video: mxsfb: enable setting HSYNC negative polarity

HSYNC signal can now be flipped according to display_flags bitmaks by
writing its bitmask on vdctrl0 register.

Signed-off-by: Giulio Benetti <giulio.benetti@benettiengineering.com>
Reviewed-by: Anatolij Gustschin <agust@denx.de>
diff --git a/drivers/video/mxsfb.c b/drivers/video/mxsfb.c
index cdd6dfa..9912cf3 100644
--- a/drivers/video/mxsfb.c
+++ b/drivers/video/mxsfb.c
@@ -57,8 +57,10 @@
 			 struct display_timing *timings, int bpp)
 {
 	struct mxs_lcdif_regs *regs = (struct mxs_lcdif_regs *)MXS_LCDIF_BASE;
+	const enum display_flags flags = timings->flags;
 	uint32_t word_len = 0, bus_width = 0;
 	uint8_t valid_data = 0;
+	uint32_t vdctrl0;
 
 #if CONFIG_IS_ENABLED(CLK)
 	struct clk per_clk;
@@ -118,10 +120,14 @@
 	writel((timings->vactive.typ << LCDIF_TRANSFER_COUNT_V_COUNT_OFFSET) |
 		timings->hactive.typ, &regs->hw_lcdif_transfer_count);
 
-	writel(LCDIF_VDCTRL0_ENABLE_PRESENT | LCDIF_VDCTRL0_ENABLE_POL |
-		LCDIF_VDCTRL0_VSYNC_PERIOD_UNIT |
-		LCDIF_VDCTRL0_VSYNC_PULSE_WIDTH_UNIT |
-		timings->vsync_len.typ, &regs->hw_lcdif_vdctrl0);
+	vdctrl0 = LCDIF_VDCTRL0_ENABLE_PRESENT | LCDIF_VDCTRL0_ENABLE_POL |
+		  LCDIF_VDCTRL0_VSYNC_PERIOD_UNIT |
+		  LCDIF_VDCTRL0_VSYNC_PULSE_WIDTH_UNIT |
+		  timings->vsync_len.typ;
+
+	if(flags & DISPLAY_FLAGS_HSYNC_HIGH)
+		vdctrl0 |= LCDIF_VDCTRL0_HSYNC_POL;
+	writel(vdctrl0, &regs->hw_lcdif_vdctrl0);
 	writel(timings->vback_porch.typ + timings->vfront_porch.typ +
 		timings->vsync_len.typ + timings->vactive.typ,
 		&regs->hw_lcdif_vdctrl1);