Hi Ran,
Please find my replies as follows:-
> How does the driver invokes moving to idle state ?
The driver uses numerous apis to send its device to idle state. Some
of them are as follows:-
1. pm_runtime_put/pm_runtime_put_sync - which decreases the usage
count and ultimately calls pm_runtime_idle.
2. pm_runtime_idle - which calls the corresponding
driver->runtime_idle after checking the usage count
3. pm_request_idle - calls pm_runtime_idle
Is it the same as
> invoking runtime suspend by the driver ?
In some cases, eg In platform subsystem drivers , runtime_suspend gets
called from runtime_idle. eg Refer drivers/base/platform.c, the
runtime operations assigned are :-
static const struct dev_pm_ops platform_dev_pm_ops = {
.runtime_suspend = pm_generic_runtime_suspend,
.runtime_resume = pm_generic_runtime_resume,
.runtime_idle = pm_generic_runtime_idle,
USE_PLATFORM_PM_SLEEP_OPS
};
Here pm_generic_runtime_idle() after calling the driver specific
runtime_idle api, calls pm_runtime_suspend -->
pm_generic_runtime_suspend ---> driver specific runtime suspend call.
> What is the difference between idle state to runtime suspend ?
I don't clearly understand the difference between idle state and
runtime suspend as in case of most devices (eg platform devices, usb
devices)
, I see that runtime_idle eventually calls runtime_suspend. eg
drivers/usb/core/usb.c , usb_runtime_idle() -----> pm_runtime_autosuspend()
> Are you familiar with any character device example for using PM ?
Check drivers/usb/core/usb.c.
Regards,
Ayan Kumar Halder
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