pwm: meson: Use mul_u64_u64_div_u64() for frequency calculating

[ Upstream commit 32c44e1fa921aebf8a5ef9f778534a30aab39313 ]

While calculating frequency for the given period u64 numbers are
multiplied before division what can lead to overflow in theory so use
secure mul_u64_u64_div_u64() which handles overflow correctly.

Fixes: 329db102a26d ("pwm: meson: make full use of common clock framework")
Suggested-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: George Stark <gnstark@salutedevices.com>
Link: https://lore.kernel.org/r/20240425171253.2752877-4-gnstark@salutedevices.com
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/drivers/pwm/pwm-meson.c b/drivers/pwm/pwm-meson.c
index 6fefa80af0a4cd9c959c8d755eeb9787d8861f47..52ac3277f42047e434c58bbcf5f371e809f53cc6 100644 (file)
--- a/drivers/pwm/pwm-meson.c
+++ b/drivers/pwm/pwm-meson.c
@@ -177,7 +177,7 @@ static int meson_pwm_calc(struct pwm_chip *chip, struct pwm_device *pwm,
 
        dev_dbg(pwmchip_parent(chip), "fin_freq: %ld Hz\n", fin_freq);
 
-       cnt = div_u64(fin_freq * period, NSEC_PER_SEC);
+       cnt = mul_u64_u64_div_u64(fin_freq, period, NSEC_PER_SEC);
        if (cnt > 0xffff) {
                dev_err(pwmchip_parent(chip), "unable to get period cnt\n");
                return -EINVAL;
@@ -192,7 +192,7 @@ static int meson_pwm_calc(struct pwm_chip *chip, struct pwm_device *pwm,
                channel->hi = 0;
                channel->lo = cnt;
        } else {
-               duty_cnt = div_u64(fin_freq * duty, NSEC_PER_SEC);
+               duty_cnt = mul_u64_u64_div_u64(fin_freq, duty, NSEC_PER_SEC);
 
                dev_dbg(pwmchip_parent(chip), "duty=%llu duty_cnt=%u\n", duty, duty_cnt);