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, 144 insertions, 0 deletions

diff --git a/drivers/acpi/ec_sys.c b/drivers/acpi/ec_sys.c
new file mode 100644
index 000000000..c074a0fae
--- /dev/null
+++ b/drivers/acpi/ec_sys.c
@@ -0,0 +1,144 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * ec_sys.c
+ *
+ * Copyright (C) 2010 SUSE Products GmbH/Novell
+ * Author:
+ *      Thomas Renninger <trenn@suse.de>
+ */
+
+#include <linux/kernel.h>
+#include <linux/acpi.h>
+#include <linux/debugfs.h>
+#include <linux/module.h>
+#include <linux/uaccess.h>
+#include "internal.h"
+
+MODULE_AUTHOR("Thomas Renninger <trenn@suse.de>");
+MODULE_DESCRIPTION("ACPI EC sysfs access driver");
+MODULE_LICENSE("GPL");
+
+static bool write_support;
+module_param_hw(write_support, bool, other, 0644);
+MODULE_PARM_DESC(write_support, "Dangerous, reboot and removal of battery may "
+		 "be needed.");
+
+#define EC_SPACE_SIZE 256
+
+static struct dentry *acpi_ec_debugfs_dir;
+
+static ssize_t acpi_ec_read_io(struct file *f, char __user *buf,
+			       size_t count, loff_t *off)
+{
+	/* Use this if support reading/writing multiple ECs exists in ec.c:
+	 * struct acpi_ec *ec = ((struct seq_file *)f->private_data)->private;
+	 */
+	unsigned int size = EC_SPACE_SIZE;
+	loff_t init_off = *off;
+	int err = 0;
+
+	if (*off >= size)
+		return 0;
+	if (*off + count >= size) {
+		size -= *off;
+		count = size;
+	} else
+		size = count;
+
+	while (size) {
+		u8 byte_read;
+		err = ec_read(*off, &byte_read);
+		if (err)
+			return err;
+		if (put_user(byte_read, buf + *off - init_off)) {
+			if (*off - init_off)
+				return *off - init_off; /* partial read */
+			return -EFAULT;
+		}
+		*off += 1;
+		size--;
+	}
+	return count;
+}
+
+static ssize_t acpi_ec_write_io(struct file *f, const char __user *buf,
+				size_t count, loff_t *off)
+{
+	/* Use this if support reading/writing multiple ECs exists in ec.c:
+	 * struct acpi_ec *ec = ((struct seq_file *)f->private_data)->private;
+	 */
+
+	unsigned int size = count;
+	loff_t init_off = *off;
+	int err = 0;
+
+	if (!write_support)
+		return -EINVAL;
+
+	if (*off >= EC_SPACE_SIZE)
+		return 0;
+	if (*off + count >= EC_SPACE_SIZE) {
+		size = EC_SPACE_SIZE - *off;
+		count = size;
+	}
+
+	while (size) {
+		u8 byte_write;
+		if (get_user(byte_write, buf + *off - init_off)) {
+			if (*off - init_off)
+				return *off - init_off; /* partial write */
+			return -EFAULT;
+		}
+		err = ec_write(*off, byte_write);
+		if (err)
+			return err;
+
+		*off += 1;
+		size--;
+	}
+	return count;
+}
+
+static const struct file_operations acpi_ec_io_ops = {
+	.owner = THIS_MODULE,
+	.open  = simple_open,
+	.read  = acpi_ec_read_io,
+	.write = acpi_ec_write_io,
+	.llseek = default_llseek,
+};
+
+static void acpi_ec_add_debugfs(struct acpi_ec *ec, unsigned int ec_device_count)
+{
+	struct dentry *dev_dir;
+	char name[64];
+	umode_t mode = 0400;
+
+	if (ec_device_count == 0)
+		acpi_ec_debugfs_dir = debugfs_create_dir("ec", NULL);
+
+	sprintf(name, "ec%u", ec_device_count);
+	dev_dir = debugfs_create_dir(name, acpi_ec_debugfs_dir);
+
+	debugfs_create_x32("gpe", 0444, dev_dir, &first_ec->gpe);
+	debugfs_create_bool("use_global_lock", 0444, dev_dir,
+			    &first_ec->global_lock);
+
+	if (write_support)
+		mode = 0600;
+	debugfs_create_file("io", mode, dev_dir, ec, &acpi_ec_io_ops);
+}
+
+static int __init acpi_ec_sys_init(void)
+{
+	if (first_ec)
+		acpi_ec_add_debugfs(first_ec, 0);
+	return 0;
+}
+
+static void __exit acpi_ec_sys_exit(void)
+{
+	debugfs_remove_recursive(acpi_ec_debugfs_dir);
+}
+
+module_init(acpi_ec_sys_init);
+module_exit(acpi_ec_sys_exit);