leds: pwm-multicolor: Support active-low LEDs

Add support for LEDs wired up to light when the PWM output is low, just
like the regular PWM LEDs.
Signed-off-by: Emil Renner Berthing <emil.renner.berthing@canonical.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Pavel Machek <pavel@ucw.cz>

drivers/leds/rgb/leds-pwm-multicolor.c

@@ -19,6 +19,7 @@
 struct pwm_led {
 	struct pwm_device *pwm;
 	struct pwm_state state;
+	bool active_low;
 };
 
 struct pwm_mc_led {
@@ -45,6 +46,9 @@ static int led_pwm_mc_set(struct led_classdev *cdev,
 		duty *= mc_cdev->subled_info[i].brightness;
 		do_div(duty, cdev->max_brightness);
 
+		if (priv->leds[i].active_low)
+			duty = priv->leds[i].state.period - duty;
+
 		priv->leds[i].state.duty_cycle = duty;
 		priv->leds[i].state.enabled = duty > 0;
 		ret = pwm_apply_state(priv->leds[i].pwm,
@@ -76,6 +80,7 @@ static int iterate_subleds(struct device *dev, struct pwm_mc_led *priv,
 			goto release_fwnode;
 		}
 		pwm_init_state(pwmled->pwm, &pwmled->state);
+		pwmled->active_low = fwnode_property_read_bool(fwnode, "active-low");
 
 		ret = fwnode_property_read_u32(fwnode, "color", &color);
 		if (ret) {