Re: [PATCH] mmc: mtk-sd: use div64_u64() instead of do_div()

[Christophe JAILLET]

Le 17/02/2022 à 16:39, Ulf Hansson a écrit :
> On Wed, 9 Feb 2022 at 09:39, Qing Wang <wangqing@xxxxxxxx> wrote:
> > From: Wang Qing <wangqing@xxxxxxxx>
> >
> > do_div() does a 64-by-32 division.
> > When the divisor is u64, do_div() truncates it to 32 bits, this means it
> > can test non-zero and be truncated to zero for division.
> >
> > fix do_div.cocci warning:
> > do_div() does a 64-by-32 division, please consider using div64_u64 instead.
> >
> > Signed-off-by: Wang Qing <wangqing@xxxxxxxx>
>
> Applied for next, thanks!


This is wrong.

See [1].


Wang Qing, you should really warn all the people you have sent such patches.

CJ

[1]: 
https://lore.kernel.org/linux-kernel/19b96972-cee7-937f-21ce-c78982ed2048@xxxxxxxxxx/


> Kind regards
> Uffe
>
>
> > ---
> >   drivers/mmc/host/mtk-sd.c | 2 +-
> >   1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/mmc/host/mtk-sd.c b/drivers/mmc/host/mtk-sd.c
> > index 65037e1..777c9a8
> > --- a/drivers/mmc/host/mtk-sd.c
> > +++ b/drivers/mmc/host/mtk-sd.c
> > @@ -766,7 +766,7 @@ static u64 msdc_timeout_cal(struct msdc_host *host, u64 ns, u64 clks)
> >                  clk_ns  = 1000000000ULL;
> >                  do_div(clk_ns, mmc->actual_clock);
> >                  timeout = ns + clk_ns - 1;
> > -               do_div(timeout, clk_ns);
> > +               div64_u64(timeout, clk_ns);
> >                  timeout += clks;
> >                  /* in 1048576 sclk cycle unit */
> >                  timeout = DIV_ROUND_UP(timeout, BIT(20));
> > --
> > 2.7.4