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, 185 insertions, 0 deletions

diff --git a/arch/powerpc/boot/libfdt-wrapper.c b/arch/powerpc/boot/libfdt-wrapper.c
new file mode 100644
index 000000000..217d0d7a6
--- /dev/null
+++ b/arch/powerpc/boot/libfdt-wrapper.c
@@ -0,0 +1,185 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * This file does the necessary interface mapping between the bootwrapper
+ * device tree operations and the interface provided by shared source
+ * files flatdevicetree.[ch].
+ *
+ * Copyright 2007 David Gibson, IBM Corporation.
+ */
+
+#include <stddef.h>
+#include <stdio.h>
+#include <page.h>
+#include <libfdt.h>
+#include "ops.h"
+
+#define DEBUG	0
+#define BAD_ERROR(err)	(((err) < 0) \
+			 && ((err) != -FDT_ERR_NOTFOUND) \
+			 && ((err) != -FDT_ERR_EXISTS))
+
+#define check_err(err) \
+	({ \
+		if (BAD_ERROR(err) || ((err < 0) && DEBUG)) \
+			printf("%s():%d  %s\n\r", __func__, __LINE__, \
+			       fdt_strerror(err)); \
+		if (BAD_ERROR(err)) \
+			exit(); \
+		(err < 0) ? -1 : 0; \
+	})
+
+#define offset_devp(off)	\
+	({ \
+		unsigned long _offset = (off); \
+		check_err(_offset) ? NULL : (void *)(_offset+1); \
+	})
+
+#define devp_offset_find(devp)	(((unsigned long)(devp))-1)
+#define devp_offset(devp)	(devp ? ((unsigned long)(devp))-1 : 0)
+
+static void *fdt;
+static void *buf; /* = NULL */
+
+#define EXPAND_GRANULARITY	1024
+
+static void expand_buf(int minexpand)
+{
+	int size = fdt_totalsize(fdt);
+	int rc;
+
+	size = _ALIGN(size + minexpand, EXPAND_GRANULARITY);
+	buf = platform_ops.realloc(buf, size);
+	if (!buf)
+		fatal("Couldn't find %d bytes to expand device tree\n\r", size);
+	rc = fdt_open_into(fdt, buf, size);
+	if (rc != 0)
+		fatal("Couldn't expand fdt into new buffer: %s\n\r",
+		      fdt_strerror(rc));
+
+	fdt = buf;
+}
+
+static void *fdt_wrapper_finddevice(const char *path)
+{
+	return offset_devp(fdt_path_offset(fdt, path));
+}
+
+static int fdt_wrapper_getprop(const void *devp, const char *name,
+			       void *buf, const int buflen)
+{
+	const void *p;
+	int len;
+
+	p = fdt_getprop(fdt, devp_offset(devp), name, &len);
+	if (!p)
+		return check_err(len);
+	memcpy(buf, p, min(len, buflen));
+	return len;
+}
+
+static int fdt_wrapper_setprop(const void *devp, const char *name,
+			       const void *buf, const int len)
+{
+	int rc;
+
+	rc = fdt_setprop(fdt, devp_offset(devp), name, buf, len);
+	if (rc == -FDT_ERR_NOSPACE) {
+		expand_buf(len + 16);
+		rc = fdt_setprop(fdt, devp_offset(devp), name, buf, len);
+	}
+
+	return check_err(rc);
+}
+
+static int fdt_wrapper_del_node(const void *devp)
+{
+	return fdt_del_node(fdt, devp_offset(devp));
+}
+
+static void *fdt_wrapper_get_parent(const void *devp)
+{
+	return offset_devp(fdt_parent_offset(fdt, devp_offset(devp)));
+}
+
+static void *fdt_wrapper_create_node(const void *devp, const char *name)
+{
+	int offset;
+
+	offset = fdt_add_subnode(fdt, devp_offset(devp), name);
+	if (offset == -FDT_ERR_NOSPACE) {
+		expand_buf(strlen(name) + 16);
+		offset = fdt_add_subnode(fdt, devp_offset(devp), name);
+	}
+
+	return offset_devp(offset);
+}
+
+static void *fdt_wrapper_find_node_by_prop_value(const void *prev,
+						 const char *name,
+						 const char *val,
+						 int len)
+{
+	int offset = fdt_node_offset_by_prop_value(fdt, devp_offset_find(prev),
+	                                           name, val, len);
+	return offset_devp(offset);
+}
+
+static void *fdt_wrapper_find_node_by_compatible(const void *prev,
+						 const char *val)
+{
+	int offset = fdt_node_offset_by_compatible(fdt, devp_offset_find(prev),
+	                                           val);
+	return offset_devp(offset);
+}
+
+static char *fdt_wrapper_get_path(const void *devp, char *buf, int len)
+{
+	int rc;
+
+	rc = fdt_get_path(fdt, devp_offset(devp), buf, len);
+	if (check_err(rc))
+		return NULL;
+	return buf;
+}
+
+static unsigned long fdt_wrapper_finalize(void)
+{
+	int rc;
+
+	rc = fdt_pack(fdt);
+	if (rc != 0)
+		fatal("Couldn't pack flat tree: %s\n\r",
+		      fdt_strerror(rc));
+	return (unsigned long)fdt;
+}
+
+void fdt_init(void *blob)
+{
+	int err;
+	int bufsize;
+
+	dt_ops.finddevice = fdt_wrapper_finddevice;
+	dt_ops.getprop = fdt_wrapper_getprop;
+	dt_ops.setprop = fdt_wrapper_setprop;
+	dt_ops.get_parent = fdt_wrapper_get_parent;
+	dt_ops.create_node = fdt_wrapper_create_node;
+	dt_ops.find_node_by_prop_value = fdt_wrapper_find_node_by_prop_value;
+	dt_ops.find_node_by_compatible = fdt_wrapper_find_node_by_compatible;
+	dt_ops.del_node = fdt_wrapper_del_node;
+	dt_ops.get_path = fdt_wrapper_get_path;
+	dt_ops.finalize = fdt_wrapper_finalize;
+
+	/* Make sure the dt blob is the right version and so forth */
+	fdt = blob;
+	bufsize = fdt_totalsize(fdt) + EXPAND_GRANULARITY;
+	buf = malloc(bufsize);
+	if(!buf)
+		fatal("malloc failed. can't relocate the device tree\n\r");
+
+	err = fdt_open_into(fdt, buf, bufsize);
+
+	if (err != 0)
+		fatal("fdt_init(): %s\n\r", fdt_strerror(err));
+
+	fdt = buf;
+}