linux-kernel - Re: [linux-pm] [PATCH v3] PM: add statistics debugfs file for suspend to ram

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Date:	Tue, 9 Aug 2011 22:02:30 +0200
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	yanmin_zhang@...ux.intel.com
Cc:	MyungJoo Ham <myungjoo.ham@...il.com>,
	"Liu, ShuoX" <shuox.liu@...el.com>,
	"linux-pm@...ts.linux-foundation.org" 
	<linux-pm@...ts.linux-foundation.org>,
	"Brown, Len" <len.brown@...el.com>, Greg KH <gregkh@...e.de>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [linux-pm] [PATCH v3] PM: add statistics debugfs file for suspend to ram

On Tuesday, August 09, 2011, Yanmin Zhang wrote:
> On Tue, 2011-08-09 at 13:49 +0900, MyungJoo Ham wrote:
> > On Tue, Aug 9, 2011 at 11:27 AM, Liu, ShuoX <shuox.liu@...el.com> wrote:
> > > From: ShuoX Liu <shuox.liu@...el.com>
> > >
> > > Record S3 failure time about each reason and the latest two failed
> > > devices' names in S3 progress.
> > > We can check it through 'suspend_stats' entry in debugfs.
> > >
> > > The motivation of the patch:
> > >
> > > We are enabling power features on Medfield. 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 and developers
> > > don't know what happens.
> > >
> > > 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. The patch adds suspend_stats under
> > > debugfs for users to check suspend to RAM statistics quickly.
> > >
> > > If not using this patch, we have other methods to get info about
> > > what device fails. One is to turn on  CONFIG_PM_DEBUG, but users
> > > would get too much info and testers need recompile the system.
> > >
> > > In addition, dynamic debug is another good tool to dump debug info.
> > > But it still doesn't match our utilization scenario closely.
> > > 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.
> > >
> > > Thank Greg and Rafael for their great comments.
> > >
> > > Change Log:
> > >  V3: Change some programming styles.
> > >  V2:
> > >        1) Change the sysfs entry to debugfs.
> > >        2) Add some explanation in document file.
> > >
> > > Contribution:
> > >        yanmin_zhang@...ux.intel.com
> > >
> > > Signed-off-by: ShuoX Liu <shuox.liu@...el.com>
> > > ---
> > >  Documentation/power/basic-pm-debugging.txt |   19 +++++++++
> > >  drivers/base/power/main.c                  |   35 ++++++++++++++--
> > >  include/linux/suspend.h                    |   16 +++++++
> > >  kernel/power/main.c                        |   59 ++++++++++++++++++++++++++++
> > >  kernel/power/suspend.c                     |   15 ++++++-
> > >  5 files changed, 136 insertions(+), 8 deletions(-)
> > >
> > 
> > This patch looks very helpful. Great! :)
> > 
> > Anyway, how about including the error value induced by the device
> > along with the device name?
> > For example,
> > 
> > failed_devs:
> >          last_failed: alarm -5
> >                       adc -10
> > 
> > or
> > 
> > failed_devs:
> >          last_failed: alarm
> >                       adc
> >          last_errorno: -5
> >                       -10
> > 
> 
> > Or, even, we may consider including the failed step:
> > failed_devs:
> >          last_failed: alarm
> >                       adc
> >          last_errorno: -5
> >                       -10
> >          last_step: suspend
> >                       suspend_noirq
> > 
> It's a good idea! We would change it to output like above format.

OK, I'm expecting a new version of the patch.

Thanks,
Rafael
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