From 43f977bc60b1cfd3c1d220a9a0a06493fbf3985d Mon Sep 17 00:00:00 2001
From: Gil Fine <gil.fine@intel.com>
Date: Fri, 17 Dec 2021 03:16:43 +0200
Subject: [PATCH] thunderbolt: Enable CL0s for Intel Titan Ridge
References: jsc#SLE-19359
Patch-mainline: v5.17-rc1
Git-commit: 43f977bc60b1cfd3c1d220a9a0a06493fbf3985d

Low power link states (called collectively CLx) are used to reduce
transmitter and receiver power when a high-speed lane is idle. The
simplest one being called CL0s. Follow what we already do for USB4
device routers and enable CL0s for Intel Titan Ridge device router too.
This allows better thermal management.

Signed-off-by: Gil Fine <gil.fine@intel.com>
Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: Oliver Neukum <oneukum@suse.com>
---
 drivers/thunderbolt/lc.c      |  24 +++++
 drivers/thunderbolt/switch.c  | 160 +++++++++++++++++++++++++++++++++-
 drivers/thunderbolt/tb.c      |   7 ++
 drivers/thunderbolt/tb.h      |  16 ++++
 drivers/thunderbolt/tb_regs.h | 102 +++++++++++++++-------
 drivers/thunderbolt/tmu.c     |  53 ++++++++++-
 6 files changed, 324 insertions(+), 38 deletions(-)

diff --git a/drivers/thunderbolt/lc.c b/drivers/thunderbolt/lc.c
index c178f0d7beab..53495a38b4eb 100644
--- a/drivers/thunderbolt/lc.c
+++ b/drivers/thunderbolt/lc.c
@@ -193,6 +193,30 @@ int tb_lc_start_lane_initialization(struct tb_port *port)
 	return tb_sw_write(sw, &ctrl, TB_CFG_SWITCH, cap + TB_LC_SX_CTRL, 1);
 }
 
+/**
+ * tb_lc_is_clx_supported() - Check whether CLx is supported by the lane adapter
+ * @port: Lane adapter
+ *
+ * TB_LC_LINK_ATTR_CPS bit reflects if the link supports CLx including
+ * active cables (if connected on the link).
+ */
+bool tb_lc_is_clx_supported(struct tb_port *port)
+{
+	struct tb_switch *sw = port->sw;
+	int cap, ret;
+	u32 val;
+
+	cap = find_port_lc_cap(port);
+	if (cap < 0)
+		return false;
+
+	ret = tb_sw_read(sw, &val, TB_CFG_SWITCH, cap + TB_LC_LINK_ATTR, 1);
+	if (ret)
+		return false;
+
+	return !!(val & TB_LC_LINK_ATTR_CPS);
+}
+
 static int tb_lc_set_wake_one(struct tb_switch *sw, unsigned int offset,
 			      unsigned int flags)
 {
diff --git a/drivers/thunderbolt/switch.c b/drivers/thunderbolt/switch.c
index c79074f83442..e7dc54d3ea99 100644
--- a/drivers/thunderbolt/switch.c
+++ b/drivers/thunderbolt/switch.c
@@ -2236,6 +2236,10 @@ struct tb_switch *tb_switch_alloc(struct tb *tb, struct device *parent,
 	if (ret > 0)
 		sw->cap_lc = ret;
 
+	ret = tb_switch_find_vse_cap(sw, TB_VSE_CAP_CP_LP);
+	if (ret > 0)
+		sw->cap_lp = ret;
+
 	/* Root switch is always authorized */
 	if (!route)
 		sw->authorized = true;
@@ -3042,6 +3046,13 @@ void tb_switch_suspend(struct tb_switch *sw, bool runtime)
 
 	tb_sw_dbg(sw, "suspending switch\n");
 
