[PATCH] drm/imx/dcss: allow using nearest neighbor interpolation scaling

From: Laurentiu Palcu
Date: Thu Nov 05 2020 - 09:50:55 EST


This patch adds support for using NN interpolation scaling by setting the
SCALING_FILTER plane property to 1. Otherwise, the default method is used.

Signed-off-by: Laurentiu Palcu <laurentiu.palcu@xxxxxxxxxxx>
---
I had no retro pixel art games to test this with, so I used modetest to see the
results:

To test, I used a 240x135 buffer, upscaled 8 times to 1920x1080:
* default scaling method using gaussian filter:
/usr/bin/modetest -M imx-dcss -w 33:SCALING_FILTER:0 -P 33@38:240x135*8@XR24
* NN interpolation method:
/usr/bin/modetest -M imx-dcss -w 33:SCALING_FILTER:1 -P 33@38:240x135*8@XR24

Thanks,
laurentiu

drivers/gpu/drm/imx/dcss/dcss-dev.h | 3 ++
drivers/gpu/drm/imx/dcss/dcss-plane.c | 10 +++++-
drivers/gpu/drm/imx/dcss/dcss-scaler.c | 47 +++++++++++++++++++++-----
3 files changed, 50 insertions(+), 10 deletions(-)

diff --git a/drivers/gpu/drm/imx/dcss/dcss-dev.h b/drivers/gpu/drm/imx/dcss/dcss-dev.h
index c642ae17837f..1e582270c6ea 100644
--- a/drivers/gpu/drm/imx/dcss/dcss-dev.h
+++ b/drivers/gpu/drm/imx/dcss/dcss-dev.h
@@ -7,6 +7,7 @@
#define __DCSS_PRV_H__

#include <drm/drm_fourcc.h>
+#include <drm/drm_plane.h>
#include <linux/io.h>
#include <video/videomode.h>

@@ -165,6 +166,8 @@ void dcss_ss_sync_set(struct dcss_ss *ss, struct videomode *vm,
/* SCALER */
int dcss_scaler_init(struct dcss_dev *dcss, unsigned long scaler_base);
void dcss_scaler_exit(struct dcss_scaler *scl);
+void dcss_scaler_set_filter(struct dcss_scaler *scl, int ch_num,
+ enum drm_scaling_filter scaling_filter);
void dcss_scaler_setup(struct dcss_scaler *scl, int ch_num,
const struct drm_format_info *format,
int src_xres, int src_yres, int dst_xres, int dst_yres,
diff --git a/drivers/gpu/drm/imx/dcss/dcss-plane.c b/drivers/gpu/drm/imx/dcss/dcss-plane.c
index 5db093aada2f..03ba88f7f995 100644
--- a/drivers/gpu/drm/imx/dcss/dcss-plane.c
+++ b/drivers/gpu/drm/imx/dcss/dcss-plane.c
@@ -257,7 +257,8 @@ static bool dcss_plane_needs_setup(struct drm_plane_state *state,
state->src_h != old_state->src_h ||
fb->format->format != old_fb->format->format ||
fb->modifier != old_fb->modifier ||
- state->rotation != old_state->rotation;
+ state->rotation != old_state->rotation ||
+ state->scaling_filter != old_state->scaling_filter;
}

static void dcss_plane_atomic_update(struct drm_plane *plane,
@@ -313,6 +314,9 @@ static void dcss_plane_atomic_update(struct drm_plane *plane,
is_rotation_90_or_270 = state->rotation & (DRM_MODE_ROTATE_90 |
DRM_MODE_ROTATE_270);

+ dcss_scaler_set_filter(dcss->scaler, dcss_plane->ch_num,
+ state->scaling_filter);
+
dcss_scaler_setup(dcss->scaler, dcss_plane->ch_num,
state->fb->format,
is_rotation_90_or_270 ? src_h : src_w,
@@ -394,6 +398,10 @@ struct dcss_plane *dcss_plane_init(struct drm_device *drm,
if (ret)
return ERR_PTR(ret);

+ drm_plane_create_scaling_filter_property(&dcss_plane->base,
+ BIT(DRM_SCALING_FILTER_DEFAULT) |
+ BIT(DRM_SCALING_FILTER_NEAREST_NEIGHBOR));
+
drm_plane_create_rotation_property(&dcss_plane->base,
DRM_MODE_ROTATE_0,
DRM_MODE_ROTATE_0 |
diff --git a/drivers/gpu/drm/imx/dcss/dcss-scaler.c b/drivers/gpu/drm/imx/dcss/dcss-scaler.c
index cd21905de580..47852b9dd5ea 100644
--- a/drivers/gpu/drm/imx/dcss/dcss-scaler.c
+++ b/drivers/gpu/drm/imx/dcss/dcss-scaler.c
@@ -77,6 +77,8 @@ struct dcss_scaler_ch {

u32 c_vstart;
u32 c_hstart;
+
+ bool use_nn_interpolation;
};

struct dcss_scaler {
@@ -243,6 +245,17 @@ static void dcss_scaler_gaussian_filter(int fc_q, bool use_5_taps,
}
}

