Re: [PATCH 0/2][RFC] PM / sleep: Expose DPM watchdog timeout to sysfs

[Chen Yu <yu.c.chen@intel.com>]

Hi,
On Thu, Aug 11, 2016 at 08:54:42PM +0200, Pavel Machek wrote:
> Hi!
> 
> > Recently we have a new report that, the harddisk can not
> > resume on time due to firmware issues, and got a kernel
> > panic because of DPM watchdog timeout. Since the default
> > timeout has once been modified from 12 to 60 seconds, we
> > might still encounter new case which requires a longer timeout,
> > so expose the value to sysfs and let the users decide which
> > value is appropriate, meanwhile this can also ease the debugging
> > process.
> > 
> > The first patch is to force DPM watchdog depending on CONFIG_PM_SLEEP,
> > thus the second patch which does the actual work, can use
> > CONFIG_DPM_WATCHDOG safely without checking CONFIG_PM_SLEEP.
> 
> Kernel should just work. User should not have to configure random
> knobs to have working suspend/hibernation.
> 
> We do not want "CONFIG_BREAK_SUSPEND" so I believe we don't want
> "CONFIG_DPM_WATCHDOG". If normal users select it and it breaks their
> system, make it depend on "CONFIG_EXPERT" or hide it in some other
> way or maybe remove it from Kconfig altogether. 
>
> Or maybe CONFIG_DPM_WATCHDOG should contain numeric value that user
> has to select?
> 
Yes, if people select it then they have the risk to break their system,
and the original thought of the patch is to behave like a diagnosis to
make it easier for the users to figure it out, how much time it takes
to suspend/resume a bogus peripheral, without recomping the kernel.
-- currently the timeout value for CONFIG_DPM_WATCHDOG can be adjusted
by menuconfig, but bug reporter might have to recompile the kernel
to confirm, and it takes some time to get a feedback from them, so...

thanks,
Yu