Hi,

A few comments on this...

On Wed, Aug 13, 2025 at 10:55:32PM +0800, Chen-Yu Tsai wrote:

+#include "stmmac.h"
+#include "stmmac_platform.h"
+
+#define SYSCON_REG		0x34
+
+/* RMII specific bits */
+#define SYSCON_RMII_EN		BIT(13) /* 1: enable RMII (overrides EPIT) */
+/* Generic system control EMAC_CLK bits */
+#define SYSCON_ETXDC_MASK		GENMASK(12, 10)
+#define SYSCON_ERXDC_MASK		GENMASK(9, 5)
+/* EMAC PHY Interface Type */
+#define SYSCON_EPIT			BIT(2) /* 1: RGMII, 0: MII */
+#define SYSCON_ETCS_MASK		GENMASK(1, 0)
+#define SYSCON_ETCS_MII		0x0
+#define SYSCON_ETCS_EXT_GMII	0x1
+#define SYSCON_ETCS_INT_GMII	0x2
+
+#define MASK_TO_VAL(mask)   ((mask) >> (__builtin_ffsll(mask) - 1))

Is FIELD_GET() not sufficient?

+
+static int sun55i_gmac200_set_syscon(struct device *dev,
+				     struct plat_stmmacenet_data *plat)
+{
+	struct device_node *node = dev->of_node;
+	struct regmap *regmap;
+	u32 val, reg = 0;
+	int ret;
+
+	regmap = syscon_regmap_lookup_by_phandle(node, "syscon");
+	if (IS_ERR(regmap))
+		return dev_err_probe(dev, PTR_ERR(regmap), "Unable to map syscon\n");
+
+	if (!of_property_read_u32(node, "tx-internal-delay-ps", &val)) {
+		if (val % 100)
+			return dev_err_probe(dev, -EINVAL,
+					     "tx-delay must be a multiple of 100\n");

	"tx-delay must be a multiple of 100ps\n"

would be a bit better.

+		val /= 100;
+		dev_dbg(dev, "set tx-delay to %x\n", val);
+		if (val > MASK_TO_VAL(SYSCON_ETXDC_MASK))
+			return dev_err_probe(dev, -EINVAL,
+					     "Invalid TX clock delay: %d\n",
+					     val);

		if (!FIELD_FIT(SYSCON_ETXDC_MASK, val))
			return dev_err_probe(dev, -EINVAL,
					    "TX clock delay exceeds maximum (%d00ps > %d00ps)\n",
					    val, FIELD_MAX(SYSCON_ETXDC_MASK));

+
+		reg |= FIELD_PREP(SYSCON_ETXDC_MASK, val);
+	}
+
+	if (!of_property_read_u32(node, "rx-internal-delay-ps", &val)) {
+		if (val % 100)
+			return dev_err_probe(dev, -EINVAL,
+					     "rx-delay must be a multiple of 100\n");
+		val /= 100;
+		dev_dbg(dev, "set rx-delay to %x\n", val);
+		if (val > MASK_TO_VAL(SYSCON_ERXDC_MASK))
+			return dev_err_probe(dev, -EINVAL,
+					     "Invalid RX clock delay: %d\n",
+					     val);

all the same points in this block.

Thanks.

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