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
next prev parent reply other threads:[~2021-05-11 3:59 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
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