diff --git a/drivers/pwm/pwm-mtk-disp.c b/drivers/pwm/pwm-mtk-disp.c
index b5409e15dac8..56d10cde5b46 100644
--- a/drivers/pwm/pwm-mtk-disp.c
+++ b/drivers/pwm/pwm-mtk-disp.c
@@ -210,9 +210,9 @@ static int mtk_disp_pwm_get_state(struct pwm_chip *chip,
 	period = FIELD_GET(PWM_PERIOD_MASK, con1);
 	/*
 	 * period has 12 bits, clk_div 11 and NSEC_PER_SEC has 30,
-	 * so period * (clk_div + 1) * NSEC_PER_SEC doesn't overflow.
+	 * so (period + 1) * (clk_div + 1) * NSEC_PER_SEC doesn't overflow.
 	 */
-	state->period = DIV64_U64_ROUND_UP(period * (clk_div + 1) * NSEC_PER_SEC, rate);
+	state->period = DIV64_U64_ROUND_UP((period + 1) * (clk_div + 1) * NSEC_PER_SEC, rate);
 	high_width = FIELD_GET(PWM_HIGH_WIDTH_MASK, con1);
 	state->duty_cycle = DIV64_U64_ROUND_UP(high_width * (clk_div + 1) * NSEC_PER_SEC,
 					       rate);