[PATCH -next v2] ethernet: renesas: Use div64_ul instead of do_div

[PATCH -next v2] ethernet: renesas: Use div64_ul instead of do_div

[Yang Li]

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/renesas/ravb_main.c:2492:1-7: 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>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Sergey Shtylyov <s.shtylyov@omp.ru>
---

change in v2:
--According to Geert's suggestion
  replace #include <asm/div64.h> by
  #include <linux/math64.h>
--According to Sergey's suggestion
  Merge two statements into one

 drivers/net/ethernet/renesas/ravb_main.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/drivers/net/ethernet/renesas/ravb_main.c b/drivers/net/ethernet/renesas/ravb_main.c
index b4c597f..151cce2 100644
--- a/drivers/net/ethernet/renesas/ravb_main.c
+++ b/drivers/net/ethernet/renesas/ravb_main.c
@@ -30,8 +30,7 @@
 #include <linux/spinlock.h>
 #include <linux/sys_soc.h>
 #include <linux/reset.h>
-
-#include <asm/div64.h>
+#include <linux/math64.h>
 
 #include "ravb.h"
 
@@ -2488,8 +2487,7 @@ static int ravb_set_gti(struct net_device *ndev)
 	if (!rate)
 		return -EINVAL;
 
-	inc = 1000000000ULL << 20;
-	do_div(inc, rate);
+	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",
-- 
1.8.3.1

Re: [PATCH -next v2] ethernet: renesas: Use div64_ul instead of do_div

[Sergey Shtylyov]

On 18.11.2021 12:48, 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/renesas/ravb_main.c:2492:1-7: 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>
> Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
> Reviewed-by: Sergey Shtylyov <s.shtylyov@omp.ru>

    I haven't given you this tag, yet I was going to give you one, so
it's OK finally. :-)

[...]

MBR, Sergey

Re: [PATCH -next v2] ethernet: renesas: Use div64_ul instead of do_div

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to netdev/net-next.git (master)
by Jakub Kicinski <kuba@kernel.org>:

On Thu, 18 Nov 2021 17:48:03 +0800 you 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/renesas/ravb_main.c:2492:1-7: WARNING:
> do_div() does a 64-by-32 division, please consider using div64_ul
> instead.
> 
> [...]

Here is the summary with links:
  - [-next,v2] ethernet: renesas: Use div64_ul instead of do_div
    https://git.kernel.org/netdev/net-next/c/d9f31aeaa1e5

You are awesome, thank you!
-- 
Deet-doot-dot, I am a bot.
https://korg.docs.kernel.org/patchwork/pwbot.html

Re: [PATCH -next v2] ethernet: renesas: Use div64_ul instead of do_div

[Geert Uytterhoeven]

Hi Yang,

On Thu, Nov 18, 2021 at 4:13 AM Yang Li <yang.lee@linux.alibaba.com> 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/renesas/ravb_main.c:2492:1-7: 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>

Thanks for your patch!

> --- 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",

Please also replace

    #include <asm/div64.h>

by

#include <linux/math64.h>

With that added:

Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds

[PATCH -next v2] ethernet: renesas: Use div64_ul instead of do_div

[Yang Li]

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/renesas/ravb_main.c:2492:1-7: 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>
---

change in v2:
--Fixed warning message

 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);
 
 	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",
-- 
1.8.3.1