linux-kernel - [PATCH -next v2] ethernet: renesas: Use div64_ul instead of do

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Message-Id: <1637228883-100100-1-git-send-email-yang.lee@linux.alibaba.com>
Date:   Thu, 18 Nov 2021 17:48:03 +0800
From:   Yang Li <yang.lee@...ux.alibaba.com>
To:     davem@...emloft.net
Cc:     kuba@...nel.org, s.shtylyov@....ru, geert@...ux-m68k.org,
        netdev@...r.kernel.org, linux-renesas-soc@...r.kernel.org,
        linux-kernel@...r.kernel.org, Yang Li <yang.lee@...ux.alibaba.com>
Subject: [PATCH -next v2] ethernet: renesas: Use div64_ul instead of do_div

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@...ux.alibaba.com>
Signed-off-by: Yang Li <yang.lee@...ux.alibaba.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@...der.be>
Reviewed-by: Sergey Shtylyov <s.shtylyov@....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