linux-kernel - Re: [PATCH] mmc: dw_mmc: Fix the DTO timeout overflow calculation for 32-bit systems

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Message-ID: <CAHp75VfyQz-W7DLJ4KvFRCPkOUnP3YQjSzn+Zsbx92Xb-x4GqA@mail.gmail.com>
Date:   Wed, 21 Feb 2018 21:16:26 +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>,
        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
Subject: Re: [PATCH] mmc: dw_mmc: Fix the DTO timeout overflow calculation for
 32-bit systems

On Wed, Feb 21, 2018 at 7:57 PM, Evgeniy Didin
<Evgeniy.Didin@...opsys.com> wrote:
> In commit 9d9491a7da2a ("mmc: dw_mmc: Fix the DTO timeout calculation") have been made
> changes which can cause multiply overflow for 32-bit systems. It was caught on arc/hsdk board
> when "drto_ms" should be 671, but it was 70 and that caused a flow of stack-traces just copying
> file from mmc.
>
> Lets cast this multiply to long long int which prevents overflow.
>
> Signed-off-by: Evgeniy Didin <Evgeniy.Didin@...opsys.com>
> CC: Alexey Brodkin <abrodkin@...opsys.com>
> CC: Douglas Anderson <dianders@...omium.org>
> CC: Ulf Hansson <ulf.hansson@...aro.org>
> CC: linux-kernel@...r.kernel.org
> CC: linux-snps-arc@...ts.infradead.org

> --- a/drivers/mmc/host/dw_mmc.c
> +++ b/drivers/mmc/host/dw_mmc.c
> @@ -1944,7 +1944,7 @@ static void dw_mci_set_drto(struct dw_mci *host)
>         drto_div = (mci_readl(host, CLKDIV) & 0xff) * 2;
>         if (drto_div == 0)
>                 drto_div = 1;
> -       drto_ms = DIV_ROUND_UP(MSEC_PER_SEC * drto_clks * drto_div,
> +       drto_ms = DIV_ROUND_UP((uint64_t)MSEC_PER_SEC * drto_clks * drto_div,
>                                host->bus_hz);

Does the driver use uint64_t elsewhere?
Or simple u64?

-- 
With Best Regards,
Andy Shevchenko