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, 143 insertions, 0 deletions

diff --git a/lib/tests/liveupdate.c b/lib/tests/liveupdate.c
new file mode 100644
index 000000000..4c08a7c6f
--- /dev/null
+++ b/lib/tests/liveupdate.c
@@ -0,0 +1,143 @@
+// SPDX-License-Identifier: GPL-2.0
+
+/*
+ * Copyright (c) 2025, Google LLC.
+ * Pasha Tatashin <pasha.tatashin@soleen.com>
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME " test: " fmt
+
+#include <linux/cleanup.h>
+#include <linux/errno.h>
+#include <linux/init.h>
+#include <linux/liveupdate.h>
+#include <linux/module.h>
+#include "../../kernel/liveupdate/luo_internal.h"
+
+static const struct liveupdate_flb_ops test_flb_ops;
+#define DEFINE_TEST_FLB(i) {						\
+	.ops = &test_flb_ops,						\
+	.compatible = LIVEUPDATE_TEST_FLB_COMPATIBLE(i),		\
+}
+
+/* Number of Test FLBs to register with every file handler */
+#define TEST_NFLBS 3
+static struct liveupdate_flb test_flbs[TEST_NFLBS] = {
+	DEFINE_TEST_FLB(0),
+	DEFINE_TEST_FLB(1),
+	DEFINE_TEST_FLB(2),
+};
+
+#define TEST_FLB_MAGIC_BASE 0xFEEDF00DCAFEBEE0ULL
+
+static int test_flb_preserve(struct liveupdate_flb_op_args *argp)
+{
+	ptrdiff_t index = argp->flb - test_flbs;
+
+	pr_info("%s: preserve was triggered\n", argp->flb->compatible);
+	argp->data = TEST_FLB_MAGIC_BASE + index;
+
+	return 0;
+}
+
+static void test_flb_unpreserve(struct liveupdate_flb_op_args *argp)
+{
+	pr_info("%s: unpreserve was triggered\n", argp->flb->compatible);
+}
+
+static int test_flb_retrieve(struct liveupdate_flb_op_args *argp)
+{
+	ptrdiff_t index = argp->flb - test_flbs;
+	u64 expected_data = TEST_FLB_MAGIC_BASE + index;
+
+	if (argp->data == expected_data) {
+		pr_info("%s: found flb data from the previous boot\n",
+			argp->flb->compatible);
+		argp->obj = (void *)argp->data;
+	} else {
+		pr_err("%s: ERROR - incorrect data handle: %llx, expected %llx\n",
+		       argp->flb->compatible, argp->data, expected_data);
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+static void test_flb_finish(struct liveupdate_flb_op_args *argp)
+{
+	ptrdiff_t index = argp->flb - test_flbs;
+	void *expected_obj = (void *)(TEST_FLB_MAGIC_BASE + index);
+
+	if (argp->obj == expected_obj) {
+		pr_info("%s: finish was triggered\n", argp->flb->compatible);
+	} else {
+		pr_err("%s: ERROR - finish called with invalid object\n",
+		       argp->flb->compatible);
+	}
+}
+
+static const struct liveupdate_flb_ops test_flb_ops = {
+	.preserve	= test_flb_preserve,
+	.unpreserve	= test_flb_unpreserve,
+	.retrieve	= test_flb_retrieve,
+	.finish		= test_flb_finish,
+	.owner		= THIS_MODULE,
+};
+
+static void liveupdate_test_init(void)
+{
+	static DEFINE_MUTEX(init_lock);
+	static bool initialized;
+	int i;
+
+	guard(mutex)(&init_lock);
+
+	if (initialized)
+		return;
+
+	for (i = 0; i < TEST_NFLBS; i++) {
+		struct liveupdate_flb *flb = &test_flbs[i];
+		void *obj;
+		int err;
+
+		err = liveupdate_flb_get_incoming(flb, &obj);
+		if (err && err != -ENODATA && err != -ENOENT) {
+			pr_err("liveupdate_flb_get_incoming for %s failed: %pe\n",
+			       flb->compatible, ERR_PTR(err));
+		}
+
+		if (!err)
+			liveupdate_flb_put_incoming(flb);
+	}
+	initialized = true;
+}
+
+void liveupdate_test_register(struct liveupdate_file_handler *fh)
+{
+	int err, i;
+
+	liveupdate_test_init();
+
+	for (i = 0; i < TEST_NFLBS; i++) {
+		struct liveupdate_flb *flb = &test_flbs[i];
+
+		err = liveupdate_register_flb(fh, flb);
+		if (err) {
+			pr_err("Failed to register %s %pe\n",
+			       flb->compatible, ERR_PTR(err));
+		}
+	}
+
+	err = liveupdate_register_flb(fh, &test_flbs[0]);
+	if (!err || err != -EEXIST) {
+		pr_err("Failed: %s should be already registered, but got err: %pe\n",
+		       test_flbs[0].compatible, ERR_PTR(err));
+	}
+
+	pr_info("Registered %d FLBs with file handler: [%s]\n",
+		TEST_NFLBS, fh->compatible);
+}
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Pasha Tatashin <pasha.tatashin@soleen.com>");
+MODULE_DESCRIPTION("In-kernel test for LUO mechanism");