| Message ID | 1637203805-125780-1-git-send-email-yang.lee@linux.alibaba.com (mailing list archive) |
|---|---|
| State | Superseded |
| Delegated to: | Geert Uytterhoeven |
| Headers | show |
| Series | [-next] ethernet: renesas: Use div64_ul instead of do_div | expand |
Hello!
Why you didn't Cc me (as a reviewer)?
On 18.11.2021 5:50, Yang Li wrote:
> do_div() does a 64-by-32 division. Here the divisor is an
> unsigned long which on some platforms is 64 bit wide. So use
> div64_ul instead of do_div to avoid a possible truncation.
>
> Eliminate the following coccicheck warning:
> ./drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c:2742:1-7: WARNING:
> do_div() does a 64-by-32 division, please consider using div64_ul
> instead.
>
> Reported-by: Abaci Robot <abaci@linux.alibaba.com>
> Signed-off-by: Yang Li <yang.lee@linux.alibaba.com>
> ---
> drivers/net/ethernet/renesas/ravb_main.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/net/ethernet/renesas/ravb_main.c b/drivers/net/ethernet/renesas/ravb_main.c
> index b4c597f..2b89710 100644
> --- a/drivers/net/ethernet/renesas/ravb_main.c
> +++ b/drivers/net/ethernet/renesas/ravb_main.c
> @@ -2489,7 +2489,7 @@ static int ravb_set_gti(struct net_device *ndev)
> return -EINVAL;
>
> inc = 1000000000ULL << 20;
> - do_div(inc, rate);
> + inc = div64_ul(inc, rate);
Why not just:
inc = div64_ul(1000000000ULL << 20, rate);
> if (inc < GTI_TIV_MIN || inc > GTI_TIV_MAX) {
> dev_err(dev, "gti.tiv increment 0x%llx is outside the range 0x%x - 0x%x\n",
MBR, Sergey
From: Sergey Shtylyov > Sent: 18 November 2021 09:08 > On 18.11.2021 5:50, Yang Li wrote: > > > do_div() does a 64-by-32 division. Here the divisor is an > > unsigned long which on some platforms is 64 bit wide. So use > > div64_ul instead of do_div to avoid a possible truncation. > > > > Eliminate the following coccicheck warning: > > ./drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c:2742:1-7: WARNING: > > do_div() does a 64-by-32 division, please consider using div64_ul > > instead. > > > > Reported-by: Abaci Robot <abaci@linux.alibaba.com> > > Signed-off-by: Yang Li <yang.lee@linux.alibaba.com> > > --- > > drivers/net/ethernet/renesas/ravb_main.c | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/drivers/net/ethernet/renesas/ravb_main.c b/drivers/net/ethernet/renesas/ravb_main.c > > index b4c597f..2b89710 100644 > > --- a/drivers/net/ethernet/renesas/ravb_main.c > > +++ b/drivers/net/ethernet/renesas/ravb_main.c > > @@ -2489,7 +2489,7 @@ static int ravb_set_gti(struct net_device *ndev) > > return -EINVAL; > > > > inc = 1000000000ULL << 20; > > - do_div(inc, rate); > > + inc = div64_ul(inc, rate); > > Why not just: > > inc = div64_ul(1000000000ULL << 20, rate); > > > if (inc < GTI_TIV_MIN || inc > GTI_TIV_MAX) { > > dev_err(dev, "gti.tiv increment 0x%llx is outside the range 0x%x - 0x%x\n", Even with hardware divide a 64/32 divide is likely to be faster that a 64/64 one. Maybe the coccicheck warning message should suggest checking the domain of the divisor and then changing the type?? David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)
diff --git a/drivers/net/ethernet/renesas/ravb_main.c b/drivers/net/ethernet/renesas/ravb_main.c index b4c597f..2b89710 100644 --- a/drivers/net/ethernet/renesas/ravb_main.c +++ b/drivers/net/ethernet/renesas/ravb_main.c @@ -2489,7 +2489,7 @@ static int ravb_set_gti(struct net_device *ndev) return -EINVAL; inc = 1000000000ULL << 20; - do_div(inc, rate); + inc = div64_ul(inc, rate); if (inc < GTI_TIV_MIN || inc > GTI_TIV_MAX) { dev_err(dev, "gti.tiv increment 0x%llx is outside the range 0x%x - 0x%x\n",
do_div() does a 64-by-32 division. Here the divisor is an unsigned long which on some platforms is 64 bit wide. So use div64_ul instead of do_div to avoid a possible truncation. Eliminate the following coccicheck warning: ./drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c:2742:1-7: WARNING: do_div() does a 64-by-32 division, please consider using div64_ul instead. Reported-by: Abaci Robot <abaci@linux.alibaba.com> Signed-off-by: Yang Li <yang.lee@linux.alibaba.com> --- drivers/net/ethernet/renesas/ravb_main.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)