The removal of a device from a PM domain doesn't have to browse
the domain's device list, because it can check directly if the
device belongs to the given domain.  Moreover, it should clear
the domain_data pointer in dev->power.subsys_data, because
dev_pm_put_subsys_data(dev) may not remove dev->power.subsys_data
and the stale domain data pointer may cause problems to happen.

Rework pm_genpd_remove_device() taking the above observations into
account.
Signed-off-by: NRafael J. Wysocki <rjw@sisk.pl>

After the previous changes in default_stop_ok() and
default_power_down_ok() for PM domains, there are two fields in
struct dev_pm_info that aren't necessary any more,  suspend_time
and max_time_suspended_ns.

Remove those fields along with all of the code that accesses them,
which simplifies the runtime PM framework quite a bit.
Signed-off-by: NRafael J. Wysocki <rjw@sisk.pl>

The existing default domain power down governor function for PM
domains, default_power_down_ok(), is supposed to check whether or not
the PM QoS latency constraints of the devices in the domain will be
violated if the domain is turned off by pm_genpd_poweroff().
However, the computations carried out by it don't reflect the
definition of the PM QoS latency constrait in
Documentation/ABI/testing/sysfs-devices-power.

Make default_power_down_ok() follow the definition of the PM QoS
latency constrait.  In particular, make it only take latencies into
account, because it doesn't matter how much time has elapsed since
the domain's devices were suspended for the computation.

Remove the break_even_ns and power_off_time fields from
struct generic_pm_domain, because they are not necessary any more.
Signed-off-by: NRafael J. Wysocki <rjw@sisk.pl>

The existing default device stop governor function for PM domains,
default_stop_ok(), is supposed to check whether or not the device's
PM QoS latency constraint will be violated if the device is stopped
by pm_genpd_runtime_suspend().  However, the computations carried out
by it don't reflect the definition of the PM QoS latency constrait in
Documentation/ABI/testing/sysfs-devices-power.

Make default_stop_ok() follow the definition of the PM QoS latency
constrait.  In particular, make it take the device's start and stop
latencies correctly.

Add a new field, effective_constraint_ns, to struct gpd_timing_data
and use it to store the difference between the device's PM QoS
constraint and its resume latency for use by the device's parent
(the effective_constraint_ns values for the children are used for
computing the parent's one along with its PM QoS constraint).

Remove the break_even_ns field from struct gpd_timing_data, because
it's not used any more.
Signed-off-by: NRafael J. Wysocki <rjw@sisk.pl>

Power domains that were off before hibernation shouldn't be turned on
during device restore, so prevent that from happening.

This change fixes up commit 65533bbf

    PM / Domains: Fix hibernation restore of devices, v2

that didn't include it by mistake.
Signed-off-by: NRafael J. Wysocki <rjw@sisk.pl>

The TMU device on the Mackerel board belongs to the A4R power domain
and loses power when the domain is turned off.  Unfortunately, the
TMU driver is not prepared to cope with such situations and crashes
the system when that happens.  To work around this problem introduce
a new helper function, pm_genpd_dev_always_on(), allowing a device
driver to mark its device as "always on" in case it belongs to a PM
domain, which will make the generic PM domains core code avoid
powering off the domain containing the device, both at run time and
during system suspend.
Signed-off-by: NRafael J. Wysocki <rjw@sisk.pl>
Tested-by: NSimon Horman <horms@verge.net.au>
Acked-by: NPaul Mundt <lethal@linux-sh.org>
Cc: stable@vger.kernel.org

During resume from hibernation pm_genpd_restore_noirq() should only
power off domains whose suspend_power_off flags are set once and
not every time it is called for a device in the given domain.
Moreover, it shouldn't decrement genpd->suspended_count, because
that field is not touched during device freezing and therefore it is
always equal to 0 when pm_genpd_restore_noirq() runs for the first
device in the given domain.

