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 X-Spam-Level: X-Spam-Status: No, score=-8.1 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 05DC5C32771 for ; Wed, 15 Jan 2020 16:54:51 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C8C5C2465A for ; Wed, 15 Jan 2020 16:54:50 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="bfCcRraP" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728982AbgAOQyu (ORCPT ); Wed, 15 Jan 2020 11:54:50 -0500 Received: from mail-pf1-f195.google.com ([209.85.210.195]:37209 "EHLO mail-pf1-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726566AbgAOQyu (ORCPT ); Wed, 15 Jan 2020 11:54:50 -0500 Received: by mail-pf1-f195.google.com with SMTP id p14so8788780pfn.4; Wed, 15 Jan 2020 08:54:49 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=sender:date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=x4biuHfD3qt3U+cEUvYuc5XAFxMv7j6Z3eytJc0II1Y=; b=bfCcRraPut1UtBkp6mO1CihzI9YRUJa26KCh/08jw4yRys4sWs3rTpvhwCc0khFiWB FugeJ9vEglq+j+DCq8CqhtNd4aQ6TP2MHC+Ry98PnsxCsVEqvZEnzdF3WL6MHnljR7Cm IqsnBs5c6gji/PaG1YDRkcdQegf88o2oVToeXYNRH1+VsDdARd/Mg9gcEtOXPbETWMH3 IFCijkJ1alVo0uIuRjn0m/fLCon1c2Qp61hA4C0Ko314feIUc3/4kkahpcWRDZTGlX+n pJLPu4fP682Ex0yntbssl5mcBsqquMLHXsTKEf7t/05grPb7obFOWVM/8j6MEd/aGp8V srKQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:sender:date:from:to:cc:subject:message-id :references:mime-version:content-disposition:in-reply-to:user-agent; bh=x4biuHfD3qt3U+cEUvYuc5XAFxMv7j6Z3eytJc0II1Y=; b=U/OrJhwyiKdnINdW2Jbxk8sUIZO+tDKgE9dYxxWiSyWn9c5gzGX7ZtkQczv0tzrZ+2 JHL+0DiVJFDplmD4b+KFd5fGKbTf0O3LIgOs1d4/BSyQ99i3JkIGPGBuqM4j89ZNILXC cL7QNS/0c+y20ayaHApU8xgy77Kf7jt3IoB/khgsxA54XvVdjVOKpqdTI+hPRAcCdrg9 85IzjJAQEfq+6Nj/VfE0pl750pO1t0C+Rbu8xQciRkNNRd2KLkSnqqVZxMp03liZENhq u+Tg2sxZvwbhzLp5FcMWY8IJU1MWOud0/Cco+wTdji4/A44XV2HSRywTx7cpLPJF3Dm+ 7mpw== X-Gm-Message-State: APjAAAUmzneC4pxzdI4Tj5TMWTNvl0JmiiDdWSDFZC+zFD8EF/gEJOrW 2Ycr/Iu0PhezY6iHvFxwvkiBdFhZ X-Google-Smtp-Source: APXvYqzFMwW4qCkVOIV4BudBn7rrS0g2rXrBGLq1kfP81ZvGbuGNrwzm/ijmFrgQFGF9MX2DSZxpSg== X-Received: by 2002:aa7:8749:: with SMTP id g9mr8330925pfo.40.1579107289226; Wed, 15 Jan 2020 08:54:49 -0800 (PST) Received: from localhost ([2600:1700:e321:62f0:329c:23ff:fee3:9d7c]) by smtp.gmail.com with ESMTPSA id a26sm22658998pfo.27.2020.01.15.08.54.47 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Wed, 15 Jan 2020 08:54:48 -0800 (PST) Date: Wed, 15 Jan 2020 08:54:47 -0800 From: Guenter Roeck To: Marco Felsch Cc: support.opensource@diasemi.com, contact@stefanchrist.eu, Adam.Thomson.Opensource@diasemi.com, linux-watchdog@vger.kernel.org, kernel@pengutronix.de, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2] watchdog: da9062: make restart handler atomic safe Message-ID: <20200115165447.GA13912@roeck-us.net> References: <20200115162307.7336-1-m.felsch@pengutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200115162307.7336-1-m.felsch@pengutronix.de> User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-watchdog-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-watchdog@vger.kernel.org On Wed, Jan 15, 2020 at 05:23:07PM +0100, Marco Felsch wrote: > The restart handler is executed during the shutdown phase which is > atomic/irq-less. The i2c framework supports atomic transfers since > commit 63b96983a5dd ("i2c: core: introduce callbacks for atomic > transfers") to address this use case. Using regmap within an atomic > context is allowed only if the regmap type is MMIO and the cache type > 'flat' or no cache is used. Using the i2c_smbus_write_byte_data() > function can be done without additional tests because: > 1) the DA9062 is an i2c-only device and > 2) the i2c framework emulates the smbus protocol if the host adapter > does not support smbus_xfer by using the master_xfer. > > Signed-off-by: Marco Felsch Reviewed-by: Guenter Roeck > --- > Hi, > > This patch is based on Stefan Lengfeld's RFC Patch [1]. > > [1] https://patchwork.ozlabs.org/patch/1085942/ > > Changes: > > v2: > - adapt commit message > - add comment > - make use of i2c_smbus_write_byte_data() > --- > drivers/watchdog/da9062_wdt.c | 10 ++++++---- > 1 file changed, 6 insertions(+), 4 deletions(-) > > diff --git a/drivers/watchdog/da9062_wdt.c b/drivers/watchdog/da9062_wdt.c > index c9b9d6394525..77b6b5336067 100644 > --- a/drivers/watchdog/da9062_wdt.c > +++ b/drivers/watchdog/da9062_wdt.c > @@ -11,6 +11,7 @@ > #include > #include > #include > +#include > #include > #include > #include > @@ -149,12 +150,13 @@ static int da9062_wdt_restart(struct watchdog_device *wdd, unsigned long action, > void *data) > { > struct da9062_watchdog *wdt = watchdog_get_drvdata(wdd); > + struct i2c_client *client = to_i2c_client(wdt->hw->dev); > int ret; > > - ret = regmap_write(wdt->hw->regmap, > - DA9062AA_CONTROL_F, > - DA9062AA_SHUTDOWN_MASK); > - if (ret) > + /* Don't use regmap because it is not atomic safe */ > + ret = i2c_smbus_write_byte_data(client, DA9062AA_CONTROL_F, > + DA9062AA_SHUTDOWN_MASK); > + if (ret < 0) > dev_alert(wdt->hw->dev, "Failed to shutdown (err = %d)\n", > ret); > > -- > 2.20.1 >