linux-kernel - Re: Apple Thunderbolt Display chaining

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Date:   Wed, 30 Mar 2022 17:47:27 +0300
From:   Mika Westerberg <mika.westerberg@...ux.intel.com>
To:     Brad Campbell <lists2009@...rfbargle.com>
Cc:     linux-kernel@...r.kernel.org
Subject: Re: Apple Thunderbolt Display chaining

Hi,

On Wed, Mar 30, 2022 at 10:24:35PM +0800, Brad Campbell wrote:
> Nope, that did the same thing. I wonder though. I'm testing it on the laptop and that reports :
> [    0.442832] thunderbolt 0000:07:00.0:  Thunderbolt 2 Switch: 8086:156d (Revision: 0, TB Version: 2)
> 
> Changing "if (in->sw->generation == 1)" to "if (in->sw->generation == 2)" on the laptop solves that.

Heh, indeed I forgot that this is Falcon Ridge.

> I can't test hotplug properly on the iMac due to the radeon training issue.
> 
> The laptop still has the issue of a cold boot working in one socket
> and not the other, but hot plug is working correctly.

Let's try this one next:

diff --git a/drivers/thunderbolt/tunnel.c b/drivers/thunderbolt/tunnel.c
index a473cc7d9a8d..7150b5bc5403 100644
--- a/drivers/thunderbolt/tunnel.c
+++ b/drivers/thunderbolt/tunnel.c
@@ -865,6 +865,8 @@ struct tb_tunnel *tb_tunnel_alloc_dp(struct tb *tb, struct tb_port *in,
 	struct tb_tunnel *tunnel;
 	struct tb_path **paths;
 	struct tb_path *path;
+	struct tb_port *port;
+	int link_nr;
 
 	if (WARN_ON(!in->cap_adap || !out->cap_adap))
 		return NULL;
@@ -883,22 +885,34 @@ struct tb_tunnel *tb_tunnel_alloc_dp(struct tb *tb, struct tb_port *in,
 
 	paths = tunnel->paths;
 
+	/*
+	 * Hard code the lane for both DP IN adapters when first
+	 * generation hardware is present in the topology.
+	 */
+	link_nr = 1;
+	tb_for_each_port_on_path(in, out, port) {
+		if (tb_port_is_null(port) && port->sw->generation == 1) {
+			link_nr = in->port == 11 ? 1 : 0;
+			break;
+		}
+	}
+
 	path = tb_path_alloc(tb, in, TB_DP_VIDEO_HOPID, out, TB_DP_VIDEO_HOPID,
-			     1, "Video");
+			     link_nr, "Video");
 	if (!path)
 		goto err_free;
 	tb_dp_init_video_path(path);
 	paths[TB_DP_VIDEO_PATH_OUT] = path;
 
 	path = tb_path_alloc(tb, in, TB_DP_AUX_TX_HOPID, out,
-			     TB_DP_AUX_TX_HOPID, 1, "AUX TX");
+			     TB_DP_AUX_TX_HOPID, link_nr, "AUX TX");
 	if (!path)
 		goto err_free;
 	tb_dp_init_aux_path(path);
 	paths[TB_DP_AUX_PATH_OUT] = path;
 
 	path = tb_path_alloc(tb, out, TB_DP_AUX_RX_HOPID, in,
-			     TB_DP_AUX_RX_HOPID, 1, "AUX RX");
+			     TB_DP_AUX_RX_HOPID, link_nr, "AUX RX");
 	if (!path)
 		goto err_free;
 	tb_dp_init_aux_path(path);