Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754401Ab1BXMZ3 (ORCPT ); Thu, 24 Feb 2011 07:25:29 -0500 Received: from mga02.intel.com ([134.134.136.20]:13568 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753730Ab1BXMZ1 convert rfc822-to-8bit (ORCPT ); Thu, 24 Feb 2011 07:25:27 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.62,217,1297065600"; d="scan'208";a="712723488" From: "Dong, Chuanxiao" To: Marc Koschewski CC: "linux-mmc@vger.kernel.org" , "cjb@laptop.org" , "adrian.hunter@nokia.com" , "linus.walleij@linaro.org" , "linux-kernel@vger.kernel.org" Date: Thu, 24 Feb 2011 20:25:21 +0800 Subject: RE: [PATCH 1/1]mmc: fix division by zero when calculate mmc erase time Thread-Topic: [PATCH 1/1]mmc: fix division by zero when calculate mmc erase time Thread-Index: AcvUHYf3B4bLYYL8TyGquNztNe0wUAAABx6g Message-ID: <5D8008F58939784290FAB48F5497519835CE59FE57@shsmsx502.ccr.corp.intel.com> References: <20110224111801.GA7169@intel.com> <20110224113756.GB7260@marc.osknowledge.org> <5D8008F58939784290FAB48F5497519835CE59FE52@shsmsx502.ccr.corp.intel.com> <20110224122235.GC7260@marc.osknowledge.org> In-Reply-To: <20110224122235.GC7260@marc.osknowledge.org> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: acceptlanguage: en-US Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 8BIT MIME-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3044 Lines: 78 > -----Original Message----- > From: Marc Koschewski [mailto:marc@osknowledge.org] > Sent: Thursday, February 24, 2011 8:23 PM > To: Dong, Chuanxiao > Cc: linux-mmc@vger.kernel.org; cjb@laptop.org; adrian.hunter@nokia.com; > linus.walleij@linaro.org; linux-kernel@vger.kernel.org > Subject: Re: [PATCH 1/1]mmc: fix division by zero when calculate mmc erase time > > * Dong, Chuanxiao [2011-02-24 20:09:59 +0800]: > > > > > > > > -----Original Message----- > > > From: Marc Koschewski [mailto:marc@osknowledge.org] > > > Sent: Thursday, February 24, 2011 7:38 PM > > > To: Dong, Chuanxiao > > > Cc: linux-mmc@vger.kernel.org; cjb@laptop.org; adrian.hunter@nokia.com; > > > linus.walleij@linaro.org; linux-kernel@vger.kernel.org > > > Subject: Re: [PATCH 1/1]mmc: fix division by zero when calculate mmc erase > time > > > > > > Hi, > > > > > > * Chuanxiao Dong [2011-02-24 19:18:01 +0800]: > > > > > > > Since if clock gating feature is enabled, the clock frequency may be zero when > > > > host clock is gated. In such scenario, mmc_set_mmc_erase_timeout() may > have a > > > > division by zero bug. > > > > > > > > So this patch used mmc_host_clk_rate() to fix this. > > > > > > > > Signed-off-by: Chuanxiao Dong > > > > --- > > > > drivers/mmc/core/core.c | 10 ++++++++-- > > > > 1 files changed, 8 insertions(+), 2 deletions(-) > > > > > > > > diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c > > > > index 34a7e8c..12d0eb8 100644 > > > > --- a/drivers/mmc/core/core.c > > > > +++ b/drivers/mmc/core/core.c > > > > @@ -1201,8 +1201,14 @@ static void mmc_set_mmc_erase_timeout(struct > > > mmc_card *card, > > > > * less but not that much less, so fudge it by multiplying by 2. > > > > */ > > > > timeout_clks <<= 1; > > > > - timeout_us += (timeout_clks * 1000) / > > > > - (card->host->ios.clock / 1000); > > > > + > > > > + /* > > > > + * at this moment, host controller maybe clock gated, so make > > > > + * sure we can get a correct host clock freq. > > > > + */ > > > > + if (mmc_host_clk_rate(card->host)) > > > > + timeout_us += (timeout_clks * 1000) / > > > > + (mmc_host_clk_rate(card->host) / 1000); > > > > > > Why don't you just reuse mmc_host_clk_rate()'s result instead of calling it > twice? > > This is a incline function and just return host->ios.clock. Reuse > mmc_host_clk_rate()'s result need to add a new variable to save the value. > > It's not inline on trunk and it spinlocks. > > drivers/mmc/core/host.c:195 > > 194 */ > 195 unsigned int mmc_host_clk_rate(struct mmc_host *host) > 196 { OK. With the clock gating framework enabled... I agree. So, what do you think? Add a new variable is better? Thanks Chuanxiao -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/