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, 92 insertions, 0 deletions

diff --git a/drivers/firmware/efi/efibc.c b/drivers/firmware/efi/efibc.c
new file mode 100644
index 000000000..345a10aa7
--- /dev/null
+++ b/drivers/firmware/efi/efibc.c
@@ -0,0 +1,92 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * efibc: control EFI bootloaders which obey LoaderEntryOneShot var
+ * Copyright (c) 2013-2016, Intel Corporation.
+ */
+
+#define pr_fmt(fmt) "efibc: " fmt
+
+#include <linux/efi.h>
+#include <linux/module.h>
+#include <linux/reboot.h>
+#include <linux/slab.h>
+#include <linux/ucs2_string.h>
+
+#define MAX_DATA_LEN	512
+
+static int efibc_set_variable(efi_char16_t *name, efi_char16_t *value,
+			      unsigned long len)
+{
+	efi_status_t status;
+
+	status = efi.set_variable(name, &LINUX_EFI_LOADER_ENTRY_GUID,
+				  EFI_VARIABLE_NON_VOLATILE
+				  | EFI_VARIABLE_BOOTSERVICE_ACCESS
+				  | EFI_VARIABLE_RUNTIME_ACCESS,
+				  len * sizeof(efi_char16_t), value);
+
+	if (status != EFI_SUCCESS) {
+		pr_err("failed to set EFI variable: 0x%lx\n", status);
+		return -EIO;
+	}
+	return 0;
+}
+
+static int efibc_reboot_notifier_call(struct notifier_block *notifier,
+				      unsigned long event, void *data)
+{
+	efi_char16_t *reason = event == SYS_RESTART ? L"reboot"
+						    : L"shutdown";
+	const u8 *str = data;
+	efi_char16_t *wdata;
+	unsigned long l;
+	int ret;
+
+	ret = efibc_set_variable(L"LoaderEntryRebootReason", reason,
+				 ucs2_strlen(reason));
+	if (ret || !data)
+		return NOTIFY_DONE;
+
+	wdata = kmalloc_objs(efi_char16_t, MAX_DATA_LEN);
+	if (!wdata)
+		return NOTIFY_DONE;
+
+	for (l = 0; l < MAX_DATA_LEN - 1 && str[l] != '\0'; l++)
+		wdata[l] = str[l];
+	wdata[l] = L'\0';
+
+	efibc_set_variable(L"LoaderEntryOneShot", wdata, l);
+
+	kfree(wdata);
+	return NOTIFY_DONE;
+}
+
+static struct notifier_block efibc_reboot_notifier = {
+	.notifier_call = efibc_reboot_notifier_call,
+};
+
+static int __init efibc_init(void)
+{
+	int ret;
+
+	if (!efi_rt_services_supported(EFI_RT_SUPPORTED_SET_VARIABLE))
+		return -ENODEV;
+
+	ret = register_reboot_notifier(&efibc_reboot_notifier);
+	if (ret)
+		pr_err("unable to register reboot notifier\n");
+
+	return ret;
+}
+module_init(efibc_init);
+
+static void __exit efibc_exit(void)
+{
+	unregister_reboot_notifier(&efibc_reboot_notifier);
+}
+module_exit(efibc_exit);
+
+MODULE_AUTHOR("Jeremy Compostella <jeremy.compostella@intel.com>");
+MODULE_AUTHOR("Matt Gumbel <matthew.k.gumbel@intel.com");
+MODULE_DESCRIPTION("EFI Bootloader Control");
+MODULE_LICENSE("GPL v2");