From: Guenter Roeck <linux@roeck-us.net>
To: Marco Felsch <m.felsch@pengutronix.de>
Cc: "Alice Guo (OSS)" <alice.guo@oss.nxp.com>,
"wim@linux-watchdog.org" <wim@linux-watchdog.org>,
"shawnguo@kernel.org" <shawnguo@kernel.org>,
"s.hauer@pengutronix.de" <s.hauer@pengutronix.de>,
"festevam@gmail.com" <festevam@gmail.com>,
"linux-arm-kernel@lists.infradead.org"
<linux-arm-kernel@lists.infradead.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
dl-linux-imx <linux-imx@nxp.com>,
"kernel@pengutronix.de" <kernel@pengutronix.de>,
"linux-watchdog@vger.kernel.org" <linux-watchdog@vger.kernel.org>
Subject: Re: [PATCH 2/7] watchdog: imx7ulp: Add explict memory barrier for unlock sequence
Date: Mon, 22 Aug 2022 07:03:47 -0700 [thread overview]
Message-ID: <20220822140347.GA4087281@roeck-us.net> (raw)
In-Reply-To: <20220822080010.ecdphpm3i26cco5f@pengutronix.de>
On Mon, Aug 22, 2022 at 10:00:10AM +0200, Marco Felsch wrote:
> On 22-08-22, Alice Guo (OSS) wrote:
> > > -----Original Message-----
> > > From: Marco Felsch <m.felsch@pengutronix.de>
> > > Sent: Tuesday, August 16, 2022 2:24 PM
> > > To: Alice Guo (OSS) <alice.guo@oss.nxp.com>
> > > Cc: wim@linux-watchdog.org; linux@roeck-us.net; shawnguo@kernel.org;
> > > s.hauer@pengutronix.de; festevam@gmail.com;
> > > linux-arm-kernel@lists.infradead.org; linux-kernel@vger.kernel.org;
> > > dl-linux-imx <linux-imx@nxp.com>; kernel@pengutronix.de;
> > > linux-watchdog@vger.kernel.org
> > > Subject: Re: [PATCH 2/7] watchdog: imx7ulp: Add explict memory barrier for
> > > unlock sequence
> > >
> > > On 22-08-16, Alice Guo (OSS) wrote:
> > > > From: Jacky Bai <ping.bai@nxp.com>
> > > >
> > > > Add explict memory barrier for the wdog unlock sequence.
> > >
> > > Did you inspected any failures? It's not enough to say what you did, you need
> > > to specify the why as well.
> > >
> > > Regards,
> > > Marco
> >
> > Hi,
> >
> > Two 16-bit writes of unlocking the Watchdog should be completed within a certain time. The first mb() is used to ensure that previous instructions are completed.
> > The second mb() is used to ensure that the unlock sequence cannot be affected by subsequent instructions. The reason will be added in the commit log of v2.
>
> Hi,
>
> I know what memory barriers are. My question was, did you see any
> issues? Since the driver is used mainline and no one reported issues.
>
> Also just don't use the *_relaxed() versions is more common, than adding
> mb() calls around *_relaxed() versions.
>
Agreed with both. The series is a bit short in explaining _why_ the
changes are made.
Guenter
> Regards,
> Marco
>
> >
> > Best Regards,
> > Alice Guo
> >
> > >
> > > >
> > > > Suggested-by: Ye Li <ye.li@nxp.com>
> > > > Signed-off-by: Jacky Bai <ping.bai@nxp.com>
> > > > Signed-off-by: Alice Guo <alice.guo@nxp.com>
> > > > Reviewed-by: Ye Li <ye.li@nxp.com>
> > > > ---
> > > > drivers/watchdog/imx7ulp_wdt.c | 4 ++++
> > > > 1 file changed, 4 insertions(+)
> > > >
> > > > diff --git a/drivers/watchdog/imx7ulp_wdt.c
> > > > b/drivers/watchdog/imx7ulp_wdt.c index 014f497ea0dc..b8ac0cb04d2f
> > > > 100644
> > > > --- a/drivers/watchdog/imx7ulp_wdt.c
> > > > +++ b/drivers/watchdog/imx7ulp_wdt.c
> > > > @@ -179,9 +179,13 @@ static int imx7ulp_wdt_init(void __iomem *base,
> > > unsigned int timeout)
> > > > int ret;
> > > >
> > > > local_irq_disable();
> > > > +
> > > > + mb();
> > > > /* unlock the wdog for reconfiguration */
> > > > writel_relaxed(UNLOCK_SEQ0, base + WDOG_CNT);
> > > > writel_relaxed(UNLOCK_SEQ1, base + WDOG_CNT);
> > > > + mb();
> > > > +
> > > > ret = imx7ulp_wdt_wait(base, WDOG_CS_ULK);
> > > > if (ret)
> > > > goto init_out;
> > > > --
> > > > 2.17.1
> > > >
> > > >
> > > >
> >
next prev parent reply other threads:[~2022-08-22 14:03 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-08-16 4:36 [PATCH 0/7] watchdog: imx7ulp_wdt: update i.MX7ULP WDOG timer driver Alice Guo (OSS)
2022-08-16 4:36 ` [PATCH 1/7] watchdog: imx7ulp: Move suspend/resume to noirq phase Alice Guo (OSS)
2022-08-16 4:36 ` [PATCH 2/7] watchdog: imx7ulp: Add explict memory barrier for unlock sequence Alice Guo (OSS)
2022-08-16 6:23 ` Marco Felsch
2022-08-22 7:49 ` Alice Guo (OSS)
2022-08-22 8:00 ` Marco Felsch
2022-08-22 14:03 ` Guenter Roeck [this message]
2022-08-23 5:38 ` Alice Guo (OSS)
2022-08-23 9:10 ` Marco Felsch
2022-08-23 12:02 ` Guenter Roeck
2022-08-24 6:24 ` Alice Guo (OSS)
2022-08-24 8:03 ` Marco Felsch
2022-08-24 8:40 ` Alice Guo (OSS)
2022-08-24 9:06 ` Marco Felsch
2022-08-24 10:05 ` Alice Guo (OSS)
2022-08-25 7:50 ` Marco Felsch
2022-08-25 8:08 ` Alice Guo (OSS)
2022-08-25 9:01 ` Marco Felsch
2022-08-25 10:11 ` Alice Guo (OSS)
2022-08-16 4:36 ` [PATCH 3/7] watchdog: imx7ulp_wdt: Check CMD32EN in wdog init Alice Guo (OSS)
2022-08-22 14:05 ` Guenter Roeck
2022-08-23 5:46 ` Alice Guo (OSS)
2022-08-23 12:05 ` Guenter Roeck
2022-08-16 4:36 ` [PATCH 4/7] watchdog: imx7ulp_wdt: Fix RCS timeout issue Alice Guo (OSS)
2022-08-22 14:09 ` Guenter Roeck
2022-08-23 5:59 ` Alice Guo (OSS)
2022-08-23 12:06 ` Guenter Roeck
2022-08-24 6:44 ` Alice Guo (OSS)
2022-08-16 4:36 ` [PATCH 5/7] watchdog: imx7ulp_wdt: Handle wdog reconfigure failure Alice Guo (OSS)
2022-08-16 4:36 ` [PATCH 6/7] watchdog: imx7ulp_wdt: init wdog when it was active Alice Guo (OSS)
2022-08-16 4:36 ` [PATCH 7/7] watchdog: imx93: add watchdog timer on imx93 Alice Guo (OSS)
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