Re: [PATCH] watchdog: qcom: Move suspend/resume to suspend_late/resume_early

[Guenter Roeck]

On 5/23/21 7:38 PM, Sai Prakash Ranjan wrote:
> On 2021-04-20 11:13, Sai Prakash Ranjan wrote:
> > Hi Guenter,
> >
> > On 2021-03-11 01:53, Guenter Roeck wrote:
> > > On Thu, Mar 11, 2021 at 01:50:04AM +0530, Sai Prakash Ranjan wrote:
> > > > During suspend/resume usecases and tests, it is common to see issues
> > > > such as lockups either in suspend path or resume path because of the
> > > > bugs in the corresponding device driver pm handling code. In such cases,
> > > > it is important that watchdog is active to make sure that we either
> > > > receive a watchdog pretimeout notification or a bite causing reset
> > > > instead of a hang causing us to hard reset the machine.
> > > >
> > > > There are good reasons as to why we need this because:
> > > >
> > > > * We can have a watchdog pretimeout governor set to panic in which
> > > >   case we can have a backtrace which would help identify the issue
> > > >   with the particular driver and cause a normal reboot.
> > > >
> > > > * Even in case where there is no pretimeout support, a watchdog
> > > >   bite is still useful because some firmware has debug support to dump
> > > >   CPU core context on watchdog bite for post-mortem analysis.
> > > >
> > > > * One more usecase which comes to mind is of warm reboot. In case we
> > > >   hard reset the target, a cold reboot could be induced resulting in
> > > >   lose of ddr contents thereby losing all the debug info.
> > > >
> > > > Currently, the watchdog pm callback just invokes the usual suspend
> > > > and resume callback which do not have any special ordering in the
> > > > sense that a watchdog can be suspended before the buggy device driver
> > > > suspend callback and watchdog resume can happen after the buggy device
> > > > driver resume callback. This would mean that the watchdog will not be
> > > > active when the buggy driver cause the lockups thereby hanging the
> > > > system. So to make sure this doesn't happen, move the watchdog pm to
> > > > use late/early system pm callbacks which will ensure that the watchdog
> > > > is suspended late and resumed early so that it can catch such issues.
> > > >
> > > > Signed-off-by: Sai Prakash Ranjan <saiprakash.ranjan@xxxxxxxxxxxxxx>
> > >
> > > Reviewed-by: Guenter Roeck <linux@xxxxxxxxxxxx>
> >
> > Gentle Ping. I don't see this in linux-next or linux-watchdog, please let
> > me know if anything is pending from my side.
>
> Gentle Ping !!

It is my watchdog-next branch. At some point Wim will hopefully pick it up.

Guenter