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

[Andy Shevchenko]

On Mon, Feb 26, 2018 at 5:14 PM, Evgeniy Didin
<Evgeniy.Didin@xxxxxxxxxxxx> wrote:
> 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@xxxxxxxxxxxx> 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.

Did you try to compile your code for 32-bit target?

-- 
With Best Regards,
Andy Shevchenko