Hi, Uwe
> Subject: Re: [PATCH] watchdog: imx2_wdt: Drop .remove callback
>
> On Mon, Feb 24, 2020 at 10:51:27AM +0800, Anson Huang wrote:
> > .remove callback implementation doesn' call clk_disable_unprepare()
> > which is buggy, actually, we can just use
> > devm_watchdog_register_device() and
> > devm_add_action_or_reset() to handle all necessary operations for
> > remove action, then .remove callback can be dropped.
> >
> > Signed-off-by: Anson Huang <Anson.Huang@xxxxxxx>
> > ---
> > drivers/watchdog/imx2_wdt.c | 37
> > ++++++++++---------------------------
> > 1 file changed, 10 insertions(+), 27 deletions(-)
> >
> > diff --git a/drivers/watchdog/imx2_wdt.c b/drivers/watchdog/imx2_wdt.c
> > index f8d58bf..1fe472f 100644
> > --- a/drivers/watchdog/imx2_wdt.c
> > +++ b/drivers/watchdog/imx2_wdt.c
> > @@ -244,6 +244,11 @@ static const struct regmap_config
> imx2_wdt_regmap_config = {
> > .max_register = 0x8,
> > };
> >
> > +static void imx2_wdt_action(void *data) {
> > + clk_disable_unprepare(data);
>
> Does this have the effect of stopping the watchdog? Maybe we can have a
> more expressive function name here (imx2_wdt_stop_clk or similar)?
This action is ONLY called when probe failed or device is removed, and if watchdog
is running, the core driver will prevent it from being removed.
>
> Is there some watchdog core policy that tells if the watchdog should be
> stopped on unload?
watchdog_stop_on_unregister() should be called in .probe function to make core
policy stop the watchdog before removing it, but I think this driver does NOT call
it, maybe I should add the API call, need Guenter to help confirm.
>
> > +}
> > +
> > static int __init imx2_wdt_probe(struct platform_device *pdev) {
> > struct device *dev = &pdev->dev;
> > @@ -292,6 +297,10 @@ static int __init imx2_wdt_probe(struct
> platform_device *pdev)
> > if (ret)
> > return ret;
> >
> > + ret = devm_add_action_or_reset(dev, imx2_wdt_action, wdev->clk);
> > + if (ret)
> > + return ret;
> > +
> > regmap_read(wdev->regmap, IMX2_WDT_WRSR, &val);
> > wdog->bootstatus = val & IMX2_WDT_WRSR_TOUT ?
> WDIOF_CARDRESET : 0;
> >
> > @@ -315,32 +324,7 @@ static int __init imx2_wdt_probe(struct
> platform_device *pdev)
> > */
> > regmap_write(wdev->regmap, IMX2_WDT_WMCR, 0);
> >
> > - ret = watchdog_register_device(wdog);
> > - if (ret)
> > - goto disable_clk;
> > -
> > - dev_info(dev, "timeout %d sec (nowayout=%d)\n",
> > - wdog->timeout, nowayout);
>
> Does the core put this info in the kernel log? If not dropping it isn't obviously
> right enough to be done en passant.
This is just an info for user which I think NOT unnecessary, so I drop it in this patch
as well.
>
> > - return 0;
> > -
> > -disable_clk:
> > - clk_disable_unprepare(wdev->clk);
> > - return ret;
> > -}
> > -
> > -static int __exit imx2_wdt_remove(struct platform_device *pdev) -{
> > - struct watchdog_device *wdog = platform_get_drvdata(pdev);
> > - struct imx2_wdt_device *wdev = watchdog_get_drvdata(wdog);
> > -
> > - watchdog_unregister_device(wdog);
> > -
> > - if (imx2_wdt_is_running(wdev)) {
> > - imx2_wdt_ping(wdog);
> > - dev_crit(&pdev->dev, "Device removed: Expect reboot!\n");
> > - }
>
> I also wonder about this one. This changes the timing behaviour and so
> IMHO shouldn't be done as a side effect of a cleanup patch.
Guenter has a comment of "use devm_watchdog_register_device(), and the watchdog subsystem
should prevent removal if the watchdog is running ", so I thought no need to check the watchdog's
status here, but after further check the core code of watchdog_cdev_unregister() function, I ONLY
see it will check whether need to stop watchdog before unregister,
...
1083 if (watchdog_active(wdd) &&
1084 test_bit(WDOG_STOP_ON_UNREGISTER, &wdd->status)) {
1085 watchdog_stop(wdd);
1086 }
Hi, Guenter
Do you think watchdog_stop_on_unregister() should be called in .probe function to
make watchdog stop before unregister?
Thanks,
Anson.
