[PATCH V8 02/43] drm/vkms: Add kunit tests for VKMS LUT handling

[Alex Hung <alex.hung@amd.com>]

From: Harry Wentland <harry.wentland@amd.com>

Debugging LUT math is much easier when we can unit test
it. Add kunit functionality to VKMS and add tests for
 - get_lut_index
 - lerp_u16

Reviewed-by: Louis Chauvet <louis.chauvet@bootlin.com>
Signed-off-by: Alex Hung <alex.hung@amd.com>
Signed-off-by: Harry Wentland <harry.wentland@amd.com>
Cc: Arthur Grillo <arthurgrillo@riseup.net>
---
v8:
 - Update config names (Louis Chauvet)

v7:
 - Fix checkpatch warnings and errors (Louis Chauvet)
  - Change SPDX-License-Identifier: GPL-2.0+ from /* */ to //
  - Fix checkpatch errors and warnings (new line at EOF, redundant spaces, and long lines)
  - Add static to const struct vkms_color_lut test_linear_lut
 - Add "MODULE_DESCRIPTION" (Jeff Johnson)


v6:
 - Eliminate need to include test as .c file (Louis Chauvet)

v5:
 - Bring back static for lerp_u16 and get_lut_index (Arthur)

v4:
 - Test the critical points of the lerp function (Pekka)

v3:
 - Use include way of testing static functions (Arthur)

 drivers/gpu/drm/vkms/Kconfig                 |  15 ++
 drivers/gpu/drm/vkms/Makefile                |   1 +
 drivers/gpu/drm/vkms/tests/.kunitconfig      |   4 +
 drivers/gpu/drm/vkms/tests/Makefile          |   3 +
 drivers/gpu/drm/vkms/tests/vkms_color_test.c | 172 +++++++++++++++++++
 drivers/gpu/drm/vkms/vkms_composer.c         |   8 +-
 drivers/gpu/drm/vkms/vkms_composer.h         |  13 ++
 7 files changed, 214 insertions(+), 2 deletions(-)
 create mode 100644 drivers/gpu/drm/vkms/tests/.kunitconfig
 create mode 100644 drivers/gpu/drm/vkms/tests/Makefile
 create mode 100644 drivers/gpu/drm/vkms/tests/vkms_color_test.c
 create mode 100644 drivers/gpu/drm/vkms/vkms_composer.h

diff --git a/drivers/gpu/drm/vkms/Kconfig b/drivers/gpu/drm/vkms/Kconfig
index 9def079f685b..3c02f928ffe6 100644
--- a/drivers/gpu/drm/vkms/Kconfig
+++ b/drivers/gpu/drm/vkms/Kconfig
@@ -14,3 +14,18 @@ config DRM_VKMS
 	  a VKMS.
 
 	  If M is selected the module will be called vkms.
+
+config DRM_VKMS_KUNIT_TEST
+	tristate "KUnit tests for VKMS" if !KUNIT_ALL_TESTS
+	depends on DRM_VKMS && KUNIT
+	default KUNIT_ALL_TESTS
+	help
+	  This builds unit tests for VKMS. This option is not useful for
+	  distributions or general kernels, but only for kernel
+	  developers working on VKMS.
+
+	  For more information on KUnit and unit tests in general,
+	  please refer to the KUnit documentation in
+	  Documentation/dev-tools/kunit/.
+
+	  If in doubt, say "N".
diff --git a/drivers/gpu/drm/vkms/Makefile b/drivers/gpu/drm/vkms/Makefile
index 1b28a6a32948..490b26d2e69d 100644
--- a/drivers/gpu/drm/vkms/Makefile
+++ b/drivers/gpu/drm/vkms/Makefile
@@ -9,3 +9,4 @@ vkms-y := \
 	vkms_writeback.o
 
