atmel_lcdfb: implement inverted contrast pwm

This patch introduces lcdc->lcdcon_pol_negative which set CONTRAST_CTR
 register to inverted polarity.
Signed-off-by: Andreas Bießmann <biessmann@corscience.de>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>

drivers/video/atmel_lcdfb.c

@@ -68,7 +68,7 @@ static void atmel_lcdfb_update_dma2d(struct atmel_lcdfb_info *sinfo,
 }
 #endif
 
-static const u32 contrast_ctr = ATMEL_LCDC_PS_DIV8
+static u32 contrast_ctr = ATMEL_LCDC_PS_DIV8
 		| ATMEL_LCDC_POL_POSITIVE
 		| ATMEL_LCDC_ENA_PWMENABLE;
 
@@ -163,6 +163,10 @@ static void exit_backlight(struct atmel_lcdfb_info *sinfo)
 
 static void init_contrast(struct atmel_lcdfb_info *sinfo)
 {
+	/* contrast pwm can be 'inverted' */
+	if (sinfo->lcdcon_pol_negative)
+			contrast_ctr &= ~(ATMEL_LCDC_POL_POSITIVE);
+
 	/* have some default contrast/backlight settings */
 	lcdc_writel(sinfo, ATMEL_LCDC_CONTRAST_CTR, contrast_ctr);
 	lcdc_writel(sinfo, ATMEL_LCDC_CONTRAST_VAL, ATMEL_LCDC_CVAL_DEFAULT);
@@ -816,6 +820,7 @@ static int __init atmel_lcdfb_probe(struct platform_device *pdev)
 		sinfo->guard_time = pdata_sinfo->guard_time;
 		sinfo->smem_len = pdata_sinfo->smem_len;
 		sinfo->lcdcon_is_backlight = pdata_sinfo->lcdcon_is_backlight;
+		sinfo->lcdcon_pol_negative = pdata_sinfo->lcdcon_pol_negative;
 		sinfo->lcd_wiring_mode = pdata_sinfo->lcd_wiring_mode;
 	} else {
 		dev_err(dev, "cannot get default configuration\n");

include/video/atmel_lcdc.h

@@ -52,6 +52,7 @@ struct atmel_lcdfb_info {
 	u8			bl_power;
 #endif
 	bool			lcdcon_is_backlight;
+	bool			lcdcon_pol_negative;
 	u8			saved_lcdcon;
 
 	u8			default_bpp;