I am required to put some external device (led brightness) into minimal brightness when the system gets to idle.
Please elaborate on "System gets to idle state." Do you mean the system is suspended ? ------- case 1 or the device has moved to idle state? ------- case 2
The control on led brightness value is done as part of dedicated character device which was written for the purpose of brightness control (which uses i2c bus) I wander if this is possible using the linux PM capabilities, and how this should be done. In either case it should be possible as per my understanding. You need to implement it in the appropriate PM handlers. case1 ----> write the appropriate code in driver->pm->suspend case2 ----> write the appropriate code in driver->pm->runtime_idle
Regards, Ayan Kumar Halder
Thanks, Ran
On Fri, Sep 5, 2014 at 7:13 PM, AYAN KUMAR HALDER <ayankumarh@gmail.com> wrote:
When adding some external device to power management, doesn't it need to belong to power domain ( /debug/pm_debug/count ).
Power Domains are decided by system designer. A board can be divided into multiple power domains which can be powered on/off or voltage/current regulated independently as each power domain is controlled by a power regulator.
What is the power domain of external device ? The right person to answer this question will be your system designer. You may look into the board schematics to find out power regulator of your external device. Each power domain is controlled by a power regulator.
It is not necessary for you to consider power domains if you do not wish to power up/down or regulate the voltage /current while running Linux on the board. Another generic way to do runtime-power management of various devices would be to perform clock scaling/gating (assuming you know the clock domains of your system).