 obj-$(CONFIG_DRM_VKMS) += vkms.o
+obj-$(CONFIG_DRM_VKMS_KUNIT_TEST) += tests/
diff --git a/drivers/gpu/drm/vkms/tests/.kunitconfig b/drivers/gpu/drm/vkms/tests/.kunitconfig
new file mode 100644
index 000000000000..6a2d87068edc
--- /dev/null
+++ b/drivers/gpu/drm/vkms/tests/.kunitconfig
@@ -0,0 +1,4 @@
+CONFIG_KUNIT=y
+CONFIG_DRM=y
+CONFIG_DRM_VKMS=y
+CONFIG_DRM_VKMS_KUNIT_TEST=y
diff --git a/drivers/gpu/drm/vkms/tests/Makefile b/drivers/gpu/drm/vkms/tests/Makefile
new file mode 100644
index 000000000000..de1af87cbb11
--- /dev/null
+++ b/drivers/gpu/drm/vkms/tests/Makefile
@@ -0,0 +1,3 @@
+# SPDX-License-Identifier: GPL-2.0-only
+
+obj-$(CONFIG_DRM_VKMS_KUNIT_TEST) += vkms_color_test.o
\ No newline at end of file
diff --git a/drivers/gpu/drm/vkms/tests/vkms_color_test.c b/drivers/gpu/drm/vkms/tests/vkms_color_test.c
new file mode 100644
index 000000000000..affca56cac7b
--- /dev/null
+++ b/drivers/gpu/drm/vkms/tests/vkms_color_test.c
@@ -0,0 +1,172 @@
+// SPDX-License-Identifier: GPL-2.0+
+
+#include <kunit/test.h>
+
+#include <drm/drm_fixed.h>
+#include <drm/drm_mode.h>
+#include "../vkms_drv.h"
+#include "../vkms_composer.h"
+
+#define TEST_LUT_SIZE 16
+
+MODULE_IMPORT_NS("EXPORTED_FOR_KUNIT_TESTING");
+
+static struct drm_color_lut test_linear_array[TEST_LUT_SIZE] = {
+	{ 0x0, 0x0, 0x0, 0 },
+	{ 0x1111, 0x1111, 0x1111, 0 },
+	{ 0x2222, 0x2222, 0x2222, 0 },
+	{ 0x3333, 0x3333, 0x3333, 0 },
+	{ 0x4444, 0x4444, 0x4444, 0 },
+	{ 0x5555, 0x5555, 0x5555, 0 },
+	{ 0x6666, 0x6666, 0x6666, 0 },
+	{ 0x7777, 0x7777, 0x7777, 0 },
+	{ 0x8888, 0x8888, 0x8888, 0 },
+	{ 0x9999, 0x9999, 0x9999, 0 },
+	{ 0xaaaa, 0xaaaa, 0xaaaa, 0 },
+	{ 0xbbbb, 0xbbbb, 0xbbbb, 0 },
+	{ 0xcccc, 0xcccc, 0xcccc, 0 },
+	{ 0xdddd, 0xdddd, 0xdddd, 0 },
+	{ 0xeeee, 0xeeee, 0xeeee, 0 },
+	{ 0xffff, 0xffff, 0xffff, 0 },
+};
+
+static const struct vkms_color_lut test_linear_lut = {
+	.base = test_linear_array,
+	.lut_length = TEST_LUT_SIZE,
+	.channel_value2index_ratio = 0xf000fll
+};
+
+
+static void vkms_color_test_get_lut_index(struct kunit *test)
+{
+	s64 lut_index;
+	int i;
+
+	lut_index = get_lut_index(&test_linear_lut, test_linear_array[0].red);
+	KUNIT_EXPECT_EQ(test, drm_fixp2int(lut_index), 0);
+
+	for (i = 0; i < TEST_LUT_SIZE; i++) {
+		lut_index = get_lut_index(&test_linear_lut, test_linear_array[i].red);
+		KUNIT_EXPECT_EQ(test, drm_fixp2int_ceil(lut_index), i);
+	}
+}
+
+static void vkms_color_test_lerp(struct kunit *test)
+{
+	/*** half-way round down ***/
+	s64 t = 0x80000000 - 1;
+
+	KUNIT_EXPECT_EQ(test, lerp_u16(0x0, 0x10, t), 0x8);
+
+	/* odd a */
+	KUNIT_EXPECT_EQ(test, lerp_u16(0x1, 0x10, t), 0x8);
+
+	/* odd b */
+	KUNIT_EXPECT_EQ(test, lerp_u16(0x1, 0xf, t), 0x8);
+
+	/* b = a */
+	KUNIT_EXPECT_EQ(test, lerp_u16(0x10, 0x10, t), 0x10);
+
+	/* b = a + 1 */
+	KUNIT_EXPECT_EQ(test, lerp_u16(0x10, 0x11, t), 0x10);
