linux-kernel - Re: [PATCH 1/2] watchdog: dw_wdt: restart the counter immediately after enabling WDT

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Message-ID: <20140923154501.50dc8111@xhacker>
Date:	Tue, 23 Sep 2014 15:45:01 +0800
From:	Jisheng Zhang <jszhang@...vell.com>
To:	Guenter Roeck <linux@...ck-us.net>
CC:	"wim@...ana.be" <wim@...ana.be>,
	"linux-watchdog@...r.kernel.org" <linux-watchdog@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH 1/2] watchdog: dw_wdt: restart the counter immediately
 after enabling WDT

Dear Guenter,

On Sat, 20 Sep 2014 06:51:56 -0700
Guenter Roeck <linux@...ck-us.net> wrote:

> On 09/18/2014 11:29 PM, Jisheng Zhang wrote:
> > The TOP_INIT may be zero, so the timeout period may be very short after
> > initialization is done, thus the system may be reset soon after enabling.
> > We fix this problem by restarting the counter immediately after enabling
> > WDT.
> >
> > Signed-off-by: Jisheng Zhang <jszhang@...vell.com>
> > ---
> >   drivers/watchdog/dw_wdt.c | 1 +
> >   1 file changed, 1 insertion(+)
> >
> > diff --git a/drivers/watchdog/dw_wdt.c b/drivers/watchdog/dw_wdt.c
> > index 9f21029..ad0619d 100644
> > --- a/drivers/watchdog/dw_wdt.c
> > +++ b/drivers/watchdog/dw_wdt.c
> > @@ -146,6 +146,7 @@ static int dw_wdt_open(struct inode *inode, struct
> > file *filp) dw_wdt_set_top(DW_WDT_MAX_TOP);
> >   		writel(WDOG_CONTROL_REG_WDT_EN_MASK,
> >   		       dw_wdt.regs + WDOG_CONTROL_REG_OFFSET);
> > +		dw_wdt_keepalive();
> >   	}
> >
> >   	dw_wdt_set_next_heartbeat();
> >
> After getting access to the datasheet, I concluded that this fix is wrong
> or at least more risky than necessary. The datasheet states that top_init,
> ie bit 4-7 of the wdt_torr register, needs to be initialized with the
> desired timeout period prior to enabling the watchdog. dw_wdt_set_top()
> sets it to 0 instead, ie to the lowest possible timeout period.
> 

In patch V2, 
I initialize the TOP_INIT when setting TOP in function dw_wdt_set_top(), this
also can fix the "reboot soon" problem. Could you please have a review again?

Thanks,
Jisheng
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