From mboxrd@z Thu Jan 1 00:00:00 1970 From: Evgeniy.Didin@synopsys.com (Evgeniy Didin) Date: Mon, 26 Feb 2018 15:14:21 +0000 Subject: [PATCH 2/2 v3] mmc: dw_mmc: Fix the CTO overflow calculation for 32-bit systems In-Reply-To: References: <20180226143413.44134-1-Evgeniy.Didin@synopsys.com> <20180226143413.44134-3-Evgeniy.Didin@synopsys.com> List-ID: Message-ID: <1519658060.31245.4.camel@synopsys.com> To: linux-snps-arc@lists.infradead.org On Mon, 2018-02-26@16:39 +0200, Andy Shevchenko wrote: > On Mon, Feb 26, 2018 at 4:34 PM, Evgeniy Didin > 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