable of issuing wakeup events is a hardware
160matter, and the kernel is responsible for keeping track of it. By contrast, 159matter, and the kernel is responsible for keeping track of it. By contrast,
161whether or not a wakeup-capable device should issue wakeup events is a policy 160whether or not a wakeup-capable device should issue wakeup events is a policy
162decision, and it is managed by user space through a sysfs attribute: the 161decision, and it is managed by user space through a sysfs attribute: the
163power/wakeup file. User space can write the strings "enabled" or "disabled" to 162"power/wakeup" file. User space can write the strings "enabled" or "disabled"
164set or clear the "should_wakeup" flag, respectively. This file is only present 163to it to indicate whether or not, respectively, the device is supposed to signal
165for wakeup-capable devices (i.e. devices whose "can_wakeup" flags are set) 164system wakeup. This file is only present if the "power.wakeup" object exists
166and is created (or removed) by device_set_wakeup_capable(). Reads from the 165for the given device and is created (or removed) along with that object, by
167file will return the corresponding string. 166device_set_wakeup_capable(). Reads from the file will return the corresponding
168 167string.
169The device_may_wakeup() routine returns true only if both flags are set. 168
169The "power/wakeup" file is supposed to contain the "disabled" string initially
170for the majority of devices; the major exceptions are power buttons, keyboards,
171and Ethernet adapters whose WoL (wake-on-LAN) feature has been set up with
172ethtool. It should also default to "enabled" for devices that don't generate
173wakeup requests on their own but merely forward wakeup requests from one bus to
174another (like PCI Express ports).
175
176The device_may_wakeup() routine returns true only if the "power.wakeup" object
177exists and the corresponding "power/wakeup" file contains the string "enabled".
170This information is used by subsystems, like the PCI bus type code, to see 178This information is used by subsystems, like the PCI bus type code, to see
171whether or not to enable the devices' wakeup mechanisms. If device wakeup 179whether or not to enable the devices' wakeup mechanisms. If device wakeup
172mechanisms are enabled or disabled directly by drivers, they also should use 180mechanisms are enabled or disabled directly by drivers, they also should use
173device_may_wakeup() to decide what to do during a system sleep transition. 181device_may_wakeup() to decide what to do during a system sleep transition.
174However for runtime power management, wakeup events should be enabled whenever 182Device drivers, however, are not supposed to call device_set_wakeup_enable()
175the device and driver both support them, regardless of the should_wakeup flag. 183directly in any case.
176 184
185It ought to be noted that system wakeup is conceptually different from "remote
186wakeup" used by runtime power management, although it may be supported by the
187same physical mechanism. Remote wakeup is a feature allowing devices in
188low-power states to trigger specific interrupts to signal conditions in which
189they should be put into the full-power state. Those interrupts may or may not
190be used to signal system wakeup events, depending on the hardware design. On
191some systems it is impossible to trigger them from system sleep states. In any
192case, remote wakeup should always be enabled for runtime power management for
193all devices and drivers that support it.
177 194
178/sys/devices/.../power/control files 195/sys/devices/.../power/control files
179------------------------------------ 196------------------------------------
@@ -249,20 +266,31 @@ for every device before the next phase begins. Not all busses or classes
249support all these callbacks and not all drivers use all the callbacks. The 266support all these callbacks and not all drivers use all the callbacks. The
250various phases always run after tasks have been frozen and before they are 267various phases always run after tasks have been frozen and before they are
251unfrozen. Furthermore, the *_noirq phases run at a time when IRQ handlers have 268unfrozen. Furthermore, the *_noirq phases run at a time when IRQ handlers have
252been disabled (except for those marked with the IRQ_WAKEUP flag). 269been disabled (except for those marked with the IRQF_NO_SUSPEND flag).
253 270
254All phases use bus, type, or class callbacks (that is, methods defined in 271All phases use PM domain, bus, type, or class callbacks (that is, methods
255dev->bus->pm, dev->type->pm, or dev->class->pm). These callbacks are mutually 272defined in dev->pm_domain->ops, dev->bus->pm, dev->type->pm, or dev->class->pm).
256exclusive, so if the device type provides a struct dev_pm_ops object pointed to 273These callbacks are regarded by the PM core as mutually exclusive. Moreover,
257by its pm field (i.e. both dev->type and dev->type->pm are defined), the 274PM domain callbacks always take precedence over bus, type and class callbacks,
258callbacks included in that object (i.e. dev->type->pm) will be used. Otherwise, 275while type callbacks take precedence over bus and class callbacks, and class
259if the class provides a struct dev_pm_ops object pointed to by its pm field 276callbacks take precedence over bus callbacks. To be precise, the following
260(i.e. both dev->class and dev->class->pm are defined), the PM core will use the 277rules are used to determine which callback to execute in the given phase:
261callbacks from that object (i.e. dev->class->pm). Finally, if the pm fields of 278
262both the device type and class objects are NULL (or those objects do not exist), 279 1. If dev->pm_domain is present, the PM core will attempt to execute the
263the callbacks provided by the bus (that is, the callbacks from dev->bus->pm) 280 callback included in dev->pm_domain->ops. If that callback is not
264will be used (this allows device types to override callbacks provided by bus 281 present, no action will be carried out for the given device.