This means pm_genpd_restore_noirq() may use genpd->suspended_count
to determine whether or not it it has been called for the domain in
question already in this cycle (it only needs to increment that
field every time it runs for this purpose) and whether or not it
should check if the domain needs to be powered off.  For that to
work, though, pm_genpd_prepare() has to clear genpd->suspended_count
when it runs for the first device in the given domain (in which case
that flag need not be cleared during domain initialization).
Signed-off-by: NRafael J. Wysocki <rjw@sisk.pl>
Cc: stable@vger.kernel.org

During system suspend pm_genpd_suspend_noirq() checks if the given
device is in a wakeup path (i.e. it appears to be needed for one or
more wakeup devices to work or is a wakeup device itself) and if it
needs to be "active" for wakeup to work.  If that is the case, the
function returns 0 without incrementing the device domain's counter
of suspended devices and without executing genpd_stop_dev() for the
device.  In consequence, the device is not stopped (e.g. its clock
isn't disabled) and power is always supplied to its domain in the
resulting system sleep state.

However, pm_genpd_resume_noirq() doesn't repeat that check and it
runs genpd_start_dev() and decrements the domain's counter of
suspended devices even for the wakeup device that weren't stopped by
pm_genpd_suspend_noirq().  As a result, the start callback may be run
unnecessarily for them and their domains' counters of suspended
devices may become negative.  Both outcomes aren't desirable, so fix
pm_genpd_resume_noirq() to look for wakeup devices that might not be
stopped by during system suspend.
Signed-off-by: NRafael J. Wysocki <rjw@sisk.pl>
Tested-by: NSimon Horman <horms@verge.net.au>
Cc: stable@vger.kernel.org

After the introduction of the late/early phases of device
suspend/resume during system-wide power transitions it is possible
to make the generic PM domains code execute its default late/early
device suspend/resume callbacks during those phases instead of the
corresponding _noirq phases.  The _noirq device suspend/resume
phases were only used for executing those callbacks, because this
was the only way it could be done, but now we can do better.
Signed-off-by: NRafael J. Wysocki <rjw@sisk.pl>

A device node pointer is added to generic pm domain structure to associate
the domain with a node in the device tree. The platform code parses the
device tree to find available nodes representing the generic power domain,
instantiates the available domains and initializes them by calling
pm_genpd_init().

Nodes representing the devices include a phandle of the power domain to
which it belongs. As these devices get instantiated, the driver code
checkes for availability of a power domain phandle, converts the phandle
to a device node and uses the new pm_genpd_of_add_device() api to
associate the device with a power domain.

pm_genpd_of_add_device() runs through its list of registered power domains
and matches the OF node of the domain with the one specified as the
parameter. If a match is found, the device is associated with the matched
domain.

Cc: Rob Herring <rob.herring@calxeda.com>
Cc: Grant Likely <grant.likely@secretlab.ca>
Signed-off-by: NThomas Abraham <thomas.abraham@linaro.org>
Acked-by: NRafael J. Wysocki <rjw@sisk.pl>
Signed-off-by: NKukjin Kim <kgene.kim@samsung.com>

Some callback functions defined in drivers/base/power/domain.c are
only necessary if CONFIG_PM_SLEEP is set and they call some other
functions that are only available in that case.  For this reason,
they should not be compiled at all when CONFIG_PM_SLEEP is not set.
Reported-by: NMagnus Damm <damm@opensource.se>
Signed-off-by: NRafael J. Wysocki <rjw@sisk.pl>

Commit d23b9b00 (PM / Domains: Rework
system suspend callback routines (v2)) broke the system suspend and
resume handling by devices belonging to generic PM domains, because
it used freeze/thaw callbacks instead of suspend/resume ones and
didn't initialize device callbacks for system suspend/resume
properly at all.  Fix those problems.
Signed-off-by: NRafael J. Wysocki <rjw@sisk.pl>

Add a name member pointer to struct generic_pm_domain and use it in
diagnostic messages regarding the domain power-off and power-on
latencies.  Update the ARM shmobile SH7372 code to assign names to
the PM domains used by it.
Signed-off-by: NRafael J. Wysocki <rjw@sisk.pl>
Acked-by: NMagnus Damm <damm@opensource.se>

Measure the time of execution of the .stop(), .start(), .save_state()
and .restore_state() PM domain device callbacks and if the result
is greater than the corresponding latency value stored in the
device's struct generic_pm_domain_data object, replace the inaccurate
value with the measured time.

