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, 142 insertions, 0 deletions

diff --git a/arch/powerpc/boot/ugecon.c b/arch/powerpc/boot/ugecon.c
new file mode 100644
index 000000000..938a38bd4
--- /dev/null
+++ b/arch/powerpc/boot/ugecon.c
@@ -0,0 +1,142 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * arch/powerpc/boot/ugecon.c
+ *
+ * USB Gecko bootwrapper console.
+ * Copyright (C) 2008-2009 The GameCube Linux Team
+ * Copyright (C) 2008,2009 Albert Herranz
+ */
+
+#include <stddef.h>
+#include "stdio.h"
+#include "types.h"
+#include "io.h"
+#include "ops.h"
+
+
+#define EXI_CLK_32MHZ           5
+
+#define EXI_CSR                 0x00
+#define   EXI_CSR_CLKMASK       (0x7<<4)
+#define     EXI_CSR_CLK_32MHZ   (EXI_CLK_32MHZ<<4)
+#define   EXI_CSR_CSMASK        (0x7<<7)
+#define     EXI_CSR_CS_0        (0x1<<7)  /* Chip Select 001 */
+
+#define EXI_CR                  0x0c
+#define   EXI_CR_TSTART         (1<<0)
+#define   EXI_CR_WRITE		(1<<2)
+#define   EXI_CR_READ_WRITE     (2<<2)
+#define   EXI_CR_TLEN(len)      (((len)-1)<<4)
+
+#define EXI_DATA                0x10
+
+
+/* virtual address base for input/output, retrieved from device tree */
+static void *ug_io_base;
+
+
+static u32 ug_io_transaction(u32 in)
+{
+	u32 *csr_reg = ug_io_base + EXI_CSR;
+	u32 *data_reg = ug_io_base + EXI_DATA;
+	u32 *cr_reg = ug_io_base + EXI_CR;
+	u32 csr, data, cr;
+
+	/* select */
+	csr = EXI_CSR_CLK_32MHZ | EXI_CSR_CS_0;
+	out_be32(csr_reg, csr);
+
+	/* read/write */
+	data = in;
+	out_be32(data_reg, data);
+	cr = EXI_CR_TLEN(2) | EXI_CR_READ_WRITE | EXI_CR_TSTART;
+	out_be32(cr_reg, cr);
+
+	while (in_be32(cr_reg) & EXI_CR_TSTART)
+		barrier();
+
+	/* deselect */
+	out_be32(csr_reg, 0);
+
+	data = in_be32(data_reg);
+	return data;
+}
+
+static int ug_is_txfifo_ready(void)
+{
+	return ug_io_transaction(0xc0000000) & 0x04000000;
+}
+
+static void ug_raw_putc(char ch)
+{
+	ug_io_transaction(0xb0000000 | (ch << 20));
+}
+
+static void ug_putc(char ch)
+{
+	int count = 16;
+
+	if (!ug_io_base)
+		return;
+
+	while (!ug_is_txfifo_ready() && count--)
+		barrier();
+	if (count >= 0)
+		ug_raw_putc(ch);
+}
+
+void ug_console_write(const char *buf, int len)
+{
+	char *b = (char *)buf;
+
+	while (len--) {
+		if (*b == '\n')
+			ug_putc('\r');
+		ug_putc(*b++);
+	}
+}
+
+static int ug_is_adapter_present(void)
+{
+	if (!ug_io_base)
+		return 0;
+	return ug_io_transaction(0x90000000) == 0x04700000;
+}
+
+static void *ug_grab_exi_io_base(void)
+{
+	u32 v;
+	void *devp;
+
+	devp = find_node_by_compatible(NULL, "nintendo,flipper-exi");
+	if (devp == NULL)
+		goto err_out;
+	if (getprop(devp, "virtual-reg", &v, sizeof(v)) != sizeof(v))
+		goto err_out;
+
+	return (void *)v;
+
+err_out:
+	return NULL;
+}
+
+void *ug_probe(void)
+{
+	void *exi_io_base;
+	int i;
+
+	exi_io_base = ug_grab_exi_io_base();
+	if (!exi_io_base)
+		return NULL;
+
+	/* look for a usbgecko on memcard slots A and B */
+	for (i = 0; i < 2; i++) {
+		ug_io_base = exi_io_base + 0x14 * i;
+		if (ug_is_adapter_present())
+			break;
+	}
+	if (i == 2)
+		ug_io_base = NULL;
+	return ug_io_base;
+}
+