OMAPDSS: DISPC: Update Fir Coefficients

The FIR coefficients present in kernel are being updated to new coefficients
consisting of 24 coefficient tables, with 12 each for 3 tap and 5 tap scenario,
which are chosen on the basis of DISPC up/downsampling filters M value. M is
the inverse of low pass cut off frequency of the sampling filter. For vertical
scaling 3 tap or 5 tap tables are used based on the clock rate and width of
the line buffer whereas in OMAP2 3 tap is always used. For horizontal scaling
however 5 tap tables are always used.

New coefficients and the corresponding logic have been tested on OMAP2, OMAP3
and OMAP4. Horizontal and vertical scaling worked fine except for some 3 tap
vs 5 tap issue during vertical upscaling and clock failing issues which is
acknowledged in the next patch. Vertical upscaling was found to perform better
under 5 taps. The 24 coefficient tables have been moved to another file
dispc_coefs.c for proper maintainance.

This code is written based on code written by Lajos Molnar <lajos@ti.com> in
Android Kernel for scaling. Lajos Molnar <lajos@ti.com> had fine tuned the FIR
coefficient selection process and reduced outliness and blockiness around
images when upscaling more than 2 times.

Signed-off-by: Chandrabhanu Mahapatra <cmahapatra@ti.com>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>

1 files changed, 19 insertions, 118 deletions

diff --git a/drivers/video/omap2/dss/dispc.c b/drivers/video/omap2/dss/dispc.c
index 4d68428..78e51d9 100644
--- a/drivers/video/omap2/dss/dispc.c
+++ b/drivers/video/omap2/dss/dispc.c
@@ -64,22 +64,6 @@ struct omap_dispc_isr_data {
 	u32			mask;
 };
 
-struct dispc_h_coef {
-	s8 hc4;
-	s8 hc3;
-	u8 hc2;
-	s8 hc1;
-	s8 hc0;
-};
-
-struct dispc_v_coef {
-	s8 vc22;
-	s8 vc2;
-	u8 vc1;
-	s8 vc0;
-	s8 vc00;
-};
-
 enum omap_burst_size {
 	BURST_SIZE_X2 = 0,
 	BURST_SIZE_X4 = 1,
@@ -561,105 +545,27 @@ static void dispc_ovl_write_firv2_reg(enum omap_plane plane, int reg, u32 value)
 	dispc_write_reg(DISPC_OVL_FIR_COEF_V2(plane, reg), value);
 }
 
-static void dispc_ovl_set_scale_coef(enum omap_plane plane, int hscaleup,
-				  int vscaleup, int five_taps,
-				  enum omap_color_component color_comp)
-{
-	/* Coefficients for horizontal up-sampling */
-	static const struct dispc_h_coef coef_hup[8] = {
-		{  0,   0, 128,   0,  0 },
-		{ -1,  13, 124,  -8,  0 },
-		{ -2,  30, 112, -11, -1 },
-		{ -5,  51,  95, -11, -2 },
-		{  0,  -9,  73,  73, -9 },
-		{ -2, -11,  95,  51, -5 },
-		{ -1, -11, 112,  30, -2 },
-		{  0,  -8, 124,  13, -1 },
-	};
-
-	/* Coefficients for vertical up-sampling */
-	static const struct dispc_v_coef coef_vup_3tap[8] = {
-		{ 0,  0, 128,  0, 0 },
-		{ 0,  3, 123,  2, 0 },
-		{ 0, 12, 111,  5, 0 },
-		{ 0, 32,  89,  7, 0 },
-		{ 0,  0,  64, 64, 0 },
-		{ 0,  7,  89, 32, 0 },
-		{ 0,  5, 111, 12, 0 },
-		{ 0,  2, 123,  3, 0 },
-	};
-
-	static const struct dispc_v_coef coef_vup_5tap[8] = {
-		{  0,   0, 128,   0,  0 },
-		{ -1,  13, 124,  -8,  0 },
-		{ -2,  30, 112, -11, -1 },
-		{ -5,  51,  95, -11, -2 },
-		{  0,  -9,  73,  73, -9 },
-		{ -2, -11,  95,  51, -5 },
-		{ -1, -11, 112,  30, -2 },
-		{  0,  -8, 124,  13, -1 },
-	};
-
-	/* Coefficients for horizontal down-sampling */
-	static const struct dispc_h_coef coef_hdown[8] = {
-		{   0, 36, 56, 36,  0 },
-		{   4, 40, 55, 31, -2 },
-		{   8, 44, 54, 27, -5 },
-		{  12, 48, 53, 22, -7 },
-		{  -9, 17, 52, 51, 17 },
-		{  -7, 22, 53, 48, 12 },
-		{  -5, 27, 54, 44,  8 },
-		{  -2, 31, 55, 40,  4 },
-	};
-
-	/* Coefficients for vertical down-sampling */
-	static const struct dispc_v_coef coef_vdown_3tap[8] = {
-		{ 0, 36, 56, 36, 0 },
-		{ 0, 40, 57, 31, 0 },
-		{ 0, 45, 56, 27, 0 },
-		{ 0, 50, 55, 23, 0 },
-		{ 0, 18, 55, 55, 0 },
-		{ 0, 23, 55, 50, 0 },
-		{ 0, 27, 56, 45, 0 },
-		{ 0, 31, 57, 40, 0 },
-	};
-
-	static const struct dispc_v_coef coef_vdown_5tap[8] = {
-		{   0, 36, 56, 36,  0 },
-		{   4, 40, 55, 31, -2 },
-		{   8, 44, 54, 27, -5 },
-		{  12, 48, 53, 22, -7 },
-		{  -9, 17, 52, 51, 17 },
-		{  -7, 22, 53, 48, 12 },
-		{  -5, 27, 54, 44,  8 },
-		{  -2, 31, 55, 40,  4 },
-	};
-
-	const struct dispc_h_coef *h_coef;
-	const struct dispc_v_coef *v_coef;
+static void dispc_ovl_set_scale_coef(enum omap_plane plane, int fir_hinc,
+				int fir_vinc, int five_taps,
+				enum omap_color_component color_comp)
+{
+	const struct dispc_coef *h_coef, *v_coef;
 	int i;
 
