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@xxxxxxxxxxxxxx> > > > Sent: Tuesday, August 16, 2022 2:24 PM > > > To: Alice Guo (OSS) <alice.guo@xxxxxxxxxxx> > > > Cc: wim@xxxxxxxxxxxxxxxxxx; linux@xxxxxxxxxxxx; shawnguo@xxxxxxxxxx; > > > s.hauer@xxxxxxxxxxxxxx; festevam@xxxxxxxxx; > > > linux-arm-kernel@xxxxxxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; > > > dl-linux-imx <linux-imx@xxxxxxx>; kernel@xxxxxxxxxxxxxx; > > > linux-watchdog@xxxxxxxxxxxxxxx > > > 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@xxxxxxx> > > > > > > > > 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@xxxxxxx> > > > > Signed-off-by: Jacky Bai <ping.bai@xxxxxxx> > > > > Signed-off-by: Alice Guo <alice.guo@xxxxxxx> > > > > Reviewed-by: Ye Li <ye.li@xxxxxxx> > > > > --- > > > > 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 > > > > > > > > > > > > > >