+static void dcss_scaler_nearest_neighbor_filter(bool use_5_taps,
+ int coef[][PSC_NUM_TAPS])
+{
+ int i, j;
+
+ for (i = 0; i < PSC_STORED_PHASES; i++)
+ for (j = 0; j < PSC_NUM_TAPS; j++)
+ coef[i][j] = j == PSC_NUM_TAPS >> 1 ?
+ (1 << PSC_COEFF_PRECISION) : 0;
+}
+
/**
* dcss_scaler_filter_design() - Compute filter coefficients using
* Gaussian filter.
@@ -253,7 +266,8 @@ static void dcss_scaler_gaussian_filter(int fc_q, bool use_5_taps,
*/
static void dcss_scaler_filter_design(int src_length, int dst_length,
bool use_5_taps, bool phase0_identity,
- int coef[][PSC_NUM_TAPS])
+ int coef[][PSC_NUM_TAPS],
+ bool nn_interpolation)
{
int fc_q;

@@ -263,8 +277,11 @@ static void dcss_scaler_filter_design(int src_length, int dst_length,
else
fc_q = div_q(dst_length, src_length * PSC_NUM_PHASES);

- /* compute gaussian filter coefficients */
- dcss_scaler_gaussian_filter(fc_q, use_5_taps, phase0_identity, coef);
+ if (nn_interpolation)
+ dcss_scaler_nearest_neighbor_filter(use_5_taps, coef);
+ else
+ /* compute gaussian filter coefficients */
+ dcss_scaler_gaussian_filter(fc_q, use_5_taps, phase0_identity, coef);
}

static void dcss_scaler_write(struct dcss_scaler_ch *ch, u32 val, u32 ofs)
@@ -653,12 +670,14 @@ static void dcss_scaler_yuv_coef_set(struct dcss_scaler_ch *ch,

/* horizontal luma */
dcss_scaler_filter_design(src_xres, dst_xres, false,
- src_xres == dst_xres, coef);
+ src_xres == dst_xres, coef,
+ ch->use_nn_interpolation);
dcss_scaler_program_7_coef_set(ch, DCSS_SCALER_COEF_HLUM, coef);

/* vertical luma */
dcss_scaler_filter_design(src_yres, dst_yres, program_5_taps,
- src_yres == dst_yres, coef);
+ src_yres == dst_yres, coef,
+ ch->use_nn_interpolation);

if (program_5_taps)
dcss_scaler_program_5_coef_set(ch, DCSS_SCALER_COEF_VLUM, coef);
@@ -678,14 +697,14 @@ static void dcss_scaler_yuv_coef_set(struct dcss_scaler_ch *ch,
/* horizontal chroma */
dcss_scaler_filter_design(src_xres, dst_xres, false,
(src_xres == dst_xres) && (ch->c_hstart == 0),
- coef);
+ coef, ch->use_nn_interpolation);

dcss_scaler_program_7_coef_set(ch, DCSS_SCALER_COEF_HCHR, coef);

/* vertical chroma */
dcss_scaler_filter_design(src_yres, dst_yres, program_5_taps,
(src_yres == dst_yres) && (ch->c_vstart == 0),
- coef);
+ coef, ch->use_nn_interpolation);
if (program_5_taps)
dcss_scaler_program_5_coef_set(ch, DCSS_SCALER_COEF_VCHR, coef);
else
@@ -700,12 +719,14 @@ static void dcss_scaler_rgb_coef_set(struct dcss_scaler_ch *ch,

/* horizontal RGB */
dcss_scaler_filter_design(src_xres, dst_xres, false,
- src_xres == dst_xres, coef);
+ src_xres == dst_xres, coef,
+ ch->use_nn_interpolation);
dcss_scaler_program_7_coef_set(ch, DCSS_SCALER_COEF_HLUM, coef);

/* vertical RGB */
dcss_scaler_filter_design(src_yres, dst_yres, false,
- src_yres == dst_yres, coef);
+ src_yres == dst_yres, coef,
+ ch->use_nn_interpolation);
dcss_scaler_program_7_coef_set(ch, DCSS_SCALER_COEF_VLUM, coef);
}

@@ -751,6 +772,14 @@ static void dcss_scaler_set_rgb10_order(struct dcss_scaler_ch *ch,
ch->sdata_ctrl |= a2r10g10b10_format << A2R10G10B10_FORMAT_POS;
}

+void dcss_scaler_set_filter(struct dcss_scaler *scl, int ch_num,
+ enum drm_scaling_filter scaling_filter)
+{
+ struct dcss_scaler_ch *ch = &scl->ch[ch_num];
+
+ ch->use_nn_interpolation = scaling_filter == DRM_SCALING_FILTER_NEAREST_NEIGHBOR;
+}
+
void dcss_scaler_setup(struct dcss_scaler *scl, int ch_num,
const struct drm_format_info *format,
int src_xres, int src_yres, int dst_xres, int dst_yres,
--
2.23.0