Re: [igt-dev] [PATCH i-g-t 01/17] tests/kms_dither: New IGT to validate crtc Dithering

From: Bhanuprakash Modem <redacted>

Many of the display devices have color format support less than the color format of
the input data (Ex: 8-bit input data and 6-bit display color depth). Then the input data
will be either truncated or rounded, but this approach usually causes loss of detail
and also produce large banded areas of a single color that significantly differs from
the original image.

Dithering is a technique used to enhance these colors by creating the illusion of
smoothness by adjusting the nearby pixel color.
For Eg: Converting 8-bit to 6-bit by modifying the pixel information.

Dithering should be enabled when a panel color depth is lower than the color depth
of the framebuffer.

Even though feature Dithering is there since legacy, there is no specific IGT for this.
This patch will create New IGT for Dithering.
And below is the truth table for CRTC Dithering.

|----------------|---------|-------------|
|  Frame buffer  |  Panel  |  Dithering  |
|----------------|---------|-------------|
|      8 BPC     |  6 BPC  |     Yes     |
|----------------|---------|-------------|
|      8 BPC     |  8 BPC  |     No      |
|----------------|---------|-------------|
|      8 BPC     | 10 BPC  |     No      |
|----------------|---------|-------------|
|     10 BPC     |  6 BPC  |     Yes     |
|----------------|---------|-------------|
|     10 BPC     |  8 BPC  |     Yes     |
|----------------|---------|-------------|
|     10 BPC     | 10 BPC  |     No      |
|----------------|---------|-------------|
|     16 BPC     |  6 BPC  |     Yes     |
|----------------|---------|-------------|
|     16 BPC     |  8 BPC  |     Yes     |
|----------------|---------|-------------|
|     16 BPC     | 10 BPC  |     Yes     |
|----------------|---------|-------------|

Cc: Swati Sharma <redacted>
Cc: Karthik B S <redacted>
Cc: Uma Shankar <redacted>
Cc: Nischal Varide <redacted>
Cc: Petri Latvala <redacted>
Signed-off-by: Bhanuprakash Modem <redacted>
---
 tests/kms_dither.c | 250 +++++++++++++++++++++++++++++++++++++++++++++
 tests/meson.build  |   1 +
 2 files changed, 251 insertions(+)
 create mode 100644 tests/kms_dither.c

diff --git a/tests/kms_dither.c b/tests/kms_dither.c new file mode 100644 index

0000000000..c25d623f81

--- /dev/null
+++ b/tests/kms_dither.c

@@ -0,0 +1,250 @@
+/*
+ * Copyright © 2020 Intel Corporation
+ *
+ * Permission is hereby granted, free of charge, to any person
+obtaining a
+ * copy of this software and associated documentation files (the
+"Software"),
+ * to deal in the Software without restriction, including without
+limitation
+ * the rights to use, copy, modify, merge, publish, distribute,
+sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom
+the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the
+next
+ * paragraph) shall be included in all copies or substantial portions
+of the
+ * Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT
+SHALL
+ * THE COPYRIGHT HOLDER(S) OR AUTHOR(S) BE LIABLE FOR ANY CLAIM,
+DAMAGES OR
+ * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
+OTHERWISE,
+ * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE
+OR
+ * OTHER DEALINGS IN THE SOFTWARE.
+ *
+ * Authors:
+ *     Bhanuprakash Modem <bhanuprakash.modem@intel.com>
+ *
+ */
+
+#include "igt.h"
+#include <fcntl.h>
+#include <termios.h>
+#include <unistd.h>
+
+IGT_TEST_DESCRIPTION("Test Dithering block status");
+
+/* Connector BPC */
+#define IGT_CONNECTOR_BPC_6		6
+#define IGT_CONNECTOR_BPC_8		8
+#define IGT_CONNECTOR_BPC_10		10
+#define IGT_CONNECTOR_BPC_12		12
+
+/* Framebuffer BPC */
+#define IGT_FRAME_BUFFER_BPC_8		8
+#define IGT_FRAME_BUFFER_BPC_10		10
+#define IGT_FRAME_BUFFER_BPC_16		16
+
+/* Common test data. */
+typedef struct data {
+	igt_display_t display;
+	igt_plane_t *primary;
+	igt_output_t *output;
+	igt_pipe_t *pipe;
+	drmModeModeInfo *mode;
+	enum pipe pipe_id;
+	int drm_fd;
+	igt_fb_t fb;
+} data_t;
+
+typedef struct {
+	unsigned int bpc;
+	unsigned int dither;
+} dither_status_t;
+
+/* Prepare test data. */
+static void prepare_test(data_t *data, igt_output_t *output, enum pipe
+pipe) {
+	igt_display_t *display = &data->display;
+
+	data->pipe_id = pipe;
+	data->pipe = &data->display.pipes[data->pipe_id];
+	igt_assert(data->pipe);
+
+	igt_display_reset(display);
+
+	data->output = output;
+	igt_assert(data->output);
+
+	data->mode = igt_output_get_mode(data->output);
+	igt_assert(data->mode);
+
+	data->primary =
+		igt_pipe_get_plane_type(data->pipe,

