From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756894Ab2EaKAr (ORCPT ); Thu, 31 May 2012 06:00:47 -0400 Received: from mail-ee0-f46.google.com ([74.125.83.46]:32928 "EHLO mail-ee0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750976Ab2EaKAq convert rfc822-to-8bit (ORCPT ); Thu, 31 May 2012 06:00:46 -0400 MIME-Version: 1.0 In-Reply-To: <1338282140-11106-1-git-send-email-torne@google.com> References: <1338282140-11106-1-git-send-email-torne@google.com> Date: Thu, 31 May 2012 18:00:44 +0800 Message-ID: Subject: Re: [PATCH] MMC: core: cap MMC card timeouts at 2 seconds. From: Ulf Hansson To: "Torne (Richard Coles)" Cc: cjb@laptop.org, linus.walleij@linaro.org, jh80.chung@samsung.com, linux-mmc@vger.kernel.org, linux-kernel@vger.kernel.org, ben@decadent.org.uk Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Richard, On 29 May 2012 17:02, Torne (Richard Coles) wrote: > From: "Torne (Richard Coles)" > > MMC CSD info can specify very large, ridiculous timeouts, big enough to > overflow timeout_ns on 32-bit machines. This can result in the card > timing out on every operation because the wrapped timeout value is far > too small. > > Fix the overflow by capping the result at 2 seconds.  Cards specifying > longer timeouts are almost certainly insane, and host controllers > generally cannot support timeouts that long in any case. > > 2 seconds should be plenty of time for any card to actually function; > the timeout calculation code is already using 1 second as a "worst case" > timeout for cards running in SPI mode. > > Signed-off-by: Torne (Richard Coles) > --- >  drivers/mmc/core/core.c |   11 ++++++++++- >  1 files changed, 10 insertions(+), 1 deletions(-) > > diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c > index 0b6141d..3b4a9fc 100644 > --- a/drivers/mmc/core/core.c > +++ b/drivers/mmc/core/core.c > @@ -512,7 +512,16 @@ void mmc_set_data_timeout(struct mmc_data *data, const struct mmc_card *card) >        if (data->flags & MMC_DATA_WRITE) >                mult <<= card->csd.r2w_factor; > > -       data->timeout_ns = card->csd.tacc_ns * mult; > +       /* > +        * The timeout in nanoseconds may overflow with some cards. Cap it at > +        * two seconds both to avoid the overflow and also because host > +        * controllers cannot generally generate timeouts that long anyway. > +        */ > +       if (card->csd.tacc_ns <= (2 * NSEC_PER_SEC) / mult) > +               data->timeout_ns = card->csd.tacc_ns * mult; > +       else > +               data->timeout_ns = 2 * NSEC_PER_SEC; > + The above looks OK to me, although if doing this for tacc_ns we might want to do this for tacc_clks as well. Could we include that is this patch as well? >        data->timeout_clks = card->csd.tacc_clks * mult; > >        /* > -- > 1.7.7.3 > > -- > To unsubscribe from this list: send the line "unsubscribe linux-mmc" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at  http://vger.kernel.org/majordomo-info.html Kind regards Ulf Hansson