linux-kernel - Re: [PATCH 2/2 v3] mmc: dw_mmc: Fix the CTO overflow calculation for 32-bit systems

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Message-ID: <CAHp75Vct=jMohCFnn3aoZCAw-Q8=8OOF-nPXh9dfwrWHVPXSfA@mail.gmail.com>
Date:   Mon, 26 Feb 2018 16:39:55 +0200
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Evgeniy Didin <Evgeniy.Didin@...opsys.com>
Cc:     linux-mmc@...r.kernel.org,
        Alexey Brodkin <Alexey.Brodkin@...opsys.com>,
        Eugeniy Paltsev <Eugeniy.Paltsev@...opsys.com>,
        Douglas Anderson <dianders@...omium.org>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-snps-arc@...ts.infradead.org,
        Stable <stable@...r.kernel.org>,
        Vineet Gupta <Vineet.Gupta1@...opsys.com>
Subject: Re: [PATCH 2/2 v3] mmc: dw_mmc: Fix the CTO overflow calculation for
 32-bit systems

On Mon, Feb 26, 2018 at 4:34 PM, Evgeniy Didin
<Evgeniy.Didin@...opsys.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() ?

-- 
With Best Regards,
Andy Shevchenko