OMAP: DSS2: Reject scaling settings when they cannot be supported

If the scaling ratio is below 0.5 video output width can't be identical
to the display width. Reject such settings.

Signed-off-by: Ville Syrjälä <ville.syrjala@nokia.com>
Acked-by: Tomi Valkeinen <tomi.valkeinen@nokia.com>

drivers/video/omap2/dss/dispc.c

@@ -1454,7 +1454,10 @@ static unsigned long calc_fclk_five_taps(u16 width, u16 height,
 		do_div(tmp, 2 * out_height * ppl);
 		fclk = tmp;
 
-		if (height > 2 * out_height && ppl != out_width) {
+		if (height > 2 * out_height) {
+			if (ppl == out_width)
+				return 0;
+
 			tmp = pclk * (height - 2 * out_height) * out_width;
 			do_div(tmp, 2 * out_height * (ppl - out_width));
 			fclk = max(fclk, (u32) tmp);
@@ -1634,7 +1637,7 @@ static int _dispc_setup_plane(enum omap_plane plane,
 		DSSDBG("required fclk rate = %lu Hz\n", fclk);
 		DSSDBG("current fclk rate = %lu Hz\n", dispc_fclk_rate());
 
-		if (fclk > dispc_fclk_rate()) {
+		if (!fclk || fclk > dispc_fclk_rate()) {
 			DSSERR("failed to set up scaling, "
 					"required fclk rate = %lu Hz, "
 					"current fclk rate = %lu Hz\n",