drm/amd/display: Try RGB before YCbCr 4:4:4 in stream validationgrafted

amdgpu_dm_create_validate_stream_for_sink() walks encoding_order[] and
uses the first encoding that validates. YCbCr 4:4:4 is listed before
RGB, so an HDMI sink that advertises 4:4:4 gets YCbCr 4:4:4 whenever the
"color format" property is left at AUTO, even though RGB fits the same
link.

That contradicts the documented AUTO behaviour for HDMI in enum
drm_connector_color_format (RGB, falling back to YCbCr 4:2:0 only when
the bandwidth is not available or the mode is 4:2:0-only), which the
amdgpu implementation of the property also describes. It also leaves
the "Broadcast RGB" property without effect on such sinks, since the
quantization range it selects only applies to RGB output.

Try RGB first. The mask still holds every encoding the sink supports,
so a mode that cannot carry RGB falls back exactly as before.

For reference, v7.2 picked RGB here unless YCbCr 4:4:4 was forced
through debugfs, while earlier kernels picked YCbCr 4:4:4 for any HDMI
sink that advertised it.

Fixes: 0b0ff65d3ca1 ("drm/amd/display: Refactor stream validation")
Suggested-by: Adolfo Rodrigues <adolfotregosa@gmail.com>
Assisted-by: Claude Code:claude-fable-5-1
Signed-off-by: Adrian Betschart <adrian.betschart@cinemaone.ch>
Reviewed-by: Fangzhi Zuo <jerry.zuo@amd.com>
Tested-by: Adolfo Rodrigues <adolfotregosa@gmail.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
(cherry picked from commit 7de432bc753133764dc40d37f9388da56de251e7)

1 files changed, 132 insertions, 0 deletions

diff --git a/drivers/leds/led-test.c b/drivers/leds/led-test.c
new file mode 100644
index 000000000..ddf9aa967
--- /dev/null
+++ b/drivers/leds/led-test.c
@@ -0,0 +1,132 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2025 Google LLC
+ *
+ * Author: Lee Jones <lee@kernel.org>
+ */
+
+#include <kunit/device.h>
+#include <kunit/test.h>
+#include <linux/device.h>
+#include <linux/leds.h>
+
+#define LED_TEST_POST_REG_BRIGHTNESS 10
+
+struct led_test_ddata {
+	struct led_classdev cdev;
+	struct device *dev;
+};
+
+static enum led_brightness led_test_brightness_get(struct led_classdev *cdev)
+{
+	return LED_TEST_POST_REG_BRIGHTNESS;
+}
+
+static void led_test_class_register(struct kunit *test)
+{
+	struct led_test_ddata *ddata = test->priv;
+	struct led_classdev *cdev_clash, *cdev = &ddata->cdev;
+	struct device *dev = ddata->dev;
+	int ret;
+
+	/* Register a LED class device */
+	cdev->name = "led-test";
+	cdev->brightness_get = led_test_brightness_get;
+	cdev->brightness = 0;
+
+	ret = devm_led_classdev_register(dev, cdev);
+	KUNIT_ASSERT_EQ(test, ret, 0);
+
+	KUNIT_EXPECT_EQ(test, cdev->max_brightness, LED_FULL);
+	KUNIT_EXPECT_EQ(test, cdev->brightness, LED_TEST_POST_REG_BRIGHTNESS);
+	KUNIT_EXPECT_STREQ(test, cdev->dev->kobj.name, "led-test");
+
+	/* Register again with the same name - expect it to pass with the LED renamed */
+	cdev_clash = devm_kmemdup(dev, cdev, sizeof(*cdev), GFP_KERNEL);
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, cdev_clash);
+
+	ret = devm_led_classdev_register(dev, cdev_clash);
+	KUNIT_ASSERT_EQ(test, ret, 0);
+
+	KUNIT_EXPECT_STREQ(test, cdev_clash->dev->kobj.name, "led-test_1");
+	KUNIT_EXPECT_STREQ(test, cdev_clash->name, "led-test");
+
+	/* Enable name conflict rejection and register with the same name again - expect failure */
+	cdev_clash->flags |= LED_REJECT_NAME_CONFLICT;
+	ret = devm_led_classdev_register(dev, cdev_clash);
+	KUNIT_EXPECT_EQ(test, ret, -EEXIST);
+}
+
+static void led_test_class_add_lookup_and_get(struct kunit *test)
+{
+	struct led_test_ddata *ddata = test->priv;
+	struct led_classdev *cdev = &ddata->cdev, *cdev_get;
+	struct device *dev = ddata->dev;
+	struct led_lookup_data lookup;
+	int ret;
+
+	/* First, register a LED class device */
+	cdev->name = "led-test";
+	ret = devm_led_classdev_register(dev, cdev);
+	KUNIT_ASSERT_EQ(test, ret, 0);
+
+	/* Then make the LED available for lookup */
+	lookup.provider = cdev->name;
+	lookup.dev_id = dev_name(dev);
+	lookup.con_id = "led-test-1";
+	led_add_lookup(&lookup);
+
+	/* Finally, attempt to look it up via the API - imagine this was an orthogonal driver */
+	cdev_get = devm_led_get(dev, "led-test-1");
+	KUNIT_ASSERT_FALSE(test, IS_ERR(cdev_get));
+
+	KUNIT_EXPECT_STREQ(test, cdev_get->name, cdev->name);
+
+	led_remove_lookup(&lookup);
+}
+
+static struct kunit_case led_test_cases[] = {
+	KUNIT_CASE(led_test_class_register),
+	KUNIT_CASE(led_test_class_add_lookup_and_get),
+	{ }
+};
+
+static int led_test_init(struct kunit *test)
+{
+	struct led_test_ddata *ddata;
+	struct device *dev;
+
+	ddata = kunit_kzalloc(test, sizeof(*ddata), GFP_KERNEL);
+	if (!ddata)
+		return -ENOMEM;
+
+	test->priv = ddata;
+
+	dev = kunit_device_register(test, "led_test");
+	if (IS_ERR(dev))
+		return PTR_ERR(dev);
+
+	ddata->dev = get_device(dev);
+
+	return 0;
+}
+
+static void led_test_exit(struct kunit *test)
+{
+	struct led_test_ddata *ddata = test->priv;
+
+	if (ddata && ddata->dev)
+		put_device(ddata->dev);
+}
+
+static struct kunit_suite led_test_suite = {
+	.name = "led",
+	.init = led_test_init,
+	.exit = led_test_exit,
+	.test_cases = led_test_cases,
+};
+kunit_test_suite(led_test_suite);
+
+MODULE_AUTHOR("Lee Jones <lee@kernel.org>");
+MODULE_DESCRIPTION("KUnit tests for the LED framework");
+MODULE_LICENSE("GPL");