[PATCH] pwm: ipq: prevent potential 32-bit integer overflow in hi_div calculation

[PATCH] pwm: ipq: prevent potential 32-bit integer overflow in hi_div calculation

[kr494167]

From: Surendra Singh Chouhan <kr494167@gmail.com>

In ipq_pwm_get_state(), hi_div was calculated as:
  hi_div = hi_dur * (pre_div + 1);

hi_dur and (pre_div + 1) are both unsigned int (32-bit) values.
Evaluating their multiplication using 32-bit arithmetic before assigning to
the 64-bit u64 hi_div variable can overflow 32-bit unsigned math.

While effective_div explicitly uses (u64)(pwm_div + 1) * (pre_div + 1) to
prevent overflow, hi_div was missing the (u64) cast.

Fix this by casting hi_dur to (u64) before multiplication, matching the
precision used for effective_div.

Fixes: c436e3e9c265 ("pwm: Driver for qualcomm ipq6018 pwm block")
Signed-off-by: Surendra Singh Chouhan <kr494167@gmail.com>
---
 drivers/pwm/pwm-ipq.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/pwm/pwm-ipq.c b/drivers/pwm/pwm-ipq.c
index c53373948136..e27ddc8e9fea 100644
--- a/drivers/pwm/pwm-ipq.c
+++ b/drivers/pwm/pwm-ipq.c
@@ -186,7 +186,7 @@ static int ipq_pwm_get_state(struct pwm_chip *chip, struct pwm_device *pwm,
 	state->period = DIV64_U64_ROUND_UP(effective_div * NSEC_PER_SEC,
 					   ipq_chip->clk_rate);
 
-	hi_div = hi_dur * (pre_div + 1);
+	hi_div = (u64)hi_dur * (pre_div + 1);
 	state->duty_cycle = DIV64_U64_ROUND_UP(hi_div * NSEC_PER_SEC,
 					       ipq_chip->clk_rate);
 
-- 
2.55.0