On Sun, Sep 14, 2014 at 7:45 PM, Peter Teoh <htmldeveloper@gmail.com> wrote:
On Sat, Sep 13, 2014 at 3:50 PM, Ran Shalit <ranshalit@gmail.com> wrote:
On Sat, Sep 13, 2014 at 4:14 AM, Peter Teoh <htmldeveloper@gmail.com> wrote:
please elaborate your requirements. char dev is for I/O to hardware. but runtime PM is for hibernating machine. what is the connection u trying to achieve?
On Mon, Sep 8, 2014 at 1:22 PM, Ran Shalit <ranshalit@gmail.com> wrote:
Hello,
Is there any character device example using runtime PM available ? It is most helpful,
Hi,
Some of the drivers I'm using are char devices, while I only saw platform device registration for runtime PM, so my question stem from this.
As to the system requirement I have, it is as following: 1. make everything as automatic as possible , so that there won't be any need to add any userspace application for the matter. 2. wakeup from all relevant wakeup sources 3. should not use sysfs (it should be disabled from kernel) 4. platform is OMAP3530.
Now, As I understand this far, I have the following options ( requirement 3 above I will ignore, don't know how to handle it yet, and assume for meanwhile that I have sysfs) : 1. use suspend scheme (no runtime PM) 1.a. create some kernel periodic thread who check cpu load and will decide to disable system only if its below some minimum threshold (which should indicate no activity) 1.b. initialize all HW interrupts (gpio, uart, etc) as wakeup sources with this scheme only this thread is responsible for the suspend, and there is no use of the runtime PM, right ?
2. use runtime PM scheme : With this scheme I don't understand how some device will wake the system , or doesn't it need to ? If a driver wakes up maybe it need to deliver some info to system ?
as a general comment, your requirement for PM sounds weird.
a. normally, the linux kernel has its own PM protocol....and it governs which devices to saves states, and restore it later.....there is a hierarchy of calls to be made. and it is a complex daisy chain from devices to higher logical level. but yours never seem to mention or plan to integrate to this infrastructure?
b. hardware PM (sorry, i am a software guy...may be wrong) for microcontroller/CPU normally means different states resulting in different external PINs being disable, and for the least powered state only one or two pins are available to wake up the CP/microcontroller. but when u mentioned so many pins are potential wake up source......then it is not powered down at all.
i am being vague and brief, not to waste time, as this is a big topic, sorry.
-- Regards, Peter Teoh
Hi Peter, Thanks very much for the time, Your answer makes a lot of sense actually. I gave you the requirement I got AS-IS, and some of the difficulties I have, partly stem from the things you meantion in your answer. After this delving and research into this hugh issue of PM, I will defenitely return with feedback about these requirements. I would like to use your knowledge if I may. Is it possible to use scheme b only, i.e. configure it all in low level (HW registers) and not to use any linux mechanism ? Thanks, Ran