int usb4_switch_credits_init()

in usb4.c [683:812]

• 104 lines of code
• 32 McCabe index (conditional complexity)

int usb4_switch_credits_init(struct tb_switch *sw)
{
	int max_usb3, min_dp_aux, min_dp_main, max_pcie, max_dma;
	int ret, length, i, nports;
	const struct tb_port *port;
	u32 data[NVM_DATA_DWORDS];
	u32 metadata = 0;
	u8 status = 0;

	memset(data, 0, sizeof(data));
	ret = usb4_switch_op_data(sw, USB4_SWITCH_OP_BUFFER_ALLOC, &metadata,
				  &status, NULL, 0, data, ARRAY_SIZE(data));
	if (ret)
		return ret;
	if (status)
		return -EIO;

	length = metadata & USB4_BA_LENGTH_MASK;
	if (WARN_ON(length > ARRAY_SIZE(data)))
		return -EMSGSIZE;

	max_usb3 = -1;
	min_dp_aux = -1;
	min_dp_main = -1;
	max_pcie = -1;
	max_dma = -1;

	tb_sw_dbg(sw, "credit allocation parameters:\n");

	for (i = 0; i < length; i++) {
		u16 index, value;

		index = data[i] & USB4_BA_INDEX_MASK;
		value = (data[i] & USB4_BA_VALUE_MASK) >> USB4_BA_VALUE_SHIFT;

		switch (index) {
		case USB4_BA_MAX_USB3:
			tb_sw_dbg(sw, " USB3: %u\n", value);
			max_usb3 = value;
			break;
		case USB4_BA_MIN_DP_AUX:
			tb_sw_dbg(sw, " DP AUX: %u\n", value);
			min_dp_aux = value;
			break;
		case USB4_BA_MIN_DP_MAIN:
			tb_sw_dbg(sw, " DP main: %u\n", value);
			min_dp_main = value;
			break;
		case USB4_BA_MAX_PCIE:
			tb_sw_dbg(sw, " PCIe: %u\n", value);
			max_pcie = value;
			break;
		case USB4_BA_MAX_HI:
			tb_sw_dbg(sw, " DMA: %u\n", value);
			max_dma = value;
			break;
		default:
			tb_sw_dbg(sw, " unknown credit allocation index %#x, skipping\n",
				  index);
			break;
		}
	}

	/*
	 * Validate the buffer allocation preferences. If we find
	 * issues, log a warning and fall back using the hard-coded
	 * values.
	 */

	/* Host router must report baMaxHI */
	if (!tb_route(sw) && max_dma < 0) {
		tb_sw_warn(sw, "host router is missing baMaxHI\n");
		goto err_invalid;
	}

	nports = 0;
	tb_switch_for_each_port(sw, port) {
		if (tb_port_is_null(port))
			nports++;
	}

	/* Must have DP buffer allocation (multiple USB4 ports) */
	if (nports > 2 && (min_dp_aux < 0 || min_dp_main < 0)) {
		tb_sw_warn(sw, "multiple USB4 ports require baMinDPaux/baMinDPmain\n");
		goto err_invalid;
	}

	tb_switch_for_each_port(sw, port) {
		if (tb_port_is_dpout(port) && min_dp_main < 0) {
			tb_sw_warn(sw, "missing baMinDPmain");
			goto err_invalid;
		}
		if ((tb_port_is_dpin(port) || tb_port_is_dpout(port)) &&
		    min_dp_aux < 0) {
			tb_sw_warn(sw, "missing baMinDPaux");
			goto err_invalid;
		}
		if ((tb_port_is_usb3_down(port) || tb_port_is_usb3_up(port)) &&
		    max_usb3 < 0) {
			tb_sw_warn(sw, "missing baMaxUSB3");
			goto err_invalid;
		}
		if ((tb_port_is_pcie_down(port) || tb_port_is_pcie_up(port)) &&
		    max_pcie < 0) {
			tb_sw_warn(sw, "missing baMaxPCIe");
			goto err_invalid;
		}
	}

	/*
	 * Buffer allocation passed the validation so we can use it in
	 * path creation.
	 */
	sw->credit_allocation = true;
	if (max_usb3 > 0)
		sw->max_usb3_credits = max_usb3;
	if (min_dp_aux > 0)
		sw->min_dp_aux_credits = min_dp_aux;
	if (min_dp_main > 0)
		sw->min_dp_main_credits = min_dp_main;
	if (max_pcie > 0)
		sw->max_pcie_credits = max_pcie;
	if (max_dma > 0)
		sw->max_dma_credits = max_dma;

	return 0;

err_invalid:
	return -EINVAL;
}