Do analogously for the PM domains' .power_off() and .power_off()
callbacks.
Signed-off-by: NRafael J. Wysocki <rjw@sisk.pl>

Add a function deciding whether or not a given PM domain should
be powered off on the basis of the PM QoS constraints of devices
belonging to it and their PM QoS timing data.
Signed-off-by: NRafael J. Wysocki <rjw@sisk.pl>

Add a function deciding whether or not devices should be stopped in
pm_genpd_runtime_suspend() depending on their PM QoS constraints
and stop/start timing values.  Make it possible to add information
used by this function to device objects.
Signed-off-by: NRafael J. Wysocki <rjw@sisk.pl>
Acked-by: NMagnus Damm <damm@opensource.se>

The current generic PM domains code attempts to use the generic
system suspend operations along with the domains' device stop/start
routines, which requires device drivers to assume that their
system suspend/resume (and hibernation/restore) callbacks will always
be used with generic PM domains.  However, in theory, the same
hardware may be used in devices that don't belong to any PM domain,
in which case it would be necessary to add "fake" PM domains to
satisfy the above assumption.  Also, the domain the hardware belongs
to may not be handled with the help of the generic code.

To allow device drivers that may be used along with the generic PM
domains code of more flexibility, add new device callbacks,
.suspend(), .suspend_late(), .resume_early(), .resume(), .freeze(),
.freeze_late(), .thaw_early(), and .thaw(), that can be supplied by
the drivers in addition to their "standard" system suspend and
hibernation callbacks.  These new callbacks, if defined, will be used
by the generic PM domains code for the handling of system suspend and
hibernation instead of the "standard" ones.  This will allow drivers
to be designed to work with generic PM domains as well as without
them.

For backwards compatibility, introduce default implementations of the
new callbacks for PM domains that will execute pm_generic_suspend(),
pm_generic_suspend_noirq(), pm_generic_resume_noirq(),
pm_generic_resume(), pm_generic_freeze(), pm_generic_freeze_noirq(),
pm_generic_thaw_noirq(), and pm_generic_thaw(), respectively, for the
given device if its driver doesn't define those callbacks.
Signed-off-by: NRafael J. Wysocki <rjw@sisk.pl>

The current PM domains code uses device drivers' .runtime_suspend()
and .runtime_resume() callbacks as the "save device state" and
"restore device state" operations, which may not be appropriate in
general, because it forces drivers to assume that they always will
be used with generic PM domains.  However, in theory, the same
hardware may be used in devices that don't belong to any PM
domain, in which case it would be necessary to add "fake" PM
domains to satisfy the above assumption.  It also may be located in
a PM domain that's not handled with the help of the generic code.

To allow device drivers that may be used along with the generic PM
domains code of more flexibility, introduce new device callbacks,
.save_state() and .restore_state(), that can be supplied by the
drivers in addition to their "standard" runtime PM callbacks.  This
will allow the drivers to be designed to work with generic PM domains
as well as without them.

