static int tb_dp_xchg_caps()

in tunnel.c [501:585]

• 54 lines of code
• 10 McCabe index (conditional complexity)

static int tb_dp_xchg_caps(struct tb_tunnel *tunnel)
{
	u32 out_dp_cap, out_rate, out_lanes, in_dp_cap, in_rate, in_lanes, bw;
	struct tb_port *out = tunnel->dst_port;
	struct tb_port *in = tunnel->src_port;
	int ret, max_bw;

	/*
	 * Copy DP_LOCAL_CAP register to DP_REMOTE_CAP register for
	 * newer generation hardware.
	 */
	if (in->sw->generation < 2 || out->sw->generation < 2)
		return 0;

	/*
	 * Perform connection manager handshake between IN and OUT ports
	 * before capabilities exchange can take place.
	 */
	ret = tb_dp_cm_handshake(in, out);
	if (ret)
		return ret;

	/* Read both DP_LOCAL_CAP registers */
	ret = tb_port_read(in, &in_dp_cap, TB_CFG_PORT,
			   in->cap_adap + DP_LOCAL_CAP, 1);
	if (ret)
		return ret;

	ret = tb_port_read(out, &out_dp_cap, TB_CFG_PORT,
			   out->cap_adap + DP_LOCAL_CAP, 1);
	if (ret)
		return ret;

	/* Write IN local caps to OUT remote caps */
	ret = tb_port_write(out, &in_dp_cap, TB_CFG_PORT,
			    out->cap_adap + DP_REMOTE_CAP, 1);
	if (ret)
		return ret;

	in_rate = tb_dp_cap_get_rate(in_dp_cap);
	in_lanes = tb_dp_cap_get_lanes(in_dp_cap);
	tb_port_dbg(in, "maximum supported bandwidth %u Mb/s x%u = %u Mb/s\n",
		    in_rate, in_lanes, tb_dp_bandwidth(in_rate, in_lanes));

	/*
	 * If the tunnel bandwidth is limited (max_bw is set) then see
	 * if we need to reduce bandwidth to fit there.
	 */
	out_rate = tb_dp_cap_get_rate(out_dp_cap);
	out_lanes = tb_dp_cap_get_lanes(out_dp_cap);
	bw = tb_dp_bandwidth(out_rate, out_lanes);
	tb_port_dbg(out, "maximum supported bandwidth %u Mb/s x%u = %u Mb/s\n",
		    out_rate, out_lanes, bw);

	if (in->sw->config.depth < out->sw->config.depth)
		max_bw = tunnel->max_down;
	else
		max_bw = tunnel->max_up;

	if (max_bw && bw > max_bw) {
		u32 new_rate, new_lanes, new_bw;

		ret = tb_dp_reduce_bandwidth(max_bw, in_rate, in_lanes,
					     out_rate, out_lanes, &new_rate,
					     &new_lanes);
		if (ret) {
			tb_port_info(out, "not enough bandwidth for DP tunnel\n");
			return ret;
		}

		new_bw = tb_dp_bandwidth(new_rate, new_lanes);
		tb_port_dbg(out, "bandwidth reduced to %u Mb/s x%u = %u Mb/s\n",
			    new_rate, new_lanes, new_bw);

		/*
		 * Set new rate and number of lanes before writing it to
		 * the IN port remote caps.
		 */
		out_dp_cap = tb_dp_cap_set_rate(out_dp_cap, new_rate);
		out_dp_cap = tb_dp_cap_set_lanes(out_dp_cap, new_lanes);
	}

	return tb_port_write(in, &out_dp_cap, TB_CFG_PORT,
			     in->cap_adap + DP_REMOTE_CAP, 1);
}