lkml.org 
[lkml]   [2021]   [May]   [11]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH v1] watchdog: imx2_wdt: clear WDOG_HW_RUNNING before suspend
From
Date
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

\
 
 \ /
  Last update: 2021-05-11 06:00    [W:0.065 / U:0.504 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site