For backwards compatibility, introduce default .save_state() and
.restore_state() callback routines for PM domains that will execute
a device driver's .runtime_suspend() and .runtime_resume() callbacks,
respectively, for the given device if the driver doesn't provide its
own implementations of .save_state() and .restore_state().
Signed-off-by: NRafael J. Wysocki <rjw@sisk.pl>

The current generic PM domains code requires that the same .stop(),
.start() and .active_wakeup() device callback routines be used for
all devices in the given domain, which is inflexible and may not
cover some specific use cases.  For this reason, make it possible to
use device specific .start()/.stop() and .active_wakeup() callback
routines by adding corresponding callback pointers to struct
generic_pm_domain_data.  Add a new helper routine,
pm_genpd_register_callbacks(), that can be used to populate
the new per-device callback pointers.

Modify the shmobile's power domains code to allow drivers to add
their own code to be run during the device stop and start operations
with the help of the new callback pointers.
Signed-off-by: NRafael J. Wysocki <rjw@sisk.pl>
Acked-by: NMagnus Damm <damm@opensource.se>

The generic PM domains code in drivers/base/power/domain.c has
to avoid powering off domains that provide power to wakeup devices
during system suspend.  Currently, however, this only works for
wakeup devices directly belonging to the given domain and not for
their children (or the children of their children and so on).
Thus, if there's a wakeup device whose parent belongs to a power
domain handled by the generic PM domains code, the domain will be
powered off during system suspend preventing the device from
signaling wakeup.

To address this problem introduce a device flag, power.wakeup_path,
that will be set during system suspend for all wakeup devices,
their parents, the parents of their parents and so on.  This way,
all wakeup paths in the device hierarchy will be marked and the
generic PM domains code will only need to avoid powering off
domains containing devices whose power.wakeup_path is set.
Signed-off-by: NRafael J. Wysocki <rjw@sisk.pl>

The struct pm_domain_data data type is defined in such a way that
adding new fields specific to the generic PM domains code will
require include/linux/pm.h to be modified.  As a result, data types
used only by the generic PM domains code will be defined in two
headers, although they all should be defined in pm_domain.h and
pm.h will need to include more headers, which won't be very nice.

For this reason change the definition of struct pm_subsys_data
so that its domain_data member is a pointer, which will allow
struct pm_domain_data to be subclassed by various PM domains
implementations.  Remove the need_restore member from
struct pm_domain_data and make the generic PM domains code
subclass it by adding the need_restore member to the new data type.
Signed-off-by: NRafael J. Wysocki <rjw@sisk.pl>

The generic PM domains framework currently doesn't work with devices
whose power.irq_safe flag is set, because runtime PM callbacks for
such devices are run with interrupts disabled and the callbacks
provided by the generic PM domains framework use domain mutexes
and may sleep.  However, such devices very well may belong to
power domains on some systems, so the generic PM domains framework
should take them into account.

For this reason, modify the generic PM domains framework so that the
domain .power_off() and .power_on() callbacks are never executed for
a domain containing devices with power.irq_safe set, although the
.stop_device() and .start_device() callbacks are still run for them.

Additionally, introduce a flag allowing the creator of a
struct generic_pm_domain object to indicate that its .stop_device()
and .start_device() callbacks may be run in interrupt context
(might_sleep_if() triggers if that flag is not set and one of those
callbacks is run in interrupt context).
Signed-off-by: NRafael J. Wysocki <rjw@sisk.pl>

Currently pm_genpd_runtime_resume() has to walk the list of devices
from the device's PM domain to find the corresponding device list
object containing the need_restore field to check if the driver's
.runtime_resume() callback should be executed for the device.
This is suboptimal and can be simplified by using power.sybsys_data
to store device information used by the generic PM domains code.
Signed-off-by: NRafael J. Wysocki <rjw@sisk.pl>

Change the name of the second argument of pm_genpd_add_subdomain()
so that it is (a) shorter and (b) in agreement with the name of
the second argument of pm_genpd_add_subdomain().
Signed-off-by: NRafael J. Wysocki <rjw@sisk.pl>

Since it is now possible for a PM domain to have multiple masters
instead of one parent, rename the "wait for parent" status to reflect
the new situation.
Signed-off-by: NRafael J. Wysocki <rjw@sisk.pl>

Currently, for a given generic PM domain there may be only one parent
domain (i.e. a PM domain it depends on).  However, there is at least
one real-life case in which there should be two parents (masters) for
one PM domain (the A3RV domain on SH7372 turns out to depend on the
A4LC domain and it depends on the A4R domain and the same time). For
this reason, allow a PM domain to have multiple parents (masters) by
introducing objects representing links between PM domains.

