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charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 12/15/22 11:07, Kenneth Sloat wrote: > From: Ken Sloat > > This timer HW supports 8, 16 and 32-bit timer widths. This > driver currently uses a u32 to store the max possible value > of the timer. However, statements perform addition of 2 in > xilinx_pwm_apply() when calculating the period_cycles and > duty_cycles values. Since priv->max is a u32, this will > result in an overflow to 1 which will not only be incorrect > but fail on range comparison. This results in making it > impossible to set the PWM in this timer mode. > > There are two obvious solutions to the current problem: > 1. Cast each instance where overflow occurs to u64. > 2. Change priv->max from a u32 to a u64. > > Solution #1 requires more code modifications, and leaves > opportunity to introduce similar overflows if other math > statements are added in the future. These may also go > undetected if running in non 32-bit timer modes. > > Solution #2 is the much smaller and cleaner approach and > thus the chosen method in this patch. > > This was tested on a Zynq UltraScale+ with multiple > instances of the PWM IP. > > Signed-off-by: Ken Sloat > --- > Changes in v2: > -Update commit comments to explain specifically where this > problem occurs as well as compare solutions. > > --- > include/clocksource/timer-xilinx.h | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/include/clocksource/timer-xilinx.h b/include/clocksource/timer-xilinx.h > index c0f56fe6d22a..d116f18de899 100644 > --- a/include/clocksource/timer-xilinx.h > +++ b/include/clocksource/timer-xilinx.h > @@ -41,7 +41,7 @@ struct regmap; > struct xilinx_timer_priv { > struct regmap *map; > struct clk *clk; > - u32 max; > + u64 max; > }; > > /** Reviewed-by: Sean Anderson _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel 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 B666AC4332F for ; Thu, 15 Dec 2022 16:08:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229795AbiLOQI5 (ORCPT ); Thu, 15 Dec 2022 11:08:57 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40596 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229978AbiLOQIi (ORCPT ); Thu, 15 Dec 2022 11:08:38 -0500 Received: from EUR02-AM0-obe.outbound.protection.outlook.com (mail-am0eur02on2055.outbound.protection.outlook.com [40.107.247.55]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id EF64431DD6 for ; Thu, 15 Dec 2022 08:08:35 -0800 (PST) ARC-Seal: i=1; a=rsa-sha256; s=arcselector9901; d=microsoft.com; cv=none; b=XlA3M+9IDOoSsU8xqVdOFKraBlmtHY5f7aDFh5gBqrQlEXc+Qh8+nLqKhm9PTOmhXTE563C23qmqGYegFIpAJyI7CKBwOqAaOszDK9MFAMDaNEavdYuDFq71pKXjimJvg/t1K+cWVKdNCwb6P3ql9Qaxipl5F7e+NOyQTkgPCbnNvrpSMpcA9+rPe67xtuP8kIWCFJBvs4ECc1J5kx4xKNyeockzRq7n2WVRH6it5DmCHnjjbGfkufFSsgOlywY8D5SCIkwhC5McDtfxtzqGkbrrD6o3IeVqLkHqL9h3Fk/KRapYw4XhfkRkx9uh+qVWqfDtNeT3PxLnK8+N21nGjQ== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=microsoft.com; s=arcselector9901; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-AntiSpam-MessageData-ChunkCount:X-MS-Exchange-AntiSpam-MessageData-0:X-MS-Exchange-AntiSpam-MessageData-1; bh=F9RMwUkW3d6whBW2iOEWFiWCXJrSQiCrBD/vFF20DxI=; b=T+let/Gh6/duj0nEnVeOC78MeAZimyFpjq0U5lzndoBY7s15xsOkby52yJH9jki9+iDxbQqs91FG5SbDK7Qf/RWjwQ5lTh21c2ZyINHbznkaW/7gde7h1jorRHJIyE4DqT3/AF9b6J7DS2VhVUgVR7tetwlidljfxirH3h6O0PnB91+DtJKdc9uD48DRp3LEAhZdtvSDw1OlOz8N8ujIZa/pfbOu8X64Ys0g0opOb075qVCTaiySLgmhHiWsZFzevchIgxmbikJuvz9fJlYAbGr1W8LRAp+KrBqRNUhyKmuT+6Oa8y6cP1ieTZICGfa5u9SG8rJRDudQvaT9tJf6KA== ARC-Authentication-Results: i=1; mx.microsoft.com 1; spf=pass smtp.mailfrom=seco.com; dmarc=pass action=none header.from=seco.com; dkim=pass header.d=seco.com; arc=none DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=seco.com; s=selector1; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=F9RMwUkW3d6whBW2iOEWFiWCXJrSQiCrBD/vFF20DxI=; b=DpnZADL2XcW6VDTS7mbyFhmEYaiqcrTvXfpn8AeXReosv7o9sMCvivmG/AiaH0PhD/LleltmGS7sSbvfu3NyTXuvuffhZ8SeH+PEGN4izh/BwaWo4Y0XesEW7HtwhA0LTT8elHNWQ82lTiDxRStKIqJ8Uy+TxYNGSjSVTGKi3ARXYta3dsaET2JdWvnWhGsX4xHhA0FZUaKv+iyBX0Wm2qIJU3j69V03guwmqhkPV1QGkCy2VmLbMCpl3Cr9lyHdBFM65bQEekW/cZ757Af8UrcFL18DvBWY8sRYyy0yJgY14FkcuHupRG7Vil1KNblDWx7HCRnMqSi1InXi4KpXHg== Authentication-Results: dkim=none (message not signed) header.d=none;dmarc=none action=none header.from=seco.com; Received: from DB9PR03MB8847.eurprd03.prod.outlook.com (2603:10a6:10:3dd::13) by AM9PR03MB7790.eurprd03.prod.outlook.com (2603:10a6:20b:3df::20) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.5924.11; Thu, 15 Dec 2022 16:08:32 +0000 Received: from DB9PR03MB8847.eurprd03.prod.outlook.com ([fe80::2b95:1fe4:5d8f:22fb]) by DB9PR03MB8847.eurprd03.prod.outlook.com ([fe80::2b95:1fe4:5d8f:22fb%6]) with mapi id 15.20.5880.019; Thu, 15 Dec 2022 16:08:32 +0000 Message-ID: <423e3575-e8d2-f100-1f9c-43c195139f6b@seco.com> Date: Thu, 15 Dec 2022 11:08:28 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.4.0 Subject: Re: [v2] pwm: xilinx: Fix u32 overflow issue in 32-bit width PWM mode. Content-Language: en-US To: Kenneth Sloat , "michal.simek@xilinx.com" , "linux-arm-kernel@lists.infradead.org" , "linux-kernel@vger.kernel.org" References: From: Sean Anderson In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-ClientProxiedBy: BLAPR03CA0027.namprd03.prod.outlook.com (2603:10b6:208:32b::32) To DB9PR03MB8847.eurprd03.prod.outlook.com (2603:10a6:10:3dd::13) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: DB9PR03MB8847:EE_|AM9PR03MB7790:EE_ X-MS-Office365-Filtering-Correlation-Id: 06c1e0ce-98d3-4f2b-33dc-08dadeb69cdc X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0; X-Microsoft-Antispam-Message-Info: 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 X-Forefront-Antispam-Report: CIP:255.255.255.255;CTRY:;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:DB9PR03MB8847.eurprd03.prod.outlook.com;PTR:;CAT:NONE;SFS:(13230022)(346002)(396003)(376002)(366004)(39850400004)(136003)(451199015)(6512007)(6486002)(478600001)(26005)(52116002)(186003)(6666004)(53546011)(6506007)(316002)(110136005)(86362001)(31696002)(36756003)(2616005)(38100700002)(38350700002)(83380400001)(44832011)(8936002)(41300700001)(2906002)(31686004)(5660300002)(66476007)(66556008)(8676002)(66946007)(43740500002)(45980500001);DIR:OUT;SFP:1101; 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This > driver currently uses a u32 to store the max possible value > of the timer. However, statements perform addition of 2 in > xilinx_pwm_apply() when calculating the period_cycles and > duty_cycles values. Since priv->max is a u32, this will > result in an overflow to 1 which will not only be incorrect > but fail on range comparison. This results in making it > impossible to set the PWM in this timer mode. > > There are two obvious solutions to the current problem: > 1. Cast each instance where overflow occurs to u64. > 2. Change priv->max from a u32 to a u64. > > Solution #1 requires more code modifications, and leaves > opportunity to introduce similar overflows if other math > statements are added in the future. These may also go > undetected if running in non 32-bit timer modes. > > Solution #2 is the much smaller and cleaner approach and > thus the chosen method in this patch. > > This was tested on a Zynq UltraScale+ with multiple > instances of the PWM IP. > > Signed-off-by: Ken Sloat > --- > Changes in v2: > -Update commit comments to explain specifically where this > problem occurs as well as compare solutions. > > --- > include/clocksource/timer-xilinx.h | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/include/clocksource/timer-xilinx.h b/include/clocksource/timer-xilinx.h > index c0f56fe6d22a..d116f18de899 100644 > --- a/include/clocksource/timer-xilinx.h > +++ b/include/clocksource/timer-xilinx.h > @@ -41,7 +41,7 @@ struct regmap; > struct xilinx_timer_priv { > struct regmap *map; > struct clk *clk; > - u32 max; > + u64 max; > }; > > /** Reviewed-by: Sean Anderson