linux-kernel - [PATCH] net: dsa: ocelot: use div64_u64() instead of do

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Date:   Wed,  9 Feb 2022 00:39:02 -0800
From:   Qing Wang <wangqing@...o.com>
To:     Vladimir Oltean <vladimir.oltean@....com>,
        Claudiu Manoil <claudiu.manoil@....com>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        UNGLinuxDriver@...rochip.com, Andrew Lunn <andrew@...n.ch>,
        Vivien Didelot <vivien.didelot@...il.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc:     Wang Qing <wangqing@...o.com>
Subject: [PATCH] net: dsa: ocelot: use div64_u64() instead of do_div()

From: Wang Qing <wangqing@...o.com>

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@...o.com>
---
 drivers/net/dsa/ocelot/felix_vsc9959.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/dsa/ocelot/felix_vsc9959.c b/drivers/net/dsa/ocelot/felix_vsc9959.c
index bf8d382..5c2482f
--- a/drivers/net/dsa/ocelot/felix_vsc9959.c
+++ b/drivers/net/dsa/ocelot/felix_vsc9959.c
@@ -1178,7 +1178,7 @@ static void vsc9959_new_base_time(struct ocelot *ocelot, ktime_t base_time,
 	if (base_time < current_time) {
 		u64 nr_of_cycles = current_time - base_time;
 
-		do_div(nr_of_cycles, cycle_time);
+		div64_u64(nr_of_cycles, cycle_time);
 		new_base_time += cycle_time * (nr_of_cycles + 1);
 	}
 
-- 
2.7.4