On Tue, Jan 20, 2026 at 02:56:26PM +0100, Andrew Lunn wrote:

quoted

+/* Note: the delay step value is at 0.1ps */
+static const unsigned int k3_delay_step_10x[4] = {
+	367, 493, 559, 685
+};

Am i reading it correctly that RGMII delays are limited to these four
values?

If so, please add this list to the DT binding.

No, these value are just adjustment interval, and it is also
controlled by another code register, the final delay is calculated
by the following formula:

delay = delay_step * delay_code * 0.9;

So the delay configuration needs to be calculated instead of
directly assigned.

quoted

+static int spacemit_dwmac_detected_delay_value(unsigned int delay,
+					       unsigned int *config)
+{
+	int i;
+	int code, best_code = 0;
+	unsigned int best_delay = 0;
+	unsigned int best_config = 0;
+
+	if (delay == 0)
+		return 0;
+
+	for (i = 0; i < ARRAY_SIZE(k3_delay_step_10x); i++) {
+		unsigned int step = k3_delay_step_10x[i];
+
+		for (code = 1; code <= MAX_DLINE_DELAY_CODE; code++) {
+			/*
+			 * Note K3 require a specific factor for calculate
+			 * the delay, in this scenario it is 0.9. So the
+			 * formula is code * step / 10 * 0.9
+			 */
+			unsigned int tmp = code * step * 9 / 10 / 10;
+
+			if (abs(tmp - delay) < abs(best_delay - delay)) {
+				best_code = code;
+				best_delay = tmp;
+				best_config = i;
+			}
+		}
+	}

With the four values listed in DT, i would make this a straight match,
not the nearest, and return -EINVAL otherwise.

    Andrew

Regards,
Inochi