DRM_PLANE_TYPE_PRIMARY);
+
+	igt_output_set_pipe(data->output, data->pipe_id); }
+
+/* Returns the current state of dithering from the crtc debugfs. */
+static dither_status_t get_dither_state(data_t *data) {
+	char buf[256];
+	char crtc_name[7];
+	char *start_loc;
+	int fd, res;
+	dither_status_t status;
+
+	snprintf(crtc_name, 7, "crtc-%d", data->pipe_id);
+	fd = igt_debugfs_open(data->drm_fd, crtc_name, O_RDONLY);
+	igt_assert(fd >= 0);
+
+	res = igt_debugfs_simple_read(fd, "dither", buf, sizeof(buf));
+	igt_require(res > 0);
+	close(fd);
+
+	igt_assert(start_loc = strstr(buf, "bpc: "));
+	igt_assert_eq(sscanf(start_loc, "bpc: %u", &status.bpc), 1);
+
+	igt_assert(start_loc = strstr(buf, "Dither: "));
+	igt_assert_eq(sscanf(start_loc, "Dither: %u", &status.dither), 1);
+
+	return status;
+}
+
+static void test_dithering(data_t *data, enum pipe pipe,
+			   igt_output_t *output,
+			   int fb_bpc, int fb_format,
+			   int output_bpc)
+{
+	igt_display_t *display = &data->display;
+	dither_status_t status;
+	int bpc;
+
+	igt_info("Dithering test execution on %s PIPE_%s\n",
+			output->name, kmstest_pipe_name(pipe));
+	prepare_test(data, output, pipe);
+
+	igt_assert(igt_create_fb(data->drm_fd, data->mode->hdisplay,
+				 data->mode->vdisplay, fb_format,
+				 LOCAL_DRM_FORMAT_MOD_NONE, &data->fb));
+	igt_plane_set_fb(data->primary, &data->fb);
+	igt_plane_set_size(data->primary, data->mode->hdisplay,
+data->mode->vdisplay);
+
+	bpc = igt_output_get_prop(output, IGT_CONNECTOR_MAX_BPC);
+	igt_output_set_prop_value(data->output, IGT_CONNECTOR_MAX_BPC,
output_bpc);
+	igt_display_commit2(display, display->is_atomic ? COMMIT_ATOMIC :
+COMMIT_LEGACY);
+
+	/*
+	 * Check the status of Dithering block:
+	 *
+	 * Preserve the result & compute later (after clean-up).
+	 * If fb_bpc is greater than output_bpc, Dithering should be enabled
+	 * Else disabled
+	 */
+	status = get_dither_state(data);
+
+	igt_debug("FB BPC:%d, Panel BPC:%d, Pipe BPC:%d, Expected Dither:%s,
Actual result:%s\n",
+		  fb_bpc, output_bpc, status.bpc,
+		  (fb_bpc > output_bpc) ? "Enable": "Disable",
+		  status.dither ? "Enable": "Disable");
+
+       /*
+	* We must update the Connector max_bpc property back
+	* Otherwise, previously updated value will stay forever and
+	* may cause the failures for next/other subtests.
+	*/
+	igt_output_set_prop_value(data->output, IGT_CONNECTOR_MAX_BPC,
bpc);
+	igt_plane_set_fb(data->primary, NULL);
+	igt_output_set_pipe(output, PIPE_NONE);
+	igt_display_commit2(display, display->is_atomic ? COMMIT_ATOMIC :
COMMIT_LEGACY);
+	igt_remove_fb(data->drm_fd, &data->fb);
+
+	/* Check if crtc bpc is updated with requested one. */
+	igt_require_f((status.bpc == output_bpc),
