staging: fbtft: fb_ssd1331: fix mirrored display

When the row scan order is reversed (the default) we also need to
reverse the column scan order. This was not done previously, resulting
in a mirrored display.

Also add support for 180 degree display rotation, in which case simply
disable reversed row and column scan order.

Tested on an Adafruit 0.96" mini Color OLED display.
Signed-off-by: Johannes H. Jensen <joh@pseudoberries.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/fbtft/fb_ssd1331.c

@@ -26,7 +26,13 @@ static int init_display(struct fbtft_par *par)
 	par->fbtftops.reset(par);
 
 	write_reg(par, 0xae); /* Display Off */
-	write_reg(par, 0xa0, 0x70 | (par->bgr << 2)); /* Set Colour Depth */
+
+	/* Set Column Address Mapping, COM Scan Direction and Colour Depth */
+	if (par->info->var.rotate == 180)
+		write_reg(par, 0xa0, 0x60 | (par->bgr << 2));
+	else
+		write_reg(par, 0xa0, 0x72 | (par->bgr << 2));
+
 	write_reg(par, 0x72); /* RGB colour */
 	write_reg(par, 0xa1, 0x00); /* Set Display Start Line */
 	write_reg(par, 0xa2, 0x00); /* Set Display Offset */