linux-kernel - Re: [PATCH v2] watchdog: sbsa_wdog: Make sure the timeout programming is within the limits

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Date:   Thu, 9 Feb 2023 02:09:07 +0000
From:   George Cherian <gcherian@...vell.com>
To:     Guenter Roeck <linux@...ck-us.net>
CC:     "wim@...ux-watchdog.org" <wim@...ux-watchdog.org>,
        "zhangshaokun@...ilicon.com" <zhangshaokun@...ilicon.com>,
        "linux-watchdog@...r.kernel.org" <linux-watchdog@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] watchdog: sbsa_wdog: Make sure the timeout programming
 is within the limits



> -----Original Message-----
> From: Guenter Roeck <groeck7@...il.com> On Behalf Of Guenter Roeck
> Sent: Wednesday, February 8, 2023 11:26 PM
> To: George Cherian <gcherian@...vell.com>
> Cc: wim@...ux-watchdog.org; zhangshaokun@...ilicon.com; linux-
> watchdog@...r.kernel.org; linux-kernel@...r.kernel.org
> Subject: Re: [PATCH v2] watchdog: sbsa_wdog: Make sure the timeout
> programming is within the limits
> 
> ----------------------------------------------------------------------
> On Wed, Feb 08, 2023 at 05:20:34PM +0000, George Cherian wrote:
> >
> >
> > > -----Original Message-----
> > > From: Guenter Roeck <groeck7@...il.com> On Behalf Of Guenter
> Roeck
> > > Sent: Wednesday, February 8, 2023 8:41 PM
> > > To: George Cherian <gcherian@...vell.com>; wim@...ux-watchdog.org;
> > > zhangshaokun@...ilicon.com
> > > Cc: linux-watchdog@...r.kernel.org; linux-kernel@...r.kernel.org
> > > Subject: Re: [PATCH v2] watchdog: sbsa_wdog: Make sure the timeout
> > > programming is within the limits
> > >
> > >
> > > --------------------------------------------------------------------
> > > -- On 2/8/23 00:37, George Cherian wrote:
> > > > Make sure to honour the max_hw_heartbeat_ms while programming
> the
> > > > timeout value to WOR. Clamp the timeout passed to
> > > > sbsa_gwdt_set_timeout() to make sure the programmed value is
> > > > within
> > > the permissible range.
> > > >
> > > > Fixes: abd3ac7902fb ("watchdog: sbsa: Support architecture version
> > > > 1")
> > > >
> > > > Signed-off-by: George Cherian <george.cherian@...vell.com>
> > > > ---
> > > >   drivers/watchdog/sbsa_gwdt.c | 1 +
> > > >   1 file changed, 1 insertion(+)
> > > >
> > > > diff --git a/drivers/watchdog/sbsa_gwdt.c
> > > > b/drivers/watchdog/sbsa_gwdt.c index 9791c74aebd4..ee1039a652f1
> > > 100644
> > > > --- a/drivers/watchdog/sbsa_gwdt.c
> > > > +++ b/drivers/watchdog/sbsa_gwdt.c
> > > > @@ -149,6 +149,7 @@ static int sbsa_gwdt_set_timeout(struct
> > > watchdog_device *wdd,
> > > >   {
> > > >   	struct sbsa_gwdt *gwdt = watchdog_get_drvdata(wdd);
> > > >
> > > > +	timeout = clamp_t(unsigned int, timeout, 1, wdd-
> > > >max_hw_heartbeat_ms
> > > > +/ 1000);
> > > >   	wdd->timeout = timeout;
> > > >
> > >
> > > Wrong order. wdd->timeout should still contain the requested timeout.
> > But then the requested timeout is not being set in HW.
> > Isn't that a disconnect?
> 
> No. The driver is supposed to set a timeout no larger than
> max_hw_heartbeat_ms. The watchdog core then takes care of differences
> between ->timeout (as seen by the user) and max_hw_heartbeat_ms and
> pings the watchdog as needed.
Thanks for the explanation. Will post v3.

-George
> 
> Guenter