From 3c052ec6f4f866163573445a02d60b629805a6e7 Mon Sep 17 00:00:00 2001
From: Gil Fine <gil.fine@linux.intel.com>
Date: Wed, 15 Nov 2023 12:09:53 +0200
Subject: [PATCH] thunderbolt: Transition link to asymmetric only when both
 sides support it
Git-commit: 3c052ec6f4f866163573445a02d60b629805a6e7
References: jsc#PED-6054
Patch-mainline: v6.8-rc1

We can transition Gen 4 link to asymmetric only when both sides of the
link support it in the required direction. For this reason make sure
that the downstream adapter also supports asymmetric link before
starting the transition.

Signed-off-by: Gil Fine <gil.fine@linux.intel.com>
Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: Oliver Neukum <oneukum@suse.com>

---
 drivers/thunderbolt/tb.c | 16 ++++++++++------
 1 file changed, 10 insertions(+), 6 deletions(-)

diff --git a/drivers/thunderbolt/tb.c b/drivers/thunderbolt/tb.c
index 6ff3e9624301..f81e7cf53d69 100644
--- a/drivers/thunderbolt/tb.c
+++ b/drivers/thunderbolt/tb.c
@@ -1094,8 +1094,9 @@ static int tb_configure_asym(struct tb *tb, struct tb_port *src_port,
 	clx = tb_disable_clx(sw);
 
 	tb_for_each_upstream_port_on_path(src_port, dst_port, up) {
+		struct tb_port *down = tb_switch_downstream_port(up->sw);
+		enum tb_link_width width_up, width_down;
 		int consumed_up, consumed_down;
-		enum tb_link_width width;
 
 		ret = tb_consumed_dp_bandwidth(tb, src_port, dst_port, up,
 					       &consumed_up, &consumed_down);
@@ -1116,7 +1117,8 @@ static int tb_configure_asym(struct tb *tb, struct tb_port *src_port,
 			if (consumed_down + requested_down < asym_threshold)
 				continue;
 
-			width = TB_LINK_WIDTH_ASYM_RX;
+			width_up = TB_LINK_WIDTH_ASYM_RX;
+			width_down = TB_LINK_WIDTH_ASYM_TX;
 		} else {
 			/* Upstream, the opposite of above */
 			if (consumed_down + requested_down >= TB_ASYM_MIN) {
@@ -1126,13 +1128,15 @@ static int tb_configure_asym(struct tb *tb, struct tb_port *src_port,
 			if (consumed_up + requested_up < asym_threshold)
 				continue;
 
-			width = TB_LINK_WIDTH_ASYM_TX;
+			width_up = TB_LINK_WIDTH_ASYM_TX;
+			width_down = TB_LINK_WIDTH_ASYM_RX;
 		}
 
-		if (up->sw->link_width == width)
+		if (up->sw->link_width == width_up)
 			continue;
 
-		if (!tb_port_width_supported(up, width))
+		if (!tb_port_width_supported(up, width_up) ||
+		    !tb_port_width_supported(down, width_down))
 			continue;
 
 		tb_sw_dbg(up->sw, "configuring asymmetric link\n");
@@ -1141,7 +1145,7 @@ static int tb_configure_asym(struct tb *tb, struct tb_port *src_port,
 		 * Here requested + consumed > threshold so we need to
 		 * transtion the link into asymmetric now.
 		 */
-		ret = tb_switch_set_link_width(up->sw, width);
+		ret = tb_switch_set_link_width(up->sw, width_up);
 		if (ret) {
 			tb_sw_warn(up->sw, "failed to set link width\n");
 			break;
-- 
2.43.0