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, 157 insertions, 0 deletions

diff --git a/drivers/nvmem/snvs_lpgpr.c b/drivers/nvmem/snvs_lpgpr.c
new file mode 100644
index 000000000..89c271123
--- /dev/null
+++ b/drivers/nvmem/snvs_lpgpr.c
@@ -0,0 +1,157 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (c) 2015 Pengutronix, Steffen Trumtrar <kernel@pengutronix.de>
+ * Copyright (c) 2017 Pengutronix, Oleksij Rempel <kernel@pengutronix.de>
+ */
+
+#include <linux/mfd/syscon.h>
+#include <linux/module.h>
+#include <linux/nvmem-provider.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/regmap.h>
+
+#define IMX6Q_SNVS_HPLR		0x00
+#define IMX6Q_SNVS_LPLR		0x34
+#define IMX6Q_SNVS_LPGPR	0x68
+
+#define IMX7D_SNVS_HPLR		0x00
+#define IMX7D_SNVS_LPLR		0x34
+#define IMX7D_SNVS_LPGPR	0x90
+
+#define IMX_GPR_SL		BIT(5)
+#define IMX_GPR_HL		BIT(5)
+
+struct snvs_lpgpr_cfg {
+	int offset;
+	int offset_hplr;
+	int offset_lplr;
+	int size;
+};
+
+struct snvs_lpgpr_priv {
+	struct device_d			*dev;
+	struct regmap			*regmap;
+	struct nvmem_config		cfg;
+	const struct snvs_lpgpr_cfg	*dcfg;
+};
+
+static const struct snvs_lpgpr_cfg snvs_lpgpr_cfg_imx6q = {
+	.offset		= IMX6Q_SNVS_LPGPR,
+	.offset_hplr	= IMX6Q_SNVS_HPLR,
+	.offset_lplr	= IMX6Q_SNVS_LPLR,
+	.size		= 4,
+};
+
+static const struct snvs_lpgpr_cfg snvs_lpgpr_cfg_imx7d = {
+	.offset		= IMX7D_SNVS_LPGPR,
+	.offset_hplr	= IMX7D_SNVS_HPLR,
+	.offset_lplr	= IMX7D_SNVS_LPLR,
+	.size		= 16,
+};
+
+static int snvs_lpgpr_write(void *context, unsigned int offset, void *val,
+			    size_t bytes)
+{
+	struct snvs_lpgpr_priv *priv = context;
+	const struct snvs_lpgpr_cfg *dcfg = priv->dcfg;
+	unsigned int lock_reg;
+	int ret;
+
+	ret = regmap_read(priv->regmap, dcfg->offset_hplr, &lock_reg);
+	if (ret < 0)
+		return ret;
+
+	if (lock_reg & IMX_GPR_SL)
+		return -EPERM;
+
+	ret = regmap_read(priv->regmap, dcfg->offset_lplr, &lock_reg);
+	if (ret < 0)
+		return ret;
+
+	if (lock_reg & IMX_GPR_HL)
+		return -EPERM;
+
+	return regmap_bulk_write(priv->regmap, dcfg->offset + offset, val,
+				bytes / 4);
+}
+
+static int snvs_lpgpr_read(void *context, unsigned int offset, void *val,
+			   size_t bytes)
+{
+	struct snvs_lpgpr_priv *priv = context;
+	const struct snvs_lpgpr_cfg *dcfg = priv->dcfg;
+
+	return regmap_bulk_read(priv->regmap, dcfg->offset + offset,
+			       val, bytes / 4);
+}
+
+static int snvs_lpgpr_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct device_node *node = dev->of_node;
+	struct device_node *syscon_node;
+	struct snvs_lpgpr_priv *priv;
+	struct nvmem_config *cfg;
+	struct nvmem_device *nvmem;
+	const struct snvs_lpgpr_cfg *dcfg;
+
+	if (!node)
+		return -ENOENT;
+
+	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	dcfg = of_device_get_match_data(dev);
+	if (!dcfg)
+		return -EINVAL;
+
+	syscon_node = of_get_parent(node);
+	if (!syscon_node)
+		return -ENODEV;
+
+	priv->regmap = syscon_node_to_regmap(syscon_node);
+	of_node_put(syscon_node);
+	if (IS_ERR(priv->regmap))
+		return PTR_ERR(priv->regmap);
+
+	priv->dcfg = dcfg;
+
+	cfg = &priv->cfg;
+	cfg->priv = priv;
+	cfg->name = dev_name(dev);
+	cfg->dev = dev;
+	cfg->stride = 4;
+	cfg->word_size = 4;
+	cfg->size = dcfg->size;
+	cfg->owner = THIS_MODULE;
+	cfg->reg_read  = snvs_lpgpr_read;
+	cfg->reg_write = snvs_lpgpr_write;
+
+	nvmem = devm_nvmem_register(dev, cfg);
+
+	return PTR_ERR_OR_ZERO(nvmem);
+}
+
+static const struct of_device_id snvs_lpgpr_dt_ids[] = {
+	{ .compatible = "fsl,imx6q-snvs-lpgpr", .data = &snvs_lpgpr_cfg_imx6q },
+	{ .compatible = "fsl,imx6ul-snvs-lpgpr",
+	  .data = &snvs_lpgpr_cfg_imx6q },
+	{ .compatible = "fsl,imx7d-snvs-lpgpr",	.data = &snvs_lpgpr_cfg_imx7d },
+	{ },
+};
+MODULE_DEVICE_TABLE(of, snvs_lpgpr_dt_ids);
+
+static struct platform_driver snvs_lpgpr_driver = {
+	.probe	= snvs_lpgpr_probe,
+	.driver = {
+		.name	= "snvs_lpgpr",
+		.of_match_table = snvs_lpgpr_dt_ids,
+	},
+};
+module_platform_driver(snvs_lpgpr_driver);
+
+MODULE_AUTHOR("Oleksij Rempel <o.rempel@pengutronix.de>");
+MODULE_DESCRIPTION("Low Power General Purpose Register in i.MX6 and i.MX7 Secure Non-Volatile Storage");
+MODULE_LICENSE("GPL v2");