The (logical) links between PM domains represent relationships in
which one domain is a master (i.e. it is depended on) and another
domain is a slave (i.e. it depends on the master) with the rule that
the slave cannot be powered on if the master is not powered on and
the master cannot be powered off if the slave is not powered off.
Each struct generic_pm_domain object representing a PM domain has
two lists of links, a list of links in which it is a master and
a list of links in which it is a slave.  The first of these lists
replaces the list of subdomains and the second one is used in place
of the parent pointer.

Each link is represented by struct gpd_link object containing
pointers to the master and the slave and two struct list_head
members allowing it to hook into two lists (the master's list
of "master" links and the slave's list of "slave" links).  This
allows the code to get to the link from each side (either from
the master or from the slave) and follow it in each direction.
Signed-off-by: NRafael J. Wysocki <rjw@sisk.pl>

The next patch will make it possible for a generic PM domain to have
multiple parents (i.e. multiple PM domains it depends on).  To
prepare for that change it is necessary to change pm_genpd_poweron()
so that it doesn't jump to the start label after running itself
recursively for the parent domain.  For this purpose, introduce a new
PM domain status value GPD_STATE_WAIT_PARENT that will be set by
pm_genpd_poweron() before calling itself recursively for the parent
domain and modify the code in drivers/base/power/domain.c so that
the GPD_STATE_WAIT_PARENT status is guaranteed to be preserved during
the execution of pm_genpd_poweron() for the parent.

This change also causes pm_genpd_add_subdomain() and
pm_genpd_remove_subdomain() to wait for started pm_genpd_poweron() to
complete and allows pm_genpd_runtime_resume() to avoid dropping the
lock after powering on the PM domain.
Signed-off-by: NRafael J. Wysocki <rjw@sisk.pl>

If pm_genpd_remove_subdomain() is called to remove a PM domain's
subdomain and pm_genpd_poweron() is called for that subdomain at
the same time, and the pm_genpd_poweron() called by it recursively
for the parent returns an error, the first pm_genpd_poweron()'s
error code path will attempt to decrement the subdomain counter of
a PM domain that it's not a subdomain of any more.

Rearrange the code in pm_genpd_poweron() to prevent this from
happening.
Signed-off-by: NRafael J. Wysocki <rjw@sisk.pl>

After the subdomain counter in struct generic_pm_domain has been
changed into an atomic_t field, it is possible to modify
pm_genpd_poweron() and pm_genpd_poweroff() so that they don't take
the parents locks.  This requires pm_genpd_poweron() to increment
the parent's subdomain counter before calling itself recursively
for the parent and to decrement it if an error is to be returned.
Signed-off-by: NRafael J. Wysocki <rjw@sisk.pl>

Currently, pm_genpd_poweron() and pm_genpd_poweroff() need to take
the parent PM domain's lock in order to modify the parent's counter
of active subdomains in a nonracy way.  This causes the locking to be
considerably complex and in fact is not necessary, because the
subdomain counters may be implemented as atomic fields and they
won't have to be modified under a lock.

Replace the unsigned in sd_count field in struct generic_pm_domain
by an atomic_t one and modify the code in drivers/base/power/domain.c
to take this change into account.

