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SubjectRe: [PATCH] watchdog: qcom: Move suspend/resume to suspend_late/resume_early
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 <>
>> Reviewed-by: Guenter Roeck <>
> 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 !!

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