+
+	/*** half-way round up ***/
+	t = 0x80000000;
+	KUNIT_EXPECT_EQ(test, lerp_u16(0x0, 0x10, t), 0x8);
+
+	/* odd a */
+	KUNIT_EXPECT_EQ(test, lerp_u16(0x1, 0x10, t), 0x9);
+
+	/* odd b */
+	KUNIT_EXPECT_EQ(test, lerp_u16(0x1, 0xf, t), 0x8);
+
+	/* b = a */
+	KUNIT_EXPECT_EQ(test, lerp_u16(0x10, 0x10, t), 0x10);
+
+	/* b = a + 1 */
+	KUNIT_EXPECT_EQ(test, lerp_u16(0x10, 0x11, t), 0x11);
+
+	/*** t = 0.0 ***/
+	t = 0x0;
+	KUNIT_EXPECT_EQ(test, lerp_u16(0x0, 0x10, t), 0x0);
+
+	/* odd a */
+	KUNIT_EXPECT_EQ(test, lerp_u16(0x1, 0x10, t), 0x1);
+
+	/* odd b */
+	KUNIT_EXPECT_EQ(test, lerp_u16(0x1, 0xf, t), 0x1);
+
+	/* b = a */
+	KUNIT_EXPECT_EQ(test, lerp_u16(0x10, 0x10, t), 0x10);
+
+	/* b = a + 1 */
+	KUNIT_EXPECT_EQ(test, lerp_u16(0x10, 0x11, t), 0x10);
+
+	/*** t = 1.0 ***/
+	t = 0x100000000;
+	KUNIT_EXPECT_EQ(test, lerp_u16(0x0, 0x10, t), 0x10);
+
+	/* odd a */
+	KUNIT_EXPECT_EQ(test, lerp_u16(0x1, 0x10, t), 0x10);
+
+	/* odd b */
+	KUNIT_EXPECT_EQ(test, lerp_u16(0x1, 0xf, t), 0xf);
+
+	/* b = a */
+	KUNIT_EXPECT_EQ(test, lerp_u16(0x10, 0x10, t), 0x10);
+
+	/* b = a + 1 */
+	KUNIT_EXPECT_EQ(test, lerp_u16(0x10, 0x11, t), 0x11);
+
+	/*** t = 0.0 + 1 ***/
+	t = 0x0 + 1;
+	KUNIT_EXPECT_EQ(test, lerp_u16(0x0, 0x10, t), 0x0);
+
+	/* odd a */
+	KUNIT_EXPECT_EQ(test, lerp_u16(0x1, 0x10, t), 0x1);
+
+	/* odd b */
+	KUNIT_EXPECT_EQ(test, lerp_u16(0x1, 0xf, t), 0x1);
+
+	/* b = a */
+	KUNIT_EXPECT_EQ(test, lerp_u16(0x10, 0x10, t), 0x10);
+
+	/* b = a + 1 */
+	KUNIT_EXPECT_EQ(test, lerp_u16(0x10, 0x11, t), 0x10);
+
+	/*** t = 1.0 - 1 ***/
+	t = 0x100000000 - 1;
+	KUNIT_EXPECT_EQ(test, lerp_u16(0x0, 0x10, t), 0x10);
+
+	/* odd a */
+	KUNIT_EXPECT_EQ(test, lerp_u16(0x1, 0x10, t), 0x10);
+
+	/* odd b */
+	KUNIT_EXPECT_EQ(test, lerp_u16(0x1, 0xf, t), 0xf);
+
+	/* b = a */
+	KUNIT_EXPECT_EQ(test, lerp_u16(0x10, 0x10, t), 0x10);
+
+	/* b = a + 1 */
+	KUNIT_EXPECT_EQ(test, lerp_u16(0x10, 0x11, t), 0x11);
+
+	/*** t chosen to verify the flipping point of result a (or b) to a+1 (or b-1) ***/
+	KUNIT_EXPECT_EQ(test, lerp_u16(0x0, 0x1, 0x80000000 - 1), 0x0);
+	KUNIT_EXPECT_EQ(test, lerp_u16(0x0, 0x1, 0x80000000), 0x1);
+}
+
+static struct kunit_case vkms_color_test_cases[] = {
+	KUNIT_CASE(vkms_color_test_get_lut_index),
+	KUNIT_CASE(vkms_color_test_lerp),
+	{}
+};
+
+static struct kunit_suite vkms_color_test_suite = {
+	.name = "vkms-color",
+	.test_cases = vkms_color_test_cases,
+};
+
+kunit_test_suite(vkms_color_test_suite);
+
+MODULE_DESCRIPTION("Kunit test for VKMS LUT handling");
+MODULE_LICENSE("GPL");
diff --git a/drivers/gpu/drm/vkms/vkms_composer.c b/drivers/gpu/drm/vkms/vkms_composer.c
index fa269d279e25..b0dc95f971d8 100644
--- a/drivers/gpu/drm/vkms/vkms_composer.c
+++ b/drivers/gpu/drm/vkms/vkms_composer.c
@@ -12,6 +12,8 @@
 #include <linux/minmax.h>
 
