pwm: meson: Add check for error from clk_round_rate()

clk_round_rate() can return not only zero if requested frequency can not
be provided but also negative error code so add check for it too.

Also change type of variable holding clk_round_rate() result from
unsigned long to long. It's safe due to clk_round_rate() returns long.

Fixes: 329db10 ("pwm: meson: make full use of common clock framework")
Signed-off-by: Dmitry Rokosov <ddrokosov@salutedevices.com>
Signed-off-by: George Stark <gnstark@salutedevices.com>
Link: https://lore.kernel.org/r/20240425171253.2752877-3-gnstark@salutedevices.com
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>

Author: geo-stark

drivers/pwm/pwm-meson.c

@@ -148,7 +148,7 @@ static int meson_pwm_calc(struct pwm_chip *chip, struct pwm_device *pwm,
 	struct meson_pwm *meson = to_meson_pwm(chip);
 	struct meson_pwm_channel *channel = &meson->channels[pwm->hwpwm];
 	unsigned int cnt, duty_cnt;
-	unsigned long fin_freq;
+	long fin_freq;
 	u64 duty, period, freq;
 
 	duty = state->duty_cycle;
@@ -168,12 +168,13 @@ static int meson_pwm_calc(struct pwm_chip *chip, struct pwm_device *pwm,
 		freq = ULONG_MAX;
 
 	fin_freq = clk_round_rate(channel->clk, freq);
-	if (fin_freq == 0) {
-		dev_err(pwmchip_parent(chip), "invalid source clock frequency\n");
-		return -EINVAL;
+	if (fin_freq <= 0) {
+		dev_err(pwmchip_parent(chip),
+			"invalid source clock frequency %llu\n", freq);
+		return fin_freq ? fin_freq : -EINVAL;
 	}
 
-	dev_dbg(pwmchip_parent(chip), "fin_freq: %lu Hz\n", fin_freq);
+	dev_dbg(pwmchip_parent(chip), "fin_freq: %ld Hz\n", fin_freq);
 
 	cnt = div_u64(fin_freq * period, NSEC_PER_SEC);
 	if (cnt > 0xffff) {