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, 98 insertions, 0 deletions

diff --git a/drivers/rtc/rtc-sun4v.c b/drivers/rtc/rtc-sun4v.c
new file mode 100644
index 000000000..a86e27de8
--- /dev/null
+++ b/drivers/rtc/rtc-sun4v.c
@@ -0,0 +1,98 @@
+// SPDX-License-Identifier: GPL-2.0
+/* rtc-sun4v.c: Hypervisor based RTC for SUN4V systems.
+ *
+ * Author: David S. Miller
+ *
+ * Copyright (C) 2008 David S. Miller <davem@davemloft.net>
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/kernel.h>
+#include <linux/delay.h>
+#include <linux/init.h>
+#include <linux/rtc.h>
+#include <linux/platform_device.h>
+
+#include <asm/hypervisor.h>
+
+static unsigned long hypervisor_get_time(void)
+{
+	unsigned long ret, time;
+	int retries = 10000;
+
+retry:
+	ret = sun4v_tod_get(&time);
+	if (ret == HV_EOK)
+		return time;
+	if (ret == HV_EWOULDBLOCK) {
+		if (--retries > 0) {
+			udelay(100);
+			goto retry;
+		}
+		pr_warn("tod_get() timed out.\n");
+		return 0;
+	}
+	pr_warn("tod_get() not supported.\n");
+	return 0;
+}
+
+static int sun4v_read_time(struct device *dev, struct rtc_time *tm)
+{
+	rtc_time64_to_tm(hypervisor_get_time(), tm);
+	return 0;
+}
+
+static int hypervisor_set_time(unsigned long secs)
+{
+	unsigned long ret;
+	int retries = 10000;
+
+retry:
+	ret = sun4v_tod_set(secs);
+	if (ret == HV_EOK)
+		return 0;
+	if (ret == HV_EWOULDBLOCK) {
+		if (--retries > 0) {
+			udelay(100);
+			goto retry;
+		}
+		pr_warn("tod_set() timed out.\n");
+		return -EAGAIN;
+	}
+	pr_warn("tod_set() not supported.\n");
+	return -EOPNOTSUPP;
+}
+
+static int sun4v_set_time(struct device *dev, struct rtc_time *tm)
+{
+	return hypervisor_set_time(rtc_tm_to_time64(tm));
+}
+
+static const struct rtc_class_ops sun4v_rtc_ops = {
+	.read_time	= sun4v_read_time,
+	.set_time	= sun4v_set_time,
+};
+
+static int __init sun4v_rtc_probe(struct platform_device *pdev)
+{
+	struct rtc_device *rtc;
+
+	rtc = devm_rtc_allocate_device(&pdev->dev);
+	if (IS_ERR(rtc))
+		return PTR_ERR(rtc);
+
+	rtc->ops = &sun4v_rtc_ops;
+	rtc->range_max = U64_MAX;
+	platform_set_drvdata(pdev, rtc);
+
+	return devm_rtc_register_device(rtc);
+}
+
+static struct platform_driver sun4v_rtc_driver = {
+	.driver		= {
+		.name	= "rtc-sun4v",
+	},
+};
+
+builtin_platform_driver_probe(sun4v_rtc_driver, sun4v_rtc_probe);