thunderbolt: Add module parameter for CLx disabling

Add a module parameter that allows user to completely disable CLx
functionality in case problems are found.

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

drivers/thunderbolt/switch.c

@@ -13,6 +13,7 @@
 #include <linux/sched/signal.h>
 #include <linux/sizes.h>
 #include <linux/slab.h>
+#include <linux/module.h>
 
 #include "tb.h"
 
@@ -26,6 +27,10 @@ struct nvm_auth_status {
 	u32 status;
 };
 
+static bool clx_enabled = true;
+module_param_named(clx, clx_enabled, bool, 0444);
+MODULE_PARM_DESC(clx, "allow low power states on the high-speed lanes (default: true)");
+
 /*
  * Hold NVM authentication failure status per switch This information
  * needs to stay around even when the switch gets power cycled so we
@@ -3478,6 +3483,9 @@ int tb_switch_enable_clx(struct tb_switch *sw, enum tb_clx clx)
 {
 	struct tb_switch *root_sw = sw->tb->root_switch;
 
+	if (!clx_enabled)
+		return 0;
+
 	/*
 	 * CLx is not enabled and validated on Intel USB4 platforms before
 	 * Alder Lake.
@@ -3539,6 +3547,9 @@ static int tb_switch_disable_cl0s(struct tb_switch *sw)
  */
 int tb_switch_disable_clx(struct tb_switch *sw, enum tb_clx clx)
 {
+	if (!clx_enabled)
+		return 0;
+
 	switch (clx) {
 	case TB_CL0S:
 		return tb_switch_disable_cl0s(sw);