[PATCH 2/4][SRU][U/L/K] thunderbolt: Do not touch CL state configuration during discovery

[Koba Ko]

From: Mika Westerberg <mika.westerberg at linux.intel.com>

BugLink: https://bugs.launchpad.net/bugs/2021949                                 

If the boot firmware has already established tunnels, especially ones
that have special requirements from the link such as DisplayPort, we
should not blindly enable CL states (nor change the TMU configuration).
Otherwise the existing tunnels may not work as expected.

For this reason, skip the CL state enabling when we go over the existing
topology. This will also keep the TMU settings untouched because we do
not change the TMU configuration when CL states are not enabled.

Reported-by: Koba Ko <koba.ko at canonical.com>
Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/7831
Cc: stable at vger.kernel.org # v6.0+
Acked-By: Yehezkel Bernat <YehezkelShB at gmail.com>
Signed-off-by: Mika Westerberg <mika.westerberg at linux.intel.com>
(cherry picked from commit 3fe95742af29b8b4eccab2ba94bc521805c6e10c
git.kernel.org/pub/scm/linux/kernel/git/westeri/thunderbolt.git)
Signed-off-by: Koba Ko <koba.ko at canonical.com>
---
 drivers/thunderbolt/tb.c | 17 ++++++++++++-----
 1 file changed, 12 insertions(+), 5 deletions(-)

diff --git a/drivers/thunderbolt/tb.c b/drivers/thunderbolt/tb.c
index 3f1ab30c4fb15..e1eb092ad1d67 100644
--- a/drivers/thunderbolt/tb.c
+++ b/drivers/thunderbolt/tb.c
@@ -607,6 +607,7 @@ static void tb_scan_port(struct tb_port *port)
 {
 	struct tb_cm *tcm = tb_priv(port->sw->tb);
 	struct tb_port *upstream_port;
+	bool discovery = false;
 	struct tb_switch *sw;
 	int ret;
 
@@ -674,8 +675,10 @@ static void tb_scan_port(struct tb_port *port)
 	 * tunnels and know which switches were authorized already by
 	 * the boot firmware.
 	 */
-	if (!tcm->hotplug_active)
+	if (!tcm->hotplug_active) {
 		dev_set_uevent_suppress(&sw->dev, true);
+		discovery = true;
+	}
 
 	/*
 	 * At the moment Thunderbolt 2 and beyond (devices with LC) we
@@ -705,10 +708,14 @@ static void tb_scan_port(struct tb_port *port)
 	 * CL0s and CL1 are enabled and supported together.
 	 * Silently ignore CLx enabling in case CLx is not supported.
 	 */
-	ret = tb_switch_enable_clx(sw, TB_CL1);
-	if (ret && ret != -EOPNOTSUPP)
-		tb_sw_warn(sw, "failed to enable %s on upstream port\n",
-			   tb_switch_clx_name(TB_CL1));
+	if (discovery) {
+		tb_sw_dbg(sw, "discovery, not touching CL states\n");
+	} else {
+		ret = tb_switch_enable_clx(sw, TB_CL1);
+		if (ret && ret != -EOPNOTSUPP)
+			tb_sw_warn(sw, "failed to enable %s on upstream port\n",
+				   tb_switch_clx_name(TB_CL1));
+	}
 
 	if (tb_switch_is_clx_enabled(sw, TB_CL1))
 		/*
-- 
2.34.1