This patch doesn't change the locking yet, that is going to be done
in a separate subsequent patch.
Signed-off-by: NRafael J. Wysocki <rjw@sisk.pl>

Function genpd_queue_power_off_work() is not defined for
CONFIG_PM_RUNTIME, so pm_genpd_poweroff_unused() causes a build
error to happen in that case.  Fix the problem by making
pm_genpd_poweroff_unused() depend on CONFIG_PM_RUNTIME too.
Signed-off-by: NRafael J. Wysocki <rjw@sisk.pl>

The local variable ret is defined twice in pm_genpd_poweron(), which
causes this function to always return 0, even if the PM domain's
.power_on() callback fails, in which case an error code should be
returned.

Remove the wrong second definition of ret and additionally remove an
unnecessary definition of wait from pm_genpd_poweron().
Signed-off-by: NRafael J. Wysocki <rjw@sisk.pl>

Currently pm_genpd_poweroff() discards error codes returned by
the PM domain's .power_off() callback, because it's safer to always
regard the domain as inaccessible to drivers after a failing
.power_off().  Still, there are situations in which the low-level
code may want to indicate that it doesn't want to power off the
domain, so allow it to do that by returning -EBUSY from .power_off().
Signed-off-by: NRafael J. Wysocki <rjw@sisk.pl>
Acked-by: NMagnus Damm <damm@opensource.se>

Make pd_power_down_a3rv() use genpd_queue_power_off_work() to queue
up the powering off of the A4LC domain to avoid queuing it up when
it is pending.
Signed-off-by: NRafael J. Wysocki <rjw@sisk.pl>
Acked-by: NMagnus Damm <damm@opensource.se>

Add a new function pm_genpd_poweroff_unused() queuing up the
execution of pm_genpd_poweroff() for every initialized generic PM
domain.  Calling it will cause every generic PM domain without
devices in use to be powered off.
Signed-off-by: NRafael J. Wysocki <rjw@sisk.pl>
Acked-by: NMagnus Damm <damm@opensource.se>

In theory it is possible that pm_genpd_poweroff() for two different
subdomains of the same parent domain will attempt to queue up the
execution of pm_genpd_poweroff() for the parent twice in a row.  This
would lead to unpleasant consequences, so prevent it from happening
by checking if genpd->power_off_work is pending before attempting to
queue it up.
Signed-off-by: NRafael J. Wysocki <rjw@sisk.pl>

Kevin points out that if there's a device that can wake up the system
from sleep states, but it doesn't generate wakeup signals by itself
(they are generated on its behalf by other parts of the system) and
it currently is not enabled to wake up the system (that is,
device_may_wakeup() returns "false" for it), we may need to change
its wakeup settings during system suspend (for example, the device
might have been configured to signal remote wakeup from the system's
working state, as needed by runtime PM).  Therefore the generic PM
domains code should invoke the system suspend callbacks provided by
the device's driver, which it doesn't do if the PM domain is powered
off during the system suspend's "prepare" stage.  This is a valid
point.  Moreover, this code also should make sure that system wakeup
devices that are enabled to wake up the system from sleep states and
have to remain active for this purpose are not suspended while the
system is in a sleep state.

To avoid the above issues, make the generic PM domains' .prepare()
routine, pm_genpd_prepare(), force runtime resume of devices whose
system wakeup settings may need to be changed during system suspend
or that should remain active while the system is in a sleep state to
be able to wake it up from that state.
Reported-by: NKevin Hilman <khilman@ti.com>
Signed-off-by: NRafael J. Wysocki <rjw@sisk.pl>

Since every device in a PM domain has its own need_restore
flag, which is set by __pm_genpd_save_device(), there's no need to
walk the domain's device list and restore all devices on an error
from one of the drivers' .runtime_suspend() callbacks.
Signed-off-by: NRafael J. Wysocki <rjw@sisk.pl>

A deadlock may occur if one of the PM domains' .start_device() or
.stop_device() callbacks or a device driver's .runtime_suspend() or
.runtime_resume() callback executed by the core generic PM domain
code uses a "wrong" runtime PM helper function.  This happens, for
example, if .runtime_resume() from one device's driver calls
pm_runtime_resume() for another device in the same PM domain.
A similar situation may take place if a device's parent is in the
same PM domain, in which case the runtime PM framework may execute
pm_genpd_runtime_resume() automatically for the parent (if it is
suspended at the moment).  This, of course, is undesirable, so
the generic PM domains code should be modified to prevent it from
happening.