+	/*
+	 * Actually only needed for Titan Ridge but for simplicity can be
+	 * done for USB4 device too as CLx is re-enabled at resume.
+	 */
+	if (tb_switch_disable_clx(sw, TB_CL0S))
+		tb_sw_warn(sw, "failed to disable CLx on upstream port\n");
+
 	err = tb_plug_events_active(sw, false);
 	if (err)
 		return;
@@ -3309,6 +3320,7 @@ static int tb_switch_pm_secondary_resolve(struct tb_switch *sw)
 	return tb_port_pm_secondary_disable(down);
 }
 
+/* Called for USB4 or Titan Ridge routers only */
 static bool tb_port_clx_supported(struct tb_port *port, enum tb_clx clx)
 {
 	u32 mask, val;
@@ -3322,8 +3334,12 @@ static bool tb_port_clx_supported(struct tb_port *port, enum tb_clx clx)
 	if (port->xdomain)
 		return false;
 
-	if (!usb4_port_clx_supported(port))
+	if (tb_switch_is_usb4(port->sw)) {
+		if (!usb4_port_clx_supported(port))
+			return false;
+	} else if (!tb_lc_is_clx_supported(port)) {
 		return false;
+	}
 
 	switch (clx) {
 	case TB_CL0S:
@@ -3389,7 +3405,7 @@ static int tb_switch_enable_cl0s(struct tb_switch *sw)
 	struct tb_port *up, *down;
 	int ret;
 
-	if (!tb_switch_is_usb4(sw))
+	if (!tb_switch_is_clx_supported(sw))
 		return 0;
 
 	/*
@@ -3431,6 +3447,13 @@ static int tb_switch_enable_cl0s(struct tb_switch *sw)
 		return ret;
 	}
 
+	ret = tb_switch_mask_clx_objections(sw);
+	if (ret) {
+		tb_port_cl0s_disable(up);
+		tb_port_cl0s_disable(down);
+		return ret;
+	}
+
 	sw->clx = TB_CL0S;
 
 	tb_port_dbg(up, "CL0s enabled\n");
@@ -3477,7 +3500,7 @@ static int tb_switch_disable_cl0s(struct tb_switch *sw)
 	struct tb_port *up, *down;
 	int ret;
 
-	if (!tb_switch_is_usb4(sw))
+	if (!tb_switch_is_clx_supported(sw))
 		return 0;
 
