From: "Alice Guo (OSS)" <alice.guo@oss.nxp.com>
To: Marco Felsch <m.felsch@pengutronix.de>,
"Alice Guo (OSS)" <alice.guo@oss.nxp.com>
Cc: Guenter Roeck <linux@roeck-us.net>,
"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: Wed, 24 Aug 2022 08:40:58 +0000 [thread overview]
Message-ID: <AM6PR04MB6053D8E0A9AD24757095BFB5E2739@AM6PR04MB6053.eurprd04.prod.outlook.com> (raw)
In-Reply-To: <20220824080338.humjny4fabhmx3z7@pengutronix.de>
> -----Original Message-----
> From: Marco Felsch <m.felsch@pengutronix.de>
> Sent: Wednesday, August 24, 2022 4:04 PM
> To: Alice Guo (OSS) <alice.guo@oss.nxp.com>
> Cc: Guenter Roeck <linux@roeck-us.net>; wim@linux-watchdog.org;
> 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
>
> Hi Alice,
>
> On 22-08-24, Alice Guo (OSS) wrote:
>
> ...
>
> > > > > Hi Guenter and Marco,
> > > > >
> > > > > 1. did you see any issues?
> > > > > This WDOG Timer first appeared in i.MX7ULP, no one report issues
> > > > > probably because few people use i.MX7ULP. This issue was found
> > > > > when we did a stress test on it. When we reconfigure the WDOG
> > > > > Timer, there is a certain probability that it reset. The reason
> > > > > for the error is that when WDOG_CS[CMD32EN] is 0, the unlock
> > > > > sequence is two 16-bit writes (0xC520, 0xD928) to the CNT
> > > > > register within 16 bus clocks, and improper unlock sequence causes the
> WDOG to reset.
> > > > > Adding mb() is to guarantee that two 16-bit writes are finished
> > > > > within 16
> > > bus clocks.
> > > >
> > > > After this explanation the whole imx7ulp_wdt_init() seems a bit
> > > > buggy because writel_relaxed() as well as writel() are 32bit access
> functions.
> > > > So the very first thing to do is to enable the 32-bit mode.
> > > >
> > > Agreed. This is much better than having extra code to deal with both
> > > 16-bit and 32-bit access.
> > >
> > > > Also this is a explanation worth to be added to the commit message
> > > > ;)
> > > >
> > >
> > > Definitely. Also, the use of mb(), if it should indeed be needed,
> > > would have to be explained in a code comment.
> > >
> > > Thanks,
> > > Guenter
> >
> > Hi Marco and Guenter,
> >
> > Thank you for your comments. I plan to enable support for 32-bit
> > unlock command write words in bootloader. In this way, there is no
> > need to distinguish whether the unlock command is a 32-bit command or
> > a 16-bit command in driver.
>
> Please don't move this into the bootloader, enabling it within the init seq. is
> just fine. If you move it into the bootloader then you can't ensure that the bit is
> set since there are plenty of bootloaders out there.
>
> As I said, just drop the "16bit" unlock sequence from the init function because
> the unlock is handled just fine in all the watchdog_ops.
>
> Regards,
> Marco
Hi Marco,
Sorry, I did not tell you that all watchdog control bits, timeout value, and window value cannot be set until the watchdog is unlocked. Support for 32-bit unlock command write words in enabled in imx7ulp_wdt_init now.
Best Regards,
Alice Guo
next prev parent reply other threads:[~2022-08-24 8:41 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
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) [this message]
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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