sunxi: video: Make pwm polarity configurable

It turns out that there are some panels where the pwm input is not active low,
so make it configurable.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Acked-by: Ian Campbell <ijc@hellion.org.uk>

board/sunxi/Kconfig

@@ -319,6 +319,13 @@ config VIDEO_LCD_BL_PWM
 	Set the backlight pwm pin for the LCD panel. This takes a string in the
 	format understood by sunxi_name_to_gpio, e.g. PH1 for pin 1 of port H.
 
+config VIDEO_LCD_BL_PWM_ACTIVE_LOW
+	bool "LCD panel backlight pwm is inverted"
+	depends on VIDEO
+	default y
+	---help---
+	Set this if the backlight pwm output is active low.
+
 
 # Note only one of these may be selected at a time! But hidden choices are
 # not supported by Kconfig

drivers/video/sunxi_display.c

@@ -23,6 +23,14 @@
 #include "hitachi_tx18d42vm_lcd.h"
 #include "ssd2828.h"
 
+#ifdef CONFIG_VIDEO_LCD_BL_PWM_ACTIVE_LOW
+#define PWM_ON 0
+#define PWM_OFF 1
+#else
+#define PWM_ON 1
+#define PWM_OFF 0
+#endif
+
 DECLARE_GLOBAL_DATA_PTR;
 
 enum sunxi_monitor {
@@ -598,8 +606,7 @@ static void sunxi_lcdc_panel_enable(void)
 	pin = sunxi_name_to_gpio(CONFIG_VIDEO_LCD_BL_PWM);
 	if (pin != -1) {
 		gpio_request(pin, "lcd_backlight_pwm");
-		/* backlight pwm is inverted, set to 1 to disable backlight */
-		gpio_direction_output(pin, 1);
+		gpio_direction_output(pin, PWM_OFF);
 	}
 
 	/* Give the backlight some time to turn off and power up the panel. */
@@ -626,10 +633,8 @@ static void sunxi_lcdc_backlight_enable(void)
 		gpio_direction_output(pin, 1);
 
 	pin = sunxi_name_to_gpio(CONFIG_VIDEO_LCD_BL_PWM);
-	if (pin != -1) {
-		/* backlight pwm is inverted, set to 0 to enable backlight */
-		gpio_direction_output(pin, 0);
-	}
+	if (pin != -1)
+		gpio_direction_output(pin, PWM_ON);
 }
 
 static int sunxi_lcdc_get_clk_delay(const struct ctfb_res_modes *mode)