The runtime PM framework guarantees that pm_genpd_runtime_suspend()
and pm_genpd_runtime_resume() won't be executed in parallel for
the same device, so the generic PM domains code need not worry
about those cases.  Still, it needs to prevent the other possible
race conditions between pm_genpd_runtime_suspend(),
pm_genpd_runtime_resume(), pm_genpd_poweron() and pm_genpd_poweroff()
from happening and it needs to avoid deadlocks at the same time.
To this end, modify the generic PM domains code to relax
synchronization rules so that:

* pm_genpd_poweron() doesn't wait for the PM domain status to
  change from GPD_STATE_BUSY.  If it finds that the status is
  not GPD_STATE_POWER_OFF, it returns without powering the domain on
  (it may modify the status depending on the circumstances).

* pm_genpd_poweroff() returns as soon as it finds that the PM
  domain's status changed from GPD_STATE_BUSY after it's released
  the PM domain's lock.

* pm_genpd_runtime_suspend() doesn't wait for the PM domain status
  to change from GPD_STATE_BUSY after executing the domain's
  .stop_device() callback and executes pm_genpd_poweroff() only
  if pm_genpd_runtime_resume() is not executed in parallel.

* pm_genpd_runtime_resume() doesn't wait for the PM domain status
  to change from GPD_STATE_BUSY after executing pm_genpd_poweron()
  and sets the domain's status to GPD_STATE_BUSY and increments its
  counter of resuming devices (introduced by this change) immediately
  after acquiring the lock.  The counter of resuming devices is then
  decremented after executing __pm_genpd_runtime_resume() for the
  device and the domain's status is reset to GPD_STATE_ACTIVE (unless
  there are more resuming devices in the domain, in which case the
  status remains GPD_STATE_BUSY).

This way, for example, if a device driver's .runtime_resume()
callback executes pm_runtime_resume() for another device in the same
PM domain, pm_genpd_poweron() called by pm_genpd_runtime_resume()
invoked by the runtime PM framework will not block and it will see
that there's nothing to do for it.  Next, the PM domain's lock will
be acquired without waiting for its status to change from
GPD_STATE_BUSY and the device driver's .runtime_resume() callback
will be executed.  In turn, if pm_runtime_suspend() is executed by
one device driver's .runtime_resume() callback for another device in
the same PM domain, pm_genpd_poweroff() executed by
pm_genpd_runtime_suspend() invoked by the runtime PM framework as a
result will notice that one of the devices in the domain is being
resumed, so it will return immediately.
Signed-off-by: NRafael J. Wysocki <rjw@sisk.pl>

Currently, the .start_device() and .stop_device() callbacks from
struct generic_pm_domain() as well as the device drivers' runtime PM
callbacks used by the generic PM domains code are executed under
the generic PM domain lock.  This, unfortunately, is prone to
deadlocks, for example if a device and its parent are boths members
of the same PM domain.  For this reason, it would be better if the
PM domains code didn't execute device callbacks under the lock.

Rework the locking in the generic PM domains code so that the lock
is dropped for the execution of device callbacks.  To this end,
introduce PM domains states reflecting the current status of a PM
domain and such that the PM domain lock cannot be acquired if the
status is GPD_STATE_BUSY.  Make threads attempting to acquire a PM
domain's lock wait until the status changes to either
GPD_STATE_ACTIVE or GPD_STATE_POWER_OFF.

This change by itself doesn't fix the deadlock problem mentioned
above, but the mechanism introduced by it will be used for for this
purpose by a subsequent patch.
Signed-off-by: NRafael J. Wysocki <rjw@sisk.pl>