From patchwork Thu Mar 2 17:31:12 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Alexandre Belloni X-Patchwork-Id: 9601203 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id E4E9F60429 for ; Thu, 2 Mar 2017 17:34:28 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id D849D28599 for ; Thu, 2 Mar 2017 17:34:28 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id CC209285BE; Thu, 2 Mar 2017 17:34:28 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-1.9 required=2.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID autolearn=ham version=3.3.1 Received: from bombadil.infradead.org (bombadil.infradead.org [65.50.211.133]) (using TLSv1.2 with cipher AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.wl.linuxfoundation.org (Postfix) with ESMTPS id 4DF3E28599 for ; Thu, 2 Mar 2017 17:34:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:MIME-Version:References:In-Reply-To: Message-Id:Date:Subject:To:From:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=rEvbRj/XtVUGyNiFUdP+t4XXNSfos/jjtGInYg0zhg4=; b=XheB9D/DuQCGr0 1dBMfmQSXM7HhpHwW4dleLVPfPgnY0raHGQWS+0sqtTaIi89I4gWWCvUONiZQwtxUKbNvq+Zh5PzJ dHAo6aAdz5n/ewybPj1qU3+YnVuyrXu+QW4BdiqFfd4nXxSnWBgM3pD7Pk+ZEz/YgGP5QcrYpHM4r xCj3xIt84U6rFqgWskpZ2epFYHseb9i9vyoFblj+DyVUt65WhMWh5V4qGuMrLfibToaEA3DdmOpHB u7hDWfWJF5X6fNVC/odyWcyHnrp7CUQPYM6OQDBVHb54j9E9nqA5hfQ6erAkbcjRIFTuwg2dkxY2R iiSav7Scjuu9+ZoF4a4A==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.87 #1 (Red Hat Linux)) id 1cjUcV-0006Sf-Q1; Thu, 02 Mar 2017 17:34:27 +0000 Received: from mail.free-electrons.com ([62.4.15.54]) by bombadil.infradead.org with esmtp (Exim 4.87 #1 (Red Hat Linux)) id 1cjUZs-00058V-As for linux-arm-kernel@lists.infradead.org; Thu, 02 Mar 2017 17:31:48 +0000 Received: by mail.free-electrons.com (Postfix, from userid 110) id 8FADD207F4; Thu, 2 Mar 2017 18:31:19 +0100 (CET) Received: from localhost (unknown [88.191.26.124]) by mail.free-electrons.com (Postfix) with ESMTPSA id 6BAE6206E1; Thu, 2 Mar 2017 18:31:19 +0100 (CET) From: Alexandre Belloni To: Guenter Roeck Subject: [PATCH 2/4] watchdog: sama5d4: fix race condition Date: Thu, 2 Mar 2017 18:31:12 +0100 Message-Id: <20170302173114.28508-3-alexandre.belloni@free-electrons.com> X-Mailer: git-send-email 2.11.0 In-Reply-To: <20170302173114.28508-1-alexandre.belloni@free-electrons.com> References: <20170302173114.28508-1-alexandre.belloni@free-electrons.com> MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20170302_093144_701802_7DF17660 X-CRM114-Status: GOOD ( 13.74 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-watchdog@vger.kernel.org, Wenyou.Yang@microchip.com, linux-kernel@vger.kernel.org, Nicolas Ferre , Wim Van Sebroeck , Alexandre Belloni , linux-arm-kernel@lists.infradead.org Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org X-Virus-Scanned: ClamAV using ClamSMTP WDT_MR and WDT_CR must not updated within three slow clock periods after the last ping (write to WDT_CR or WDT_MR). Ensure enough time has elapsed before writing those registers. wdt_write() waits for 4 periods to ensure at least 3 edges are seen by the IP. Signed-off-by: Alexandre Belloni Reviewed-by: Guenter Roeck Acked-by: Wenyou.Yang --- drivers/watchdog/sama5d4_wdt.c | 33 +++++++++++++++++++++++++++++---- 1 file changed, 29 insertions(+), 4 deletions(-) diff --git a/drivers/watchdog/sama5d4_wdt.c b/drivers/watchdog/sama5d4_wdt.c index 5cee20caca78..362fd229786d 100644 --- a/drivers/watchdog/sama5d4_wdt.c +++ b/drivers/watchdog/sama5d4_wdt.c @@ -6,6 +6,7 @@ * Licensed under GPLv2. */ +#include #include #include #include @@ -29,6 +30,7 @@ struct sama5d4_wdt { struct watchdog_device wdd; void __iomem *reg_base; u32 mr; + unsigned long last_ping; }; static int wdt_timeout = WDT_DEFAULT_TIMEOUT; @@ -49,8 +51,29 @@ MODULE_PARM_DESC(nowayout, #define wdt_read(wdt, field) \ readl_relaxed((wdt)->reg_base + (field)) -#define wdt_write(wtd, field, val) \ - writel_relaxed((val), (wdt)->reg_base + (field)) +/* 4 slow clock periods is 4/32768 = 122.07µs*/ +#define WDT_DELAY usecs_to_jiffies(123) + +static void wdt_write(struct sama5d4_wdt *wdt, u32 field, u32 val) +{ + /* + * WDT_CR and WDT_MR must not be modified within three slow clock + * periods following a restart of the watchdog performed by a write + * access in WDT_CR. + */ + while (time_before(jiffies, wdt->last_ping + WDT_DELAY)) + usleep_range(30, 125); + writel_relaxed(val, wdt->reg_base + field); + wdt->last_ping = jiffies; +} + +static void wdt_write_nosleep(struct sama5d4_wdt *wdt, u32 field, u32 val) +{ + if (time_before(jiffies, wdt->last_ping + WDT_DELAY)) + udelay(123); + writel_relaxed(val, wdt->reg_base + field); + wdt->last_ping = jiffies; +} static int sama5d4_wdt_start(struct watchdog_device *wdd) { @@ -164,11 +187,12 @@ static int sama5d4_wdt_init(struct sama5d4_wdt *wdt) * Else, we have to disable it properly. */ if (wdt_enabled) { - wdt_write(wdt, AT91_WDT_MR, wdt->mr); + wdt_write_nosleep(wdt, AT91_WDT_MR, wdt->mr); } else { reg = wdt_read(wdt, AT91_WDT_MR); if (!(reg & AT91_WDT_WDDIS)) - wdt_write(wdt, AT91_WDT_MR, reg | AT91_WDT_WDDIS); + wdt_write_nosleep(wdt, AT91_WDT_MR, + reg | AT91_WDT_WDDIS); } return 0; } @@ -193,6 +217,7 @@ static int sama5d4_wdt_probe(struct platform_device *pdev) wdd->ops = &sama5d4_wdt_ops; wdd->min_timeout = MIN_WDT_TIMEOUT; wdd->max_timeout = MAX_WDT_TIMEOUT; + wdt->last_ping = jiffies; watchdog_set_drvdata(wdd, wdt);