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

Commit Message

Yang Li Nov. 18, 2021, 9:48 a.m. UTC

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 <[e-mail]>
Signed-off-by: Yang Li <[e-mail]>
Reviewed-by: Geert Uytterhoeven <[e-mail]>
Reviewed-by: Sergey Shtylyov <[e-mail]>
---

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(-)

Comments

Sergey Shtylyov Nov. 18, 2021, 10:06 a.m. UTC | #1

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 <[e-mail]>
> Signed-off-by: Yang Li <[e-mail]>
> Reviewed-by: Geert Uytterhoeven <[e-mail]>
> Reviewed-by: Sergey Shtylyov <[e-mail]>

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

[...]

MBR, Sergey

[e-mail] Nov. 20, 2021, 4:30 a.m. UTC | #2

Hello:

This patch was applied to netdev/net-next.git (master)
by Jakub Kicinski <[e-mail]>:

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!

Patch

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",