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OMAPDSS: DISPC: Update Fir Coefficients
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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>
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Chandrabhanu Mahapatra authored and Tomi Valkeinen committed Jan 2, 2012
1 parent 1f3f53a commit debd907
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Showing 4 changed files with 358 additions and 120 deletions.
4 changes: 2 additions & 2 deletions drivers/video/omap2/dss/Makefile
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Original file line number Diff line number Diff line change
@@ -1,6 +1,6 @@
obj-$(CONFIG_OMAP2_DSS) += omapdss.o
omapdss-y := core.o dss.o dss_features.o dispc.o display.o manager.o overlay.o \
apply.o
omapdss-y := core.o dss.o dss_features.o dispc.o dispc_coefs.o display.o \
manager.o overlay.o apply.o
omapdss-$(CONFIG_OMAP2_DSS_DPI) += dpi.o
omapdss-$(CONFIG_OMAP2_DSS_RFBI) += rfbi.o
omapdss-$(CONFIG_OMAP2_DSS_VENC) += venc.o
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137 changes: 19 additions & 118 deletions drivers/video/omap2/dss/dispc.c
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Original file line number Diff line number Diff line change
Expand Up @@ -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,
Expand Down Expand Up @@ -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);
Expand All @@ -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
Expand Down Expand Up @@ -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);
}

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11 changes: 11 additions & 0 deletions drivers/video/omap2/dss/dispc.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -97,6 +97,17 @@
#define DISPC_OVL_PRELOAD(n) (DISPC_OVL_BASE(n) + \
DISPC_PRELOAD_OFFSET(n))

/* DISPC up/downsampling FIR filter coefficient structure */
struct dispc_coef {
s8 hc4_vc22;
s8 hc3_vc2;
u8 hc2_vc1;
s8 hc1_vc0;
s8 hc0_vc00;
};

const struct dispc_coef *dispc_ovl_get_scale_coef(int inc, int five_taps);

/* DISPC manager/channel specific registers */
static inline u16 DISPC_DEFAULT_COLOR(enum omap_channel channel)
{
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