ARM: dts: AM33XX: Add PWM backlight DT data to am335x-evm

PWM output from ecap0 uses as backlight source. Also adds low threshold
value to have a uniform divisions in brightness-levels scales.
Signed-off-by: Philip Avinash <avinashphilip@ti.com>
Reviewed-by: Thierry Reding <thierry.reding@avionic-design.de>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Benoit Cousson <benoit.cousson@linaro.org>

arch/arm/boot/dts/am335x-evm.dts

@@ -91,6 +91,12 @@ nandflash_pins_s0: nandflash_pins_s0 {
 				0x9c (PIN_OUTPUT | MUX_MODE0)		/* gpmc_be0n_cle.gpmc_be0n_cle */
 			>;
 		};
+
+		ecap0_pins: backlight_pins {
+			pinctrl-single,pins = <
+				0x164 0x0	/* eCAP0_in_PWM0_out.eCAP0_in_PWM0_out MODE0 */
+			>;
+		};
 	};
 
 	ocp {
@@ -163,6 +169,16 @@ elm: elm@48080000 {
 			status = "okay";
 		};
 
+		epwmss0: epwmss@48300000 {
+			status = "okay";
+
+			ecap0: ecap@48300100 {
+				status = "okay";
+				pinctrl-names = "default";
+				pinctrl-0 = <&ecap0_pins>;
+			};
+		};
+
 		gpmc: gpmc@50000000 {
 			status = "okay";
 			pinctrl-names = "default";
@@ -299,6 +315,13 @@ switch@10 {
 			gpio-key,wakeup;
 		};
 	};
+
+	backlight {
+		compatible = "pwm-backlight";
+		pwms = <&ecap0 0 50000 0>;
+		brightness-levels = <0 51 53 56 62 75 101 152 255>;
+		default-brightness-level = <8>;
+	};
 };
 
 #include "tps65910.dtsi"