265types or classes if necessary). 282
283 2. Otherwise, if both dev->type and dev->type->pm are present, the callback
284 included in dev->type->pm will be executed.
285
286 3. Otherwise, if both dev->class and dev->class->pm are present, the
287 callback included in dev->class->pm will be executed.
288
289 4. Otherwise, if both dev->bus and dev->bus->pm are present, the callback
290 included in dev->bus->pm will be executed.
291
292This allows PM domains and device types to override callbacks provided by bus
293types or device classes if necessary.
266 294
267These callbacks may in turn invoke device- or driver-specific methods stored in 295These callbacks may in turn invoke device- or driver-specific methods stored in
268dev->driver->pm, but they don't have to. 296dev->driver->pm, but they don't have to.
@@ -283,9 +311,8 @@ When the system goes into the standby or memory sleep state, the phases are:
283 311
284 After the prepare callback method returns, no new children may be 312 After the prepare callback method returns, no new children may be
285 registered below the device. The method may also prepare the device or 313 registered below the device. The method may also prepare the device or
286 driver in some way for the upcoming system power transition (for 314 driver in some way for the upcoming system power transition, but it
287 example, by allocating additional memory required for this purpose), but 315 should not put the device into a low-power state.
288 it should not put the device into a low-power state.
289 316
290 2. The suspend methods should quiesce the device to stop it from performing 317 2. The suspend methods should quiesce the device to stop it from performing
291 I/O. They also may save the device registers and put it into the 318 I/O. They also may save the device registers and put it into the
diff --git a/Documentation/power/runtime_pm.txt b/Documentation/power/runtime_pm.txt
index 5336149f831b..c2ae8bf77d46 100644
--- a/Documentation/power/runtime_pm.txt
+++ b/Documentation/power/runtime_pm.txt
@@ -44,25 +44,33 @@ struct dev_pm_ops {
44}; 44};
45 45
46The ->runtime_suspend(), ->runtime_resume() and ->runtime_idle() callbacks 46The ->runtime_suspend(), ->runtime_resume() and ->runtime_idle() callbacks
47are executed by the PM core for either the power domain, or the device type 47are executed by the PM core for the device's subsystem that may be either of
48(if the device power domain's struct dev_pm_ops does not exist), or the class 48the following:
49(if the device power domain's and type's struct dev_pm_ops object does not 49
50exist), or the bus type (if the device power domain's, type's and class' 50 1. PM domain of the device, if the device's PM domain object, dev->pm_domain,
51struct dev_pm_ops objects do not exist) of the given device, so the priority 51 is present.
52order of callbacks from high to low is that power domain callbacks, device 52
53type callbacks, class callbacks and bus type callbacks, and the high priority 53 2. Device type of the device, if both dev->type and dev->type->pm are present.
54one will take precedence over low priority one. The bus type, device type and 54
55class callbacks are referred to as subsystem-level callbacks in what follows, 55 3. Device class of the device, if both dev->class and dev->class->pm are
56and generally speaking, the power domain callbacks are used for representing 56 present.
57power domains within a SoC. 57
58 4. Bus type of the device, if both dev->bus and dev->bus->pm are present.
59
60The PM core always checks which callback to use in the order given above, so the
61priority order of callbacks from high to low is: PM domain, device type, class
62and bus type. Moreover, the high-priority one will always take precedence over
63a low-priority one. The PM domain, bus type, device type and class callbacks
64are referred to as subsystem-level callbacks in what follows.
58 65
59By default, the callbacks are always invoked in process context with interrupts 66By default, the callbacks are always invoked in process context with interrupts
60enabled. However, subsystems can use the pm_runtime_irq_safe() helper function 67enabled. However, subsystems can use the pm_runtime_irq_safe() helper function
61to tell the PM core that a device's ->runtime_suspend() and ->runtime_resume() 68to tell the PM core that their ->runtime_suspend(), ->runtime_resume() and
62callbacks should be invoked in atomic context with interrupts disabled. 69->runtime_idle() callbacks may be invoked in atomic context with interrupts
63This implies that these callback routines must not block or sleep, but it also 70disabled for a given device. This implies that the callback routines in
64means that the synchronous helper functions listed at the end of Section 4 can 71question must not block or sleep, but it also means that the synchronous helper
65be used within an interrupt handler or in an atomic context. 72functions listed at the end of Section 4 may be used for that device within an
73interrupt handler or generally in an atomic context.
66 74
67The subsystem-level suspend callback is _entirely_ _responsible_ for handling 75The subsystem-level suspend callback is _entirely_ _responsible_ for handling
68the suspend of the device as appropriate, which may, but need not include 76the suspend of the device as appropriate, which may, but need not include