 	/*
@@ -3524,3 +3547,134 @@ int tb_switch_disable_clx(struct tb_switch *sw, enum tb_clx clx)
 		return -EOPNOTSUPP;
 	}
 }
+
+/**
+ * tb_switch_mask_clx_objections() - Mask CLx objections for a router
+ * @sw: Router to mask objections for
+ *
+ * Mask the objections coming from the second depth routers in order to
+ * stop these objections from interfering with the CLx states of the first
+ * depth link.
+ */
+int tb_switch_mask_clx_objections(struct tb_switch *sw)
+{
+	int up_port = sw->config.upstream_port_number;
+	u32 offset, val[2], mask_obj, unmask_obj;
+	int ret, i;
+
+	/* Only Titan Ridge of pre-USB4 devices support CLx states */
+	if (!tb_switch_is_titan_ridge(sw))
+		return 0;
+
+	if (!tb_route(sw))
+		return 0;
+
+	/*
+	 * In Titan Ridge there are only 2 dual-lane Thunderbolt ports:
+	 * Port A consists of lane adapters 1,2 and
+	 * Port B consists of lane adapters 3,4
+	 * If upstream port is A, (lanes are 1,2), we mask objections from
+	 * port B (lanes 3,4) and unmask objections from Port A and vice-versa.
+	 */
+	if (up_port == 1) {
+		mask_obj = TB_LOW_PWR_C0_PORT_B_MASK;
+		unmask_obj = TB_LOW_PWR_C1_PORT_A_MASK;
+		offset = TB_LOW_PWR_C1_CL1;
+	} else {
+		mask_obj = TB_LOW_PWR_C1_PORT_A_MASK;
+		unmask_obj = TB_LOW_PWR_C0_PORT_B_MASK;
+		offset = TB_LOW_PWR_C3_CL1;
+	}
+
+	ret = tb_sw_read(sw, &val, TB_CFG_SWITCH,
+			 sw->cap_lp + offset, ARRAY_SIZE(val));
+	if (ret)
+		return ret;
+
+	for (i = 0; i < ARRAY_SIZE(val); i++) {
+		val[i] |= mask_obj;
+		val[i] &= ~unmask_obj;
+	}
+
+	return tb_sw_write(sw, &val, TB_CFG_SWITCH,
+			   sw->cap_lp + offset, ARRAY_SIZE(val));
+}
+
+/*
+ * Can be used for read/write a specified PCIe bridge for any Thunderbolt 3
+ * device. For now used only for Titan Ridge.
+ */
+static int tb_switch_pcie_bridge_write(struct tb_switch *sw, unsigned int bridge,
+				       unsigned int pcie_offset, u32 value)
+{
+	u32 offset, command, val;
+	int ret;
+
+	if (sw->generation != 3)
+		return -EOPNOTSUPP;
+
+	offset = sw->cap_plug_events + TB_PLUG_EVENTS_PCIE_WR_DATA;
+	ret = tb_sw_write(sw, &value, TB_CFG_SWITCH, offset, 1);
+	if (ret)
+		return ret;
+
+	command = pcie_offset & TB_PLUG_EVENTS_PCIE_CMD_DW_OFFSET_MASK;
+	command |= BIT(bridge + TB_PLUG_EVENTS_PCIE_CMD_BR_SHIFT);
+	command |= TB_PLUG_EVENTS_PCIE_CMD_RD_WR_MASK;
+	command |= TB_PLUG_EVENTS_PCIE_CMD_COMMAND_VAL
+			<< TB_PLUG_EVENTS_PCIE_CMD_COMMAND_SHIFT;
+	command |= TB_PLUG_EVENTS_PCIE_CMD_REQ_ACK_MASK;
+
+	offset = sw->cap_plug_events + TB_PLUG_EVENTS_PCIE_CMD;
+
+	ret = tb_sw_write(sw, &command, TB_CFG_SWITCH, offset, 1);
+	if (ret)
+		return ret;
+
+	ret = tb_switch_wait_for_bit(sw, offset,
+				     TB_PLUG_EVENTS_PCIE_CMD_REQ_ACK_MASK, 0, 100);
+	if (ret)
+		return ret;
+
+	ret = tb_sw_read(sw, &val, TB_CFG_SWITCH, offset, 1);
+	if (ret)
+		return ret;
+
+	if (val & TB_PLUG_EVENTS_PCIE_CMD_TIMEOUT_MASK)
+		return -ETIMEDOUT;
+
+	return 0;
+}
+
+/**
+ * tb_switch_pcie_l1_enable() - Enable PCIe link to enter L1 state
+ * @sw: Router to enable PCIe L1
+ *
+ * For Titan Ridge switch to enter CLx state, its PCIe bridges shall enable
+ * entry to PCIe L1 state. Shall be called after the upstream PCIe tunnel
+ * was configured. Due to Intel platforms limitation, shall be called only
+ * for first hop switch.
+ */
+int tb_switch_pcie_l1_enable(struct tb_switch *sw)
+{
+	struct tb_switch *parent = tb_switch_parent(sw);
+	int ret;
+
+	if (!tb_route(sw))
+		return 0;
+
+	if (!tb_switch_is_titan_ridge(sw))
+		return 0;
+
+	/* Enable PCIe L1 enable only for first hop router (depth = 1) */
+	if (tb_route(parent))
+		return 0;
+
+	/* Write to downstream PCIe bridge #5 aka Dn4 */
+	ret = tb_switch_pcie_bridge_write(sw, 5, 0x143, 0x0c7806b1);
+	if (ret)
+		return ret;
+
+	/* Write to Upstream PCIe bridge #0 aka Up0 */
+	return tb_switch_pcie_bridge_write(sw, 0, 0x143, 0x0c5806b1);
+}
diff --git a/drivers/thunderbolt/tb.c b/drivers/thunderbolt/tb.c
index 1454dc5b6b91..cbd0ad85ffb1 100644
--- a/drivers/thunderbolt/tb.c
+++ b/drivers/thunderbolt/tb.c
@@ -1092,6 +1092,13 @@ static int tb_tunnel_pci(struct tb *tb, struct tb_switch *sw)
 		return -EIO;
 	}
 
