clk: fixed-factor: round_rate should use do_div

clk->rate = parent->rate / div * mult

The formula is OK. But it may overflow while we do operate with
unsigned long. So use do_div instead.

Signed-off-by: Haojian Zhuang <haojian.zhuang@gmail.com>
Signed-off-by: Mike Turquette <mturquette@linaro.org>
[mturquette@linaro.org: improved $SUBJECT]

1 files changed, 4 insertions, 1 deletions

diff --git a/drivers/clk/clk-fixed-factor.c b/drivers/clk/clk-fixed-factor.c
index a4899855c0f6..1ef271e47594 100644
--- a/drivers/clk/clk-fixed-factor.c
+++ b/drivers/clk/clk-fixed-factor.c
@@ -28,8 +28,11 @@ static unsigned long clk_factor_recalc_rate(struct clk_hw *hw,
                 unsigned long parent_rate)
 {
         struct clk_fixed_factor *fix = to_clk_fixed_factor(hw);
+        unsigned long long int rate;
 
-        return parent_rate * fix->mult / fix->div;
+        rate = (unsigned long long int)parent_rate * fix->mult;
+        do_div(rate, fix->div);
+        return (unsigned long)rate;
 }
 
 static long clk_factor_round_rate(struct clk_hw *hw, unsigned long rate,