-	if (hscaleup)
-		h_coef = coef_hup;
-	else
-		h_coef = coef_hdown;
-
-	if (vscaleup)
-		v_coef = five_taps ? coef_vup_5tap : coef_vup_3tap;
-	else
-		v_coef = five_taps ? coef_vdown_5tap : coef_vdown_3tap;
+	h_coef = dispc_ovl_get_scale_coef(fir_hinc, true);
+	v_coef = dispc_ovl_get_scale_coef(fir_vinc, five_taps);
 
 	for (i = 0; i < 8; i++) {
 		u32 h, hv;
 
-		h = FLD_VAL(h_coef[i].hc0, 7, 0)
-			| FLD_VAL(h_coef[i].hc1, 15, 8)
-			| FLD_VAL(h_coef[i].hc2, 23, 16)
-			| FLD_VAL(h_coef[i].hc3, 31, 24);
-		hv = FLD_VAL(h_coef[i].hc4, 7, 0)
-			| FLD_VAL(v_coef[i].vc0, 15, 8)
-			| FLD_VAL(v_coef[i].vc1, 23, 16)
-			| FLD_VAL(v_coef[i].vc2, 31, 24);
+		h = FLD_VAL(h_coef[i].hc0_vc00, 7, 0)
+			| FLD_VAL(h_coef[i].hc1_vc0, 15, 8)
+			| FLD_VAL(h_coef[i].hc2_vc1, 23, 16)
+			| FLD_VAL(h_coef[i].hc3_vc2, 31, 24);
+		hv = FLD_VAL(h_coef[i].hc4_vc22, 7, 0)
+			| FLD_VAL(v_coef[i].hc1_vc0, 15, 8)
+			| FLD_VAL(v_coef[i].hc2_vc1, 23, 16)
+			| FLD_VAL(v_coef[i].hc3_vc2, 31, 24);
 
 		if (color_comp == DISPC_COLOR_COMPONENT_RGB_Y) {
 			dispc_ovl_write_firh_reg(plane, i, h);
@@ -674,8 +580,8 @@ static void dispc_ovl_set_scale_coef(enum omap_plane plane, int hscaleup,
 	if (five_taps) {
 		for (i = 0; i < 8; i++) {
 			u32 v;
-			v = FLD_VAL(v_coef[i].vc00, 7, 0)
-				| FLD_VAL(v_coef[i].vc22, 15, 8);
+			v = FLD_VAL(v_coef[i].hc0_vc00, 7, 0)
+				| FLD_VAL(v_coef[i].hc4_vc22, 15, 8);
 			if (color_comp == DISPC_COLOR_COMPONENT_RGB_Y)
 				dispc_ovl_write_firv_reg(plane, i, v);
 			else
@@ -1228,17 +1134,12 @@ static void dispc_ovl_set_scale_param(enum omap_plane plane,
 		enum omap_color_component color_comp)
 {
 	int fir_hinc, fir_vinc;
-	int hscaleup, vscaleup;
-
-	hscaleup = orig_width <= out_width;
-	vscaleup = orig_height <= out_height;
-
-	dispc_ovl_set_scale_coef(plane, hscaleup, vscaleup, five_taps,
-			color_comp);
 
 	fir_hinc = 1024 * orig_width / out_width;
 	fir_vinc = 1024 * orig_height / out_height;
 
+	dispc_ovl_set_scale_coef(plane, fir_hinc, fir_vinc, five_taps,
+				color_comp);
 	dispc_ovl_set_fir(plane, fir_hinc, fir_vinc, color_comp);
 }