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clk: atlas7: fix integer overflow in dto rate calculation 

I cannot believe that I spend quite a lot time in finding this bug.
It seems a pitfall people tend to fall in.

In "int64 = int32 * int32", conversion from 32-bits to 64-bits comes
after the multiplication. So this statement may not work as expected.

Signed-off-by: Yibo Cai <yibo.cai@csr.com>
Signed-off-by: Barry Song <Baohua.Song@csr.com>
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
This commit is contained in:
Yibo Cai 2015-08-04 14:45:28 +00:00 committed by Michael Turquette
parent b1062298fe
commit 6132e89aef
1 changed files with 2 additions and 2 deletions
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4
drivers/clk/sirf/clk-atlas7.c
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@ -519,7 +519,7 @@ static unsigned long dto_clk_recalc_rate(struct clk_hw *hw,
static long dto_clk_round_rate(struct clk_hw *hw, unsigned long rate,
unsigned long *parent_rate)
{
u64 dividend = rate * (1 << 29);
u64 dividend = (u64)rate * (1 << 29);
do_div(dividend, *parent_rate);
dividend *= *parent_rate;
@ -531,7 +531,7 @@ static long dto_clk_round_rate(struct clk_hw *hw, unsigned long rate,
static int dto_clk_set_rate(struct clk_hw *hw, unsigned long rate,
unsigned long parent_rate)
{
u64 dividend = rate * (1 << 29);
u64 dividend = (u64)rate * (1 << 29);
struct clk_dto *clk = to_dtoclk(hw);
do_div(dividend, parent_rate);