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, 187 insertions, 0 deletions

diff --git a/drivers/mtd/devices/mtdram.c b/drivers/mtd/devices/mtdram.c
new file mode 100644
index 000000000..3fff3cdd9
--- /dev/null
+++ b/drivers/mtd/devices/mtdram.c
@@ -0,0 +1,187 @@
+/*
+ * mtdram - a test mtd device
+ * Author: Alexander Larsson <alex@cendio.se>
+ *
+ * Copyright (c) 1999 Alexander Larsson <alex@cendio.se>
+ * Copyright (c) 2005 Joern Engel <joern@wh.fh-wedel.de>
+ *
+ * This code is GPL
+ *
+ */
+
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/ioport.h>
+#include <linux/vmalloc.h>
+#include <linux/mm.h>
+#include <linux/init.h>
+#include <linux/mtd/mtd.h>
+#include <linux/mtd/mtdram.h>
+
+static unsigned long total_size = CONFIG_MTDRAM_TOTAL_SIZE;
+static unsigned long erase_size = CONFIG_MTDRAM_ERASE_SIZE;
+static unsigned long writebuf_size = 64;
+#define MTDRAM_TOTAL_SIZE (total_size * 1024)
+#define MTDRAM_ERASE_SIZE (erase_size * 1024)
+
+module_param(total_size, ulong, 0);
+MODULE_PARM_DESC(total_size, "Total device size in KiB");
+module_param(erase_size, ulong, 0);
+MODULE_PARM_DESC(erase_size, "Device erase block size in KiB");
+module_param(writebuf_size, ulong, 0);
+MODULE_PARM_DESC(writebuf_size, "Device write buf size in Bytes (Default: 64)");
+
+// We could store these in the mtd structure, but we only support 1 device..
+static struct mtd_info *mtd_info;
+
+static int check_offs_len(struct mtd_info *mtd, loff_t ofs, uint64_t len)
+{
+	int ret = 0;
+
+	/* Start address must align on block boundary */
+	if (mtd_mod_by_eb(ofs, mtd)) {
+		pr_debug("%s: unaligned address\n", __func__);
+		ret = -EINVAL;
+	}
+
+	/* Length must align on block boundary */
+	if (mtd_mod_by_eb(len, mtd)) {
+		pr_debug("%s: length not block aligned\n", __func__);
+		ret = -EINVAL;
+	}
+
+	return ret;
+}
+
+static int ram_erase(struct mtd_info *mtd, struct erase_info *instr)
+{
+	if (check_offs_len(mtd, instr->addr, instr->len))
+		return -EINVAL;
+	memset((char *)mtd->priv + instr->addr, 0xff, instr->len);
+
+	return 0;
+}
+
+static int ram_point(struct mtd_info *mtd, loff_t from, size_t len,
+		size_t *retlen, void **virt, resource_size_t *phys)
+{
+	*virt = mtd->priv + from;
+	*retlen = len;
+
+	if (phys) {
+		/* limit retlen to the number of contiguous physical pages */
+		unsigned long page_ofs = offset_in_page(*virt);
+		void *addr = *virt - page_ofs;
+		unsigned long pfn1, pfn0 = vmalloc_to_pfn(addr);
+
+		*phys = __pfn_to_phys(pfn0) + page_ofs;
+		len += page_ofs;
+		while (len > PAGE_SIZE) {
+			len -= PAGE_SIZE;
+			addr += PAGE_SIZE;
+			pfn0++;
+			pfn1 = vmalloc_to_pfn(addr);
+			if (pfn1 != pfn0) {
+				*retlen = addr - *virt;
+				break;
+			}
+		}
+	}
+
+	return 0;
+}
+
+static int ram_unpoint(struct mtd_info *mtd, loff_t from, size_t len)
+{
+	return 0;
+}
+
+static int ram_read(struct mtd_info *mtd, loff_t from, size_t len,
+		size_t *retlen, u_char *buf)
+{
+	memcpy(buf, mtd->priv + from, len);
+	*retlen = len;
+	return 0;
+}
+
+static int ram_write(struct mtd_info *mtd, loff_t to, size_t len,
+		size_t *retlen, const u_char *buf)
+{
+	memcpy((char *)mtd->priv + to, buf, len);
+	*retlen = len;
+	return 0;
+}
+
+static void __exit cleanup_mtdram(void)
+{
+	if (mtd_info) {
+		mtd_device_unregister(mtd_info);
+		vfree(mtd_info->priv);
+		kfree(mtd_info);
+	}
+}
+
+int mtdram_init_device(struct mtd_info *mtd, void *mapped_address,
+		unsigned long size, const char *name)
+{
+	memset(mtd, 0, sizeof(*mtd));
+
+	/* Setup the MTD structure */
+	mtd->name = name;
+	mtd->type = MTD_RAM;
+	mtd->flags = MTD_CAP_RAM;
+	mtd->size = size;
+	mtd->writesize = 1;
+	mtd->writebufsize = writebuf_size;
+	mtd->erasesize = MTDRAM_ERASE_SIZE;
+	mtd->priv = mapped_address;
+
+	mtd->owner = THIS_MODULE;
+	mtd->_erase = ram_erase;
+	mtd->_point = ram_point;
+	mtd->_unpoint = ram_unpoint;
+	mtd->_read = ram_read;
+	mtd->_write = ram_write;
+
+	if (mtd_device_register(mtd, NULL, 0))
+		return -EIO;
+
+	return 0;
+}
+
+static int __init init_mtdram(void)
+{
+	void *addr;
+	int err;
+
+	if (!total_size)
+		return -EINVAL;
+
+	/* Allocate some memory */
+	mtd_info = kmalloc_obj(struct mtd_info);
+	if (!mtd_info)
+		return -ENOMEM;
+
+	addr = vmalloc(MTDRAM_TOTAL_SIZE);
+	if (!addr) {
+		kfree(mtd_info);
+		mtd_info = NULL;
+		return -ENOMEM;
+	}
+	err = mtdram_init_device(mtd_info, addr, MTDRAM_TOTAL_SIZE, "mtdram test device");
+	if (err) {
+		vfree(addr);
+		kfree(mtd_info);
+		mtd_info = NULL;
+		return err;
+	}
+	memset(mtd_info->priv, 0xff, MTDRAM_TOTAL_SIZE);
+	return err;
+}
+
+module_init(init_mtdram);
+module_exit(cleanup_mtdram);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Alexander Larsson <alexl@redhat.com>");
+MODULE_DESCRIPTION("Simulated MTD driver for testing");