+			"%s can support max %u-bpc, but requested %d-bpc\n",
+				output->name, status.bpc, output_bpc);
+
+	/* Compute the result. */
+	if (fb_bpc > output_bpc)
+		igt_assert_f(status.dither, "(fb_%dbpc > output_%dbpc): Dither
should be enabled\n",
+				fb_bpc, output_bpc);
+	else
+		igt_assert_f(!status.dither, "(fb_%dbpc <= output_%dbpc): Dither
should be disabled\n",
+				fb_bpc, output_bpc);
+
+	return;
+}
+
+/* Returns true if an output supports max bpc property & max_bpc >=
+requested. */ static bool is_supported(igt_output_t *output, int bpc) {
+        return igt_output_has_prop(output, IGT_CONNECTOR_MAX_BPC) &&
+		(igt_output_get_prop(output, IGT_CONNECTOR_MAX_BPC) >= bpc);
}
+
+static void
+run_dither_test(data_t *data, int fb_bpc, int fb_format, int
+output_bpc) {
+	igt_output_t *output;
+	igt_display_t *display = &data->display;
+
+	for_each_connected_output(display, output) {
+		enum pipe pipe;
+
+		if (!is_supported(output, output_bpc))
+			continue;
+
+		if ((strstr(output->name, "HDMI") != NULL) &&
+		    (output_bpc == IGT_CONNECTOR_BPC_6))
+			continue;
+
+		for_each_pipe(display, pipe) {
+			if (igt_pipe_connector_valid(pipe, output)) {
+				igt_dynamic_f("%s-pipe-%s", output->name,
kmstest_pipe_name(pipe))
+					test_dithering(data, pipe, output, fb_bpc,
+							fb_format, output_bpc);
+
+				/* One pipe is enough */
+				break;
+			}
+		}
+	}
+}
+
+igt_main
+{
+	struct {
+		int fb_bpc;
+		int format;
+		int output_bpc;
+	} tests[] = {
+		{ IGT_FRAME_BUFFER_BPC_8, DRM_FORMAT_XRGB8888,
IGT_CONNECTOR_BPC_6 },
+		{ IGT_FRAME_BUFFER_BPC_8, DRM_FORMAT_XRGB8888,
IGT_CONNECTOR_BPC_8 },
+	};
+	int i;
+	data_t data = { 0 };
+
+	igt_fixture {
+		data.drm_fd = drm_open_driver_master(DRIVER_INTEL);
+		kmstest_set_vt_graphics_mode();
+
+		igt_display_require(&data.display, data.drm_fd);
+		igt_display_require_output(&data.display);
+	}
+
+	for (i = 0; i < ARRAY_SIZE(tests); i++) {
+		igt_describe_f("Framebuffer BPC:%d, Panel BPC:%d, Expected
Dither:%s\n",
+			       tests[i].fb_bpc, tests[i].output_bpc,
+			       (tests[i].fb_bpc > tests[i].output_bpc) ?
+							"Enable": "Disable");
+
+		igt_subtest_with_dynamic_f("FB-%dBPC-Vs-Panel-%dBPC",
+				tests[i].fb_bpc, tests[i].output_bpc)
+			run_dither_test(&data,
+					tests[i].fb_bpc,
+					tests[i].format,
+					tests[i].output_bpc);
+	}
+
+	igt_fixture {
+		igt_display_fini(&data.display);
+	}
+}

diff --git a/tests/meson.build b/tests/meson.build index 2351b3d3fa..e5954e2832

100644

--- a/tests/meson.build
+++ b/tests/meson.build

@@ -28,6 +28,7 @@ test_progs = [
 	'kms_cursor_crc',
 	'kms_cursor_edge_walk',
 	'kms_cursor_legacy',
+	'kms_dither',
 	'kms_dp_aux_dev',
 	'kms_dp_dsc',
 	'kms_dp_tiled_display',
--

2.25.1