pwm: mediatek: Implement .apply() callback

To eventually get rid of all legacy drivers convert this driver to the
modern world implementing .apply().
This just pushed a variant of pwm_apply_legacy() into the driver that was
slightly simplified because the driver doesn't provide a .set_polarity()
callback.
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>

drivers/pwm/pwm-mediatek.c

@@ -198,10 +198,33 @@ static void pwm_mediatek_disable(struct pwm_chip *chip, struct pwm_device *pwm)
 	pwm_mediatek_clk_disable(chip, pwm);
 }
 
+static int pwm_mediatek_apply(struct pwm_chip *chip, struct pwm_device *pwm,
+			      const struct pwm_state *state)
+{
+	int err;
+
+	if (state->polarity != PWM_POLARITY_NORMAL)
+		return -EINVAL;
+
+	if (!state->enabled) {
+		if (pwm->state.enabled)
+			pwm_mediatek_disable(chip, pwm);
+
+		return 0;
+	}
+
+	err = pwm_mediatek_config(pwm->chip, pwm, state->duty_cycle, state->period);
+	if (err)
+		return err;
+
+	if (!pwm->state.enabled)
+		err = pwm_mediatek_enable(chip, pwm);
+
+	return err;
+}
+
 static const struct pwm_ops pwm_mediatek_ops = {
-	.config = pwm_mediatek_config,
-	.enable = pwm_mediatek_enable,
-	.disable = pwm_mediatek_disable,
+	.apply = pwm_mediatek_apply,
 	.owner = THIS_MODULE,
 };