From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 31F12C32789 for ; Mon, 22 Aug 2022 08:00:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229756AbiHVIAa (ORCPT ); Mon, 22 Aug 2022 04:00:30 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53834 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232659AbiHVIA3 (ORCPT ); Mon, 22 Aug 2022 04:00:29 -0400 Received: from metis.ext.pengutronix.de (metis.ext.pengutronix.de [IPv6:2001:67c:670:201:290:27ff:fe1d:cc33]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 76AE728713 for ; Mon, 22 Aug 2022 01:00:28 -0700 (PDT) Received: from ptx.hi.pengutronix.de ([2001:67c:670:100:1d::c0]) by metis.ext.pengutronix.de with esmtps (TLS1.3:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1oQ2Lz-0002bL-TJ; Mon, 22 Aug 2022 10:00:11 +0200 Received: from mfe by ptx.hi.pengutronix.de with local (Exim 4.92) (envelope-from ) id 1oQ2Ly-0006TF-A2; Mon, 22 Aug 2022 10:00:10 +0200 Date: Mon, 22 Aug 2022 10:00:10 +0200 From: Marco Felsch To: "Alice Guo (OSS)" 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 , "kernel@pengutronix.de" , "linux-watchdog@vger.kernel.org" Subject: Re: [PATCH 2/7] watchdog: imx7ulp: Add explict memory barrier for unlock sequence Message-ID: <20220822080010.ecdphpm3i26cco5f@pengutronix.de> References: <20220816043643.26569-1-alice.guo@oss.nxp.com> <20220816043643.26569-3-alice.guo@oss.nxp.com> <20220816062330.z2fvurteg337krw2@pengutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: NeoMutt/20180716 X-SA-Exim-Connect-IP: 2001:67c:670:100:1d::c0 X-SA-Exim-Mail-From: mfe@pengutronix.de X-SA-Exim-Scanned: No (on metis.ext.pengutronix.de); SAEximRunCond expanded to false X-PTX-Original-Recipient: linux-watchdog@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-watchdog@vger.kernel.org On 22-08-22, Alice Guo (OSS) wrote: > > -----Original Message----- > > From: Marco Felsch > > Sent: Tuesday, August 16, 2022 2:24 PM > > To: Alice Guo (OSS) > > 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 ; 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 > > > > > > 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. Regards, Marco > > Best Regards, > Alice Guo > > > > > > > > > Suggested-by: Ye Li > > > Signed-off-by: Jacky Bai > > > Signed-off-by: Alice Guo > > > Reviewed-by: Ye Li > > > --- > > > 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 > > > > > > > > > >