Re: [PATCH net-next 3/3] net: stmmac: Add glue layer for Spacemit K3 SoC

Andrew Lunn
2026-01-20T13:56:56Z

> +/* 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.

> +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