linux-kernel - [PATCH 6.6 14/14] thunderbolt: Improve DisplayPort tunnel setup process to be more robust

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Message-Id: <20241001173109.1513-15-alexandru.gagniuc@hp.com>
Date: Tue,  1 Oct 2024 17:31:09 +0000
From: Alexandru Gagniuc <alexandru.gagniuc@...com>
To: gregkh@...uxfoundation.org,
	stable@...r.kernel.org
Cc: qin.wan@...com,
	andreas.noever@...il.com,
	michael.jamet@...el.com,
	mika.westerberg@...ux.intel.com,
	YehezkelShB@...il.com,
	linux-usb@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Gil Fine <gil.fine@...ux.intel.com>,
	Alexandru Gagniuc <alexandru.gagniuc@...com>
Subject: [PATCH 6.6 14/14] thunderbolt: Improve DisplayPort tunnel setup process to be more robust

From: Gil Fine <gil.fine@...ux.intel.com>

[ Upstream commit b4734507ac55cc7ea1380e20e83f60fcd7031955 ]

After DisplayPort tunnel setup, we add verification that the DPRX
capabilities read process completed. Otherwise, we bail out, teardown
the tunnel, and try setup another DisplayPort tunnel using next
available DP IN adapter. We do so till all DP IN adapters tried. This
way, we avoid allocating DP IN adapter and (bandwidth for it) for
unusable tunnel.

Signed-off-by: Gil Fine <gil.fine@...ux.intel.com>
Signed-off-by: Mika Westerberg <mika.westerberg@...ux.intel.com>
Signed-off-by: Qin Wan <qin.wan@...com>
Signed-off-by: Alexandru Gagniuc <alexandru.gagniuc@...com>
---
 drivers/thunderbolt/tb.c | 84 ++++++++++++++++++++--------------------
 1 file changed, 43 insertions(+), 41 deletions(-)

diff --git a/drivers/thunderbolt/tb.c b/drivers/thunderbolt/tb.c
index c52cbd5194f1..ea155547e871 100644
--- a/drivers/thunderbolt/tb.c
+++ b/drivers/thunderbolt/tb.c
@@ -1699,48 +1699,14 @@ static struct tb_port *tb_find_dp_out(struct tb *tb, struct tb_port *in)
 	return NULL;
 }
 
-static bool tb_tunnel_one_dp(struct tb *tb)
+static bool tb_tunnel_one_dp(struct tb *tb, struct tb_port *in,
+			     struct tb_port *out)
 {
 	int available_up, available_down, ret, link_nr;
 	struct tb_cm *tcm = tb_priv(tb);
-	struct tb_port *port, *in, *out;
 	int consumed_up, consumed_down;
 	struct tb_tunnel *tunnel;
 
-	/*
-	 * Find pair of inactive DP IN and DP OUT adapters and then
-	 * establish a DP tunnel between them.
-	 */
-	tb_dbg(tb, "looking for DP IN <-> DP OUT pairs:\n");
-
-	in = NULL;
-	out = NULL;
-	list_for_each_entry(port, &tcm->dp_resources, list) {
-		if (!tb_port_is_dpin(port))
-			continue;
-
-		if (tb_port_is_enabled(port)) {
-			tb_port_dbg(port, "DP IN in use\n");
-			continue;
-		}
-
-		in = port;
-		tb_port_dbg(in, "DP IN available\n");
-
-		out = tb_find_dp_out(tb, port);
-		if (out)
-			break;
-	}
-
-	if (!in) {
-		tb_dbg(tb, "no suitable DP IN adapter available, not tunneling\n");
-		return false;
-	}
-	if (!out) {
-		tb_dbg(tb, "no suitable DP OUT adapter available, not tunneling\n");
-		return false;
-	}
-
 	/*
 	 * This is only applicable to links that are not bonded (so
 	 * when Thunderbolt 1 hardware is involved somewhere in the
@@ -1801,15 +1767,19 @@ static bool tb_tunnel_one_dp(struct tb *tb)
 		goto err_free;
 	}
 
+	/* If fail reading tunnel's consumed bandwidth, tear it down */
+	ret = tb_tunnel_consumed_bandwidth(tunnel, &consumed_up, &consumed_down);
+	if (ret)
+		goto err_deactivate;
+
 	list_add_tail(&tunnel->list, &tcm->tunnel_list);
-	tb_reclaim_usb3_bandwidth(tb, in, out);
 
+	tb_reclaim_usb3_bandwidth(tb, in, out);
 	/*
 	 * Transition the links to asymmetric if the consumption exceeds
 	 * the threshold.
 	 */
-	if (!tb_tunnel_consumed_bandwidth(tunnel, &consumed_up, &consumed_down))
-		tb_configure_asym(tb, in, out, consumed_up, consumed_down);
+	tb_configure_asym(tb, in, out, consumed_up, consumed_down);
 
 	/* Update the domain with the new bandwidth estimation */
 	tb_recalc_estimated_bandwidth(tb);
@@ -1821,6 +1791,8 @@ static bool tb_tunnel_one_dp(struct tb *tb)
 	tb_increase_tmu_accuracy(tunnel);
 	return true;
 
+err_deactivate:
+	tb_tunnel_deactivate(tunnel);
 err_free:
 	tb_tunnel_free(tunnel);
 err_reclaim_usb:
@@ -1840,13 +1812,43 @@ static bool tb_tunnel_one_dp(struct tb *tb)
 
 static void tb_tunnel_dp(struct tb *tb)
 {
+	struct tb_cm *tcm = tb_priv(tb);
+	struct tb_port *port, *in, *out;
+
 	if (!tb_acpi_may_tunnel_dp()) {
 		tb_dbg(tb, "DP tunneling disabled, not creating tunnel\n");
 		return;
 	}
 
-	while (tb_tunnel_one_dp(tb))
-		;
+	/*
+	 * Find pair of inactive DP IN and DP OUT adapters and then
+	 * establish a DP tunnel between them.
+	 */
+	tb_dbg(tb, "looking for DP IN <-> DP OUT pairs:\n");
+
+	in = NULL;
+	out = NULL;
+	list_for_each_entry(port, &tcm->dp_resources, list) {
+		if (!tb_port_is_dpin(port))
+			continue;
+
+		if (tb_port_is_enabled(port)) {
+			tb_port_dbg(port, "DP IN in use\n");
+			continue;
+		}
+
+		in = port;
+		tb_port_dbg(in, "DP IN available\n");
+
+		out = tb_find_dp_out(tb, port);
+		if (out)
+			tb_tunnel_one_dp(tb, in, out);
+		else
+			tb_port_dbg(in, "no suitable DP OUT adapter available, not tunneling\n");
+	}
+
+	if (!in)
+		tb_dbg(tb, "no suitable DP IN adapter available, not tunneling\n");
 }
 
 static void tb_enter_redrive(struct tb_port *port)
-- 
2.45.1