 #include "vkms_drv.h"
+#include <kunit/visibility.h>
+#include "vkms_composer.h"
 
 static u16 pre_mul_blend_channel(u16 src, u16 dst, u16 alpha)
 {
@@ -60,7 +62,7 @@ static void fill_background(const struct pixel_argb_u16 *background_color,
 }
 
 // lerp(a, b, t) = a + (b - a) * t
-static u16 lerp_u16(u16 a, u16 b, s64 t)
+VISIBLE_IF_KUNIT u16 lerp_u16(u16 a, u16 b, s64 t)
 {
 	s64 a_fp = drm_int2fixp(a);
 	s64 b_fp = drm_int2fixp(b);
@@ -69,13 +71,15 @@ static u16 lerp_u16(u16 a, u16 b, s64 t)
 
 	return drm_fixp2int_round(a_fp + delta);
 }
+EXPORT_SYMBOL_IF_KUNIT(lerp_u16);
 
-static s64 get_lut_index(const struct vkms_color_lut *lut, u16 channel_value)
+VISIBLE_IF_KUNIT s64 get_lut_index(const struct vkms_color_lut *lut, u16 channel_value)
 {
 	s64 color_channel_fp = drm_int2fixp(channel_value);
 
 	return drm_fixp_mul(color_channel_fp, lut->channel_value2index_ratio);
 }
+EXPORT_SYMBOL_IF_KUNIT(get_lut_index);
 
 /*
  * This enum is related to the positions of the variables inside
diff --git a/drivers/gpu/drm/vkms/vkms_composer.h b/drivers/gpu/drm/vkms/vkms_composer.h
new file mode 100644
index 000000000000..9316a053e7d7
--- /dev/null
+++ b/drivers/gpu/drm/vkms/vkms_composer.h
@@ -0,0 +1,13 @@
+/* SPDX-License-Identifier: GPL-2.0+ */
+
+#ifndef _VKMS_COMPOSER_H_
+#define _VKMS_COMPOSER_H_
+
+#include <kunit/visibility.h>
+
+#if IS_ENABLED(CONFIG_KUNIT)
+u16 lerp_u16(u16 a, u16 b, s64 t);
+s64 get_lut_index(const struct vkms_color_lut *lut, u16 channel_value);
+#endif
+
+#endif /* _VKMS_COMPOSER_H_ */
-- 
2.43.0