watchdog: dw_wdt: fix overflow issue in dw_wdt_top_in_seconds

If top is 15, (1 << (16 + top)) may be negative.

Change-Id: I76e4a603a54f093e64a4b266008570e3afcdb35a
Signed-off-by: Huibin Hong <huibin.hong@rock-chips.com>

diff --git a/drivers/watchdog/dw_wdt.c b/drivers/watchdog/dw_wdt.c
index 6ea0634345e99512eefec4f82ebcd8ee348bac82..059c9746f5f7131a668a66f7dd6e8403a5e9b6cc 100644 (file)
--- a/drivers/watchdog/dw_wdt.c
+++ b/drivers/watchdog/dw_wdt.c
@@ -81,7 +81,9 @@ static inline int dw_wdt_top_in_seconds(unsigned top)
         * There are 16 possible timeout values in 0..15 where the number of
         * cycles is 2 ^ (16 + i) and the watchdog counts down.
         */
-       return (1 << (16 + top)) / clk_get_rate(dw_wdt.clk);
+       unsigned int cycles = 1 << (16 + top);
+
+       return cycles / clk_get_rate(dw_wdt.clk);
 }
 
 static int dw_wdt_get_top(void)