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

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Message-ID: <20230208175547.GA3065515@roeck-us.net>
Date:   Wed, 8 Feb 2023 09:55:47 -0800
From:   Guenter Roeck <linux@...ck-us.net>
To:     George Cherian <gcherian@...vell.com>
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

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.

Guenter