From patchwork Tue Aug 27 11:28:47 2013 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Josh Wu X-Patchwork-Id: 2850139 Return-Path: X-Original-To: patchwork-linux-arm@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork2.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.19.201]) by patchwork2.web.kernel.org (Postfix) with ESMTP id BD1A2BF546 for ; Tue, 27 Aug 2013 11:30:31 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id A15592017D for ; Tue, 27 Aug 2013 11:30:30 +0000 (UTC) Received: from casper.infradead.org (casper.infradead.org [85.118.1.10]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 21B6D200E0 for ; Tue, 27 Aug 2013 11:30:29 +0000 (UTC) Received: from merlin.infradead.org ([2001:4978:20e::2]) by casper.infradead.org with esmtps (Exim 4.80.1 #2 (Red Hat Linux)) id 1VEHTU-00051m-Rv; Tue, 27 Aug 2013 11:30:17 +0000 Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.80.1 #2 (Red Hat Linux)) id 1VEHTN-0000Xt-ID; Tue, 27 Aug 2013 11:30:09 +0000 Received: from newsmtp5.atmel.com ([204.2.163.5] helo=sjogate2.atmel.com) by merlin.infradead.org with esmtp (Exim 4.80.1 #2 (Red Hat Linux)) id 1VEHSz-0000Tp-OY for linux-arm-kernel@lists.infradead.org; Tue, 27 Aug 2013 11:29:47 +0000 Received: from localhost.localdomain ([10.217.11.52]) by sjogate2.atmel.com (8.13.6/8.13.6) with ESMTP id r7RBMrBD021976; Tue, 27 Aug 2013 04:23:04 -0700 (PDT) From: Josh Wu To: jic23@cam.ac.uk Subject: [PATCH v3 1/6] iio: at91: fix adc_clk overflow Date: Tue, 27 Aug 2013 19:28:47 +0800 Message-Id: <1377602932-1899-2-git-send-email-josh.wu@atmel.com> X-Mailer: git-send-email 1.7.10 In-Reply-To: <1377602932-1899-1-git-send-email-josh.wu@atmel.com> References: <1377602932-1899-1-git-send-email-josh.wu@atmel.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20130827_072946_256464_1866D031 X-CRM114-Status: GOOD ( 10.49 ) X-Spam-Score: -4.4 (----) Cc: thomas.petazzoni@free-electrons.com, mark.rutland@arm.com, linux-iio@vger.kernel.org, nicolas.ferre@atmel.com, b.brezillon@overkiz.com, Josh Wu , maxime.ripard@free-electrons.com, plagnioj@jcrosoft.com, linux-arm-kernel@lists.infradead.org X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , MIME-Version: 1.0 Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org X-Spam-Status: No, score=-6.7 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_MED, RP_MATCHES_RCVD, UNPARSEABLE_RELAY autolearn=unavailable version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP The adc_clk variable is currently defined using a 32-bits unsigned integer, which will overflow under some very valid range of operations. Such overflow will occur if, for example, the parent clock is set to a 20MHz frequency and the ADC startup time is larger than 215ns. To fix this, introduce an intermediate variable holding the clock rate in kHz. Signed-off-by: Josh Wu Acked-by: Maxime Ripard --- v1 --> v2: refined the commit message. drivers/iio/adc/at91_adc.c | 11 ++++++----- 1 file changed, 6 insertions(+), 5 deletions(-) diff --git a/drivers/iio/adc/at91_adc.c b/drivers/iio/adc/at91_adc.c index b6db6a0..9cf8ab5 100644 --- a/drivers/iio/adc/at91_adc.c +++ b/drivers/iio/adc/at91_adc.c @@ -582,7 +582,7 @@ static const struct iio_info at91_adc_info = { static int at91_adc_probe(struct platform_device *pdev) { - unsigned int prsc, mstrclk, ticks, adc_clk, shtim; + unsigned int prsc, mstrclk, ticks, adc_clk, adc_clk_khz, shtim; int ret; struct iio_dev *idev; struct at91_adc_state *st; @@ -680,6 +680,7 @@ static int at91_adc_probe(struct platform_device *pdev) */ mstrclk = clk_get_rate(st->clk); adc_clk = clk_get_rate(st->adc_clk); + adc_clk_khz = adc_clk / 1000; prsc = (mstrclk / (2 * adc_clk)) - 1; if (!st->startup_time) { @@ -693,15 +694,15 @@ static int at91_adc_probe(struct platform_device *pdev) * defined in the electrical characteristics of the board, divided by 8. * The formula thus is : Startup Time = (ticks + 1) * 8 / ADC Clock */ - ticks = round_up((st->startup_time * adc_clk / - 1000000) - 1, 8) / 8; + ticks = round_up((st->startup_time * adc_clk_khz / + 1000) - 1, 8) / 8; /* * a minimal Sample and Hold Time is necessary for the ADC to guarantee * the best converted final value between two channels selection * The formula thus is : Sample and Hold Time = (shtim + 1) / ADCClock */ - shtim = round_up((st->sample_hold_time * adc_clk / - 1000000) - 1, 1); + shtim = round_up((st->sample_hold_time * adc_clk_khz / + 1000) - 1, 1); reg = AT91_ADC_PRESCAL_(prsc) & AT91_ADC_PRESCAL; reg |= AT91_ADC_STARTUP_(ticks) & AT91_ADC_STARTUP;