From: Sai Prakash Ranjan <saiprakash.ranjan@codeaurora.org>
To: Guenter Roeck <linux@roeck-us.net>
Cc: Andy Gross <agross@kernel.org>,
Bjorn Andersson <bjorn.andersson@linaro.org>,
Douglas Anderson <dianders@chromium.org>,
Wim Van Sebroeck <wim@linux-watchdog.org>,
linux-watchdog@vger.kernel.org,
Stephen Boyd <swboyd@chromium.org>,
Matthias Kaehlcke <mka@chromium.org>,
linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org, linux-arm-msm@vger.kernel.org,
Guenter Roeck <groeck7@gmail.com>
Subject: Re: [PATCH] watchdog: qcom: Move suspend/resume to suspend_late/resume_early
Date: Mon, 24 May 2021 09:42:09 +0530 [thread overview]
Message-ID: <ada92dd88c775b5140c397d4cef74f83@codeaurora.org> (raw)
In-Reply-To: <3f76d6cc-df32-6bf3-9971-4ca8f0ee8169@roeck-us.net>
On 2021-05-24 09:33, Guenter Roeck wrote:
> 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@codeaurora.org>
>>>>
>>>> Reviewed-by: Guenter Roeck <linux@roeck-us.net>
>>>>
>>>
>>> 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.
>
Ah I see, thanks for the info.
-Sai
--
QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a
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of Code Aurora Forum, hosted by The Linux Foundation
next prev parent reply other threads:[~2021-05-24 4:12 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-10 20:20 [PATCH] watchdog: qcom: Move suspend/resume to suspend_late/resume_early Sai Prakash Ranjan
2021-03-10 20:23 ` Guenter Roeck
2021-04-20 5:43 ` Sai Prakash Ranjan
2021-05-24 2:38 ` Sai Prakash Ranjan
2021-05-24 4:03 ` Guenter Roeck
2021-05-24 4:12 ` Sai Prakash Ranjan [this message]
2021-03-10 20:27 ` Doug Anderson
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