From: Guenter Roeck <linux@roeck-us.net>
To: Sai Prakash Ranjan <saiprakash.ranjan@codeaurora.org>
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
Subject: Re: [PATCH] watchdog: qcom: Move suspend/resume to suspend_late/resume_early
Date: Wed, 10 Mar 2021 12:23:27 -0800 [thread overview]
Message-ID: <20210310202327.GA237124@roeck-us.net> (raw)
In-Reply-To: <20210310202004.1436-1-saiprakash.ranjan@codeaurora.org>
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>
> ---
> drivers/watchdog/qcom-wdt.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/watchdog/qcom-wdt.c b/drivers/watchdog/qcom-wdt.c
> index e38a87ffe5f5..0d2209c5eaca 100644
> --- a/drivers/watchdog/qcom-wdt.c
> +++ b/drivers/watchdog/qcom-wdt.c
> @@ -329,7 +329,9 @@ static int __maybe_unused qcom_wdt_resume(struct device *dev)
> return 0;
> }
>
> -static SIMPLE_DEV_PM_OPS(qcom_wdt_pm_ops, qcom_wdt_suspend, qcom_wdt_resume);
> +static const struct dev_pm_ops qcom_wdt_pm_ops = {
> + SET_LATE_SYSTEM_SLEEP_PM_OPS(qcom_wdt_suspend, qcom_wdt_resume)
> +};
>
> static const struct of_device_id qcom_wdt_of_table[] = {
> { .compatible = "qcom,kpss-timer", .data = &match_data_apcs_tmr },
> --
> QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a member
> of Code Aurora Forum, hosted by The Linux Foundation
>
next prev parent reply other threads:[~2021-03-10 20:24 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 [this message]
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
2021-03-10 20:27 ` Doug Anderson
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20210310202327.GA237124@roeck-us.net \
--to=linux@roeck-us.net \
--cc=agross@kernel.org \
--cc=bjorn.andersson@linaro.org \
--cc=dianders@chromium.org \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=linux-arm-msm@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-watchdog@vger.kernel.org \
--cc=mka@chromium.org \
--cc=saiprakash.ranjan@codeaurora.org \
--cc=swboyd@chromium.org \
--cc=wim@linux-watchdog.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).