From patchwork Wed Jan 15 16:23:07 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Marco Felsch X-Patchwork-Id: 11335277 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id B732E13BD for ; Wed, 15 Jan 2020 16:23:18 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 946442073A for ; Wed, 15 Jan 2020 16:23:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728931AbgAOQXS (ORCPT ); Wed, 15 Jan 2020 11:23:18 -0500 Received: from metis.ext.pengutronix.de ([85.220.165.71]:51307 "EHLO metis.ext.pengutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726562AbgAOQXS (ORCPT ); Wed, 15 Jan 2020 11:23:18 -0500 Received: from dude02.hi.pengutronix.de ([2001:67c:670:100:1d::28] helo=dude02.lab.pengutronix.de) by metis.ext.pengutronix.de with esmtps (TLS1.3:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1irlRq-0004DR-8L; Wed, 15 Jan 2020 17:23:14 +0100 Received: from mfe by dude02.lab.pengutronix.de with local (Exim 4.92) (envelope-from ) id 1irlRp-0002ZC-CI; Wed, 15 Jan 2020 17:23:13 +0100 From: Marco Felsch To: support.opensource@diasemi.com, linux@roeck-us.net, contact@stefanchrist.eu, Adam.Thomson.Opensource@diasemi.com Cc: linux-watchdog@vger.kernel.org, kernel@pengutronix.de, linux-kernel@vger.kernel.org Subject: [PATCH v2] watchdog: da9062: make restart handler atomic safe Date: Wed, 15 Jan 2020 17:23:07 +0100 Message-Id: <20200115162307.7336-1-m.felsch@pengutronix.de> X-Mailer: git-send-email 2.20.1 MIME-Version: 1.0 X-SA-Exim-Connect-IP: 2001:67c:670:100:1d::28 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 Sender: linux-watchdog-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-watchdog@vger.kernel.org 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 Reviewed-by: Stefan Lengfeld Tested-by: Stefan Lengfeld Reviewed-by: Adam Thomson --- 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);