From: Evgeniy Didin <Evgeniy.Didin@synopsys.com>
To: "andy.shevchenko@gmail.com" <andy.shevchenko@gmail.com>,
"Evgeniy.Didin@synopsys.com" <Evgeniy.Didin@synopsys.com>
Cc: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"Alexey.Brodkin@synopsys.com" <Alexey.Brodkin@synopsys.com>,
"linux-mmc@vger.kernel.org" <linux-mmc@vger.kernel.org>,
"dianders@chromium.org" <dianders@chromium.org>,
"Vineet.Gupta1@synopsys.com" <Vineet.Gupta1@synopsys.com>,
"Eugeniy.Paltsev@synopsys.com" <Eugeniy.Paltsev@synopsys.com>,
"linux-snps-arc@lists.infradead.org"
<linux-snps-arc@lists.infradead.org>,
"stable@vger.kernel.org" <stable@vger.kernel.org>,
"ulf.hansson@linaro.org" <ulf.hansson@linaro.org>
Subject: Re: [PATCH 2/2 v3] mmc: dw_mmc: Fix the CTO overflow calculation for 32-bit systems
Date: Mon, 26 Feb 2018 15:14:21 +0000 [thread overview]
Message-ID: <1519658060.31245.4.camel@synopsys.com> (raw)
In-Reply-To: <CAHp75Vct=jMohCFnn3aoZCAw-Q8=8OOF-nPXh9dfwrWHVPXSfA@mail.gmail.com>
On Mon, 2018-02-26 at 16:39 +0200, Andy Shevchenko wrote:
> On Mon, Feb 26, 2018 at 4:34 PM, Evgeniy Didin
> <Evgeniy.Didin@synopsys.com> wrote:
> > In commit 4c2357f57dd5 ("mmc: dw_mmc: Fix the CTO timeout calculation")
> > have been made changes which can cause multiply overflow for 32-bit systems.
> > The value of cto_ms is lower the drto_ms, but nevertheless overflow can occur.
> > Lets cast this multiply to u64 type which prevents overflow.
> > - cto_ms = DIV_ROUND_UP(MSEC_PER_SEC * cto_clks * cto_div, host->bus_hz);
> > +
> > + cto_ms = DIV_ROUND_UP((u64)MSEC_PER_SEC * cto_clks * cto_div, host->bus_hz);
>
> IIRC, someone commented on this or similar, i.e.
>
> DIV_ROUND_UP_ULL() ?
Switch DIV_ROUND_UP macro to DIV_ROUND_UP_ULL is not reasonable
because overflow happens on multiply and DIV_ROUND_UP_ULL helps
with sum overflow.
--
Best regards,
Evgeniy Didin
next prev parent reply other threads:[~2018-02-26 15:33 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-02-26 14:34 [PATCH 0/2 v3] mmc: dw_mmc: Fix DTO/STO timeout overflow calculation Evgeniy Didin
2018-02-26 14:34 ` [PATCH 1/2 v3] mmc: dw_mmc: Fix the DTO timeout overflow calculation for 32-bit systems Evgeniy Didin
2018-02-26 14:40 ` Andy Shevchenko
2018-02-27 1:14 ` Shawn Lin
2018-03-01 1:22 ` kbuild test robot
2018-02-26 14:34 ` [PATCH 2/2 v3] mmc: dw_mmc: Fix the CTO " Evgeniy Didin
2018-02-26 14:39 ` Andy Shevchenko
2018-02-26 15:14 ` Evgeniy Didin [this message]
2018-02-26 16:53 ` Andy Shevchenko
2018-02-26 17:14 ` Evgeniy Didin
2018-02-26 18:30 ` Andy Shevchenko
2018-02-26 20:27 ` Alexey Brodkin
2018-02-27 3:52 ` Jisheng Zhang
2018-02-27 10:49 ` Andy Shevchenko
2018-02-27 3:02 ` [PATCH 0/2 v3] mmc: dw_mmc: Fix DTO/STO timeout overflow calculation Jisheng Zhang
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