From mboxrd@z Thu Jan 1 00:00:00 1970 From: htmldeveloper@gmail.com (Peter Teoh) Date: Mon, 15 Sep 2014 00:45:55 +0800 Subject: Any char device example for runtime PM ? In-Reply-To: References: Message-ID: To: kernelnewbies@lists.kernelnewbies.org List-Id: kernelnewbies.lists.kernelnewbies.org On Sat, Sep 13, 2014 at 3:50 PM, Ran Shalit wrote: > On Sat, Sep 13, 2014 at 4:14 AM, Peter Teoh > 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 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 -------------- next part -------------- An HTML attachment was scrubbed... URL: http://lists.kernelnewbies.org/pipermail/kernelnewbies/attachments/20140915/94bce826/attachment.html