Re: [PATCH] PM: add statistics sysfs file for suspend to ram

[Yanmin Zhang <yanmin_zhang@linux.intel.com>]

On Fri, 2011-08-05 at 21:20 +0200, Rafael J. Wysocki wrote:
> On Friday, August 05, 2011, Yanmin Zhang wrote:
> > On Fri, 2011-08-05 at 09:57 +0800, Liu, ShuoX wrote:
> > > > On Thursday, August 04, 2011, Greg KH wrote:
> > > > > On Thu, Aug 04, 2011 at 01:13:38PM +0800, Liu, ShuoX wrote:
> > > > > > >From a906b0b5b4ff3414ceb9fc7a69a3d7c9d66e46b1 Mon Sep 17
> > > > 00:00:00 2001
> > > > > > From: ShuoX Liu <shuox.liu@intel.com>
> > > > > > Date: Thu, 28 Jul 2011 10:54:22 +0800
> > > > > > Subject: [PATCH] PM: add statistics sysfs file for suspend to ram.
> > > > >
> > > > > What's this stuff here for?  That's not needed (hint, I would have to
> > > > > edit it out by hand to be able to apply this patch.)
> > > > >
> > > > > Thanks for resending a version that passes checkpatch.pl and could be
> > > > > applied, but all of my previous comments still stand.  This patch, as
> > > > > is, is totally unacceptable.
> > > > 
> > > > Agreed, plus I'd like to know the motivation behind it.  That is, we have
> > > > quite a few debug facilities in that code, so why are they insufficient?
> > Thanks Greg, Rafael. We are changing the patch based on your comments.
> > 
> > > 
> > > Some explanation from Yanmin,
> > > "We are enabling power features on Medfield. Some testers and developers
> > > complain they don't know if system tries suspend-2-ram, and what device 
> > > fails to suspend. They need such info for a quick check. If turning on 
> > > CONFIG_PM_DEBUG, we get too much info and testers need recompile 
> > > the system.
> > Comparing with PC/notebook, a mobile enters/exits suspend-2-ram (we call it s3 on
> > Medfield) far more frequently. If it can't enter suspend-2-ram in time, the power
> > might be used up soon.
> > 
> > We often find sometimes, a device suspend fails. Then, system retries s3 over
> > and over again. As display is off, testers/developers don't know what happens.
> > Teh system 
> > 
> > With the patch, we could know what the bad device is.
> > 
> > The patch doesn't hurt performance as it's just statistics collector.
> > 
> > CONFIG_PM_DEBUG is very useful for finer investigation about what happens behind. What
> > we provide by the patch is to analyze the issues quickly, even by an ordinary tester.
> 
> Well, what about using dynamic debug?
Thanks for the nice pointer. I checked dynamic debug. It's really a good debug tool.
With the dynamic debug:
1) user need write a user space parser to process the syslog output;
2) Our testing scenario is we leave the mobile for at least hours. Then, check its status.
No serial console available during the testing. One is because console would be suspended,
and the other is serial console connecting with spi or HSU devices would consume power. These
devices are powered off at suspend-2-ram.

Below is an example output of the statistics from my mobile (we are changing the output
from sysfs to debugfs now):
#adb shell cat /sys/power/suspend_stats
success: 5
fail: 1
failed_freeze: 0
failed_prepare: 0
failed_suspend: 1
failed_suspend_noirq: 0
failed_resume: 0
failed_resume_noirq: 0
failed_devs:
  last_failed:	alarm