diff options
Diffstat (limited to 'Documentation/power')
| -rw-r--r-- | Documentation/power/freezing-of-tasks.txt | 8 | ||||
| -rw-r--r-- | Documentation/power/regulator/machine.txt | 19 | ||||
| -rw-r--r-- | Documentation/power/runtime_pm.txt | 10 |
3 files changed, 27 insertions, 10 deletions
diff --git a/Documentation/power/freezing-of-tasks.txt b/Documentation/power/freezing-of-tasks.txt index 38b57248fd6..316c2ba187f 100644 --- a/Documentation/power/freezing-of-tasks.txt +++ b/Documentation/power/freezing-of-tasks.txt @@ -22,12 +22,12 @@ try_to_freeze_tasks() that sets TIF_FREEZE for all of the freezable tasks and either wakes them up, if they are kernel threads, or sends fake signals to them, if they are user space processes. A task that has TIF_FREEZE set, should react to it by calling the function called refrigerator() (defined in -kernel/power/process.c), which sets the task's PF_FROZEN flag, changes its state +kernel/freezer.c), which sets the task's PF_FROZEN flag, changes its state to TASK_UNINTERRUPTIBLE and makes it loop until PF_FROZEN is cleared for it. Then, we say that the task is 'frozen' and therefore the set of functions handling this mechanism is referred to as 'the freezer' (these functions are -defined in kernel/power/process.c and include/linux/freezer.h). User space -processes are generally frozen before kernel threads. +defined in kernel/power/process.c, kernel/freezer.c & include/linux/freezer.h). +User space processes are generally frozen before kernel threads. It is not recommended to call refrigerator() directly. Instead, it is recommended to use the try_to_freeze() function (defined in @@ -95,7 +95,7 @@ after the memory for the image has been freed, we don't want tasks to allocate additional memory and we prevent them from doing that by freezing them earlier. [Of course, this also means that device drivers should not allocate substantial amounts of memory from their .suspend() callbacks before hibernation, but this -is e separate issue.] +is a separate issue.] 3. The third reason is to prevent user space processes and some kernel threads from interfering with the suspending and resuming of devices. A user space diff --git a/Documentation/power/regulator/machine.txt b/Documentation/power/regulator/machine.txt index b42419b52e4..ce63af0a8e3 100644 --- a/Documentation/power/regulator/machine.txt +++ b/Documentation/power/regulator/machine.txt @@ -16,7 +16,7 @@ initialisation code by creating a struct regulator_consumer_supply for each regulator. struct regulator_consumer_supply { - struct device *dev; /* consumer */ + const char *dev_name; /* consumer dev_name() */ const char *supply; /* consumer supply - e.g. "vcc" */ }; @@ -24,13 +24,13 @@ e.g. for the machine above static struct regulator_consumer_supply regulator1_consumers[] = { { - .dev = &platform_consumerB_device.dev, - .supply = "Vcc", + .dev_name = "dev_name(consumer B)", + .supply = "Vcc", },}; static struct regulator_consumer_supply regulator2_consumers[] = { { - .dev = &platform_consumerA_device.dev, + .dev = "dev_name(consumer A"), .supply = "Vcc", },}; @@ -43,6 +43,7 @@ to their supply regulator :- static struct regulator_init_data regulator1_data = { .constraints = { + .name = "Regulator-1", .min_uV = 3300000, .max_uV = 3300000, .valid_modes_mask = REGULATOR_MODE_NORMAL, @@ -51,13 +52,19 @@ static struct regulator_init_data regulator1_data = { .consumer_supplies = regulator1_consumers, }; +The name field should be set to something that is usefully descriptive +for the board for configuration of supplies for other regulators and +for use in logging and other diagnostic output. Normally the name +used for the supply rail in the schematic is a good choice. If no +name is provided then the subsystem will choose one. + Regulator-1 supplies power to Regulator-2. This relationship must be registered with the core so that Regulator-1 is also enabled when Consumer A enables its supply (Regulator-2). The supply regulator is set by the supply_regulator -field below:- +field below and co:- static struct regulator_init_data regulator2_data = { - .supply_regulator = "regulator_name", + .supply_regulator = "Regulator-1", .constraints = { .min_uV = 1800000, .max_uV = 2000000, diff --git a/Documentation/power/runtime_pm.txt b/Documentation/power/runtime_pm.txt index 0e856088db7..5336149f831 100644 --- a/Documentation/power/runtime_pm.txt +++ b/Documentation/power/runtime_pm.txt @@ -789,6 +789,16 @@ will behave normally, not taking the autosuspend delay into account. Similarly, if the power.use_autosuspend field isn't set then the autosuspend helper functions will behave just like the non-autosuspend counterparts. +Under some circumstances a driver or subsystem may want to prevent a device +from autosuspending immediately, even though the usage counter is zero and the +autosuspend delay time has expired. If the ->runtime_suspend() callback +returns -EAGAIN or -EBUSY, and if the next autosuspend delay expiration time is +in the future (as it normally would be if the callback invoked +pm_runtime_mark_last_busy()), the PM core will automatically reschedule the +autosuspend. The ->runtime_suspend() callback can't do this rescheduling +itself because no suspend requests of any kind are accepted while the device is +suspending (i.e., while the callback is running). + The implementation is well suited for asynchronous use in interrupt contexts. However such use inevitably involves races, because the PM core can't synchronize ->runtime_suspend() callbacks with the arrival of I/O requests. |