Messages in this thread | | | From | Evgeniy Didin <> | 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 |
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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 | |