From: Guenter Roeck <linux@roeck-us.net>
To: Robin Gong <yibin.gong@nxp.com>,
wim@linux-watchdog.org, shawnguo@kernel.org,
s.hauer@pengutronix.de, festevam@gmail.com
Cc: linux-imx@nxp.com, kernel@pengutronix.de,
linux-watchdog@vger.kernel.org,
linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v1] watchdog: imx2_wdt: clear WDOG_HW_RUNNING before suspend
Date: Mon, 10 May 2021 20:59:25 -0700 [thread overview]
Message-ID: <d5364293-8cba-0d39-aa45-a55c5d6d2af6@roeck-us.net> (raw)
In-Reply-To: <1620732032-7675-1-git-send-email-yibin.gong@nxp.com>
On 5/11/21 4:20 AM, Robin Gong wrote:
> Since watchdog_ping_work is not freezable so that it maybe scheduled before
> imx2_wdt_resume where watchdog clock enabled, hence, kernel will hang in
> imx2_wdt_ping without clock, and then watchdog reset happen. Prevent the
> above case by clearing WDOG_HW_RUNNING before suspend, and restore it with
> ping in imx2_wdt_resume.
>
> Signed-off-by: Robin Gong <yibin.gong@nxp.com>
> ---
> drivers/watchdog/imx2_wdt.c | 8 ++++++++
> 1 file changed, 8 insertions(+)
>
> diff --git a/drivers/watchdog/imx2_wdt.c b/drivers/watchdog/imx2_wdt.c
> index b84f80f..d3751e9 100644
> --- a/drivers/watchdog/imx2_wdt.c
> +++ b/drivers/watchdog/imx2_wdt.c
> @@ -357,6 +357,13 @@ static int __maybe_unused imx2_wdt_suspend(struct device *dev)
> */
> __imx2_wdt_set_timeout(wdog, IMX2_WDT_MAX_TIME);
> imx2_wdt_ping(wdog);
> +
> + /*
> + * clear WDOG_HW_RUNNING to prevent watchdog_ping_work running
> + * before imx2_wdt_resume where clock enabled, otherwise kernel
> + * will hang and watchdog reset happen then.
> + */
> + clear_bit(WDOG_HW_RUNNING, &wdog->status);
> }
>
> clk_disable_unprepare(wdev->clk);
> @@ -386,6 +393,7 @@ static int __maybe_unused imx2_wdt_resume(struct device *dev)
> if (imx2_wdt_is_running(wdev)) {
> imx2_wdt_set_timeout(wdog, wdog->timeout);
> imx2_wdt_ping(wdog);
> + set_bit(WDOG_HW_RUNNING, &wdog->status);
> }
>
> return 0;
>
I really don't like this; it depends on assumptions how the watchdog
core works, and it misuses WDOG_HW_RUNNING to indicate that the clock
is stopped (or that the driver is in suspend mode).
If ping doesn't work with the clock stopped, I think it would be much
better to have a flag indicating that the clock is stopped, and have
the ping function do nothing if it is called with stopped clock
(ie if suspended).
Guenter
_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
next prev parent reply other threads:[~2021-05-11 11:24 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-11 11:20 [PATCH v1] watchdog: imx2_wdt: clear WDOG_HW_RUNNING before suspend Robin Gong
2021-05-11 3:59 ` Guenter Roeck [this message]
2021-05-12 11:34 ` Robin Gong
2021-05-12 14:14 ` Guenter Roeck
2021-05-13 3:49 ` Robin Gong
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=d5364293-8cba-0d39-aa45-a55c5d6d2af6@roeck-us.net \
--to=linux@roeck-us.net \
--cc=festevam@gmail.com \
--cc=kernel@pengutronix.de \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=linux-imx@nxp.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-watchdog@vger.kernel.org \
--cc=s.hauer@pengutronix.de \
--cc=shawnguo@kernel.org \
--cc=wim@linux-watchdog.org \
--cc=yibin.gong@nxp.com \
/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).