+	/*
+	 * PCIe L1 is needed to enable CL0s for Titan Ridge so enable it
+	 * here.
+	 */
+	if (tb_switch_pcie_l1_enable(sw))
+		tb_sw_warn(sw, "failed to enable PCIe L1 for Titan Ridge\n");
+
 	list_add_tail(&tunnel->list, &tcm->tunnel_list);
 	return 0;
 }
diff --git a/drivers/thunderbolt/tb.h b/drivers/thunderbolt/tb.h
index f416e4dcda76..74d3b14f004e 100644
--- a/drivers/thunderbolt/tb.h
+++ b/drivers/thunderbolt/tb.h
@@ -140,6 +140,7 @@ enum tb_clx {
  * @cap_plug_events: Offset to the plug events capability (%0 if not found)
  * @cap_vsec_tmu: Offset to the TMU vendor specific capability (%0 if not found)
  * @cap_lc: Offset to the link controller capability (%0 if not found)
+ * @cap_lp: Offset to the low power (CLx for TBT) capability (%0 if not found)
  * @is_unplugged: The switch is going away
  * @drom: DROM of the switch (%NULL if not found)
  * @nvm: Pointer to the NVM if the switch has one (%NULL otherwise)
@@ -192,6 +193,7 @@ struct tb_switch {
 	int cap_plug_events;
 	int cap_vsec_tmu;
 	int cap_lc;
+	int cap_lp;
 	bool is_unplugged;
 	u8 *drom;
 	struct tb_nvm *nvm;
@@ -972,6 +974,19 @@ static inline bool tb_switch_is_cl0s_enabled(const struct tb_switch *sw)
 	return sw->clx == TB_CL0S;
 }
 
+/**
+ * tb_switch_is_clx_supported() - Is CLx supported on this type of router
+ * @sw: The router to check CLx support for
+ */
+static inline bool tb_switch_is_clx_supported(const struct tb_switch *sw)
+{
+	return tb_switch_is_usb4(sw) || tb_switch_is_titan_ridge(sw);
+}
+
+int tb_switch_mask_clx_objections(struct tb_switch *sw);
+
+int tb_switch_pcie_l1_enable(struct tb_switch *sw);
+
 int tb_wait_for_port(struct tb_port *port, bool wait_if_unplugged);
 int tb_port_add_nfc_credits(struct tb_port *port, int credits);
 int tb_port_clear_counter(struct tb_port *port, int counter);
@@ -1065,6 +1080,7 @@ void tb_lc_unconfigure_port(struct tb_port *port);
 int tb_lc_configure_xdomain(struct tb_port *port);
 void tb_lc_unconfigure_xdomain(struct tb_port *port);
 int tb_lc_start_lane_initialization(struct tb_port *port);
+bool tb_lc_is_clx_supported(struct tb_port *port);
 int tb_lc_set_wake(struct tb_switch *sw, unsigned int flags);
 int tb_lc_set_sleep(struct tb_switch *sw);
 bool tb_lc_lane_bonding_possible(struct tb_switch *sw);
diff --git a/drivers/thunderbolt/tb_regs.h b/drivers/thunderbolt/tb_regs.h
index 105118ecc9cd..a74f4878d3e7 100644
--- a/drivers/thunderbolt/tb_regs.h
+++ b/drivers/thunderbolt/tb_regs.h
@@ -447,42 +447,78 @@ struct tb_regs_hop {
 } __packed;
 
 /* TMU Thunderbolt 3 registers */
-#define TB_TIME_VSEC_3_CS_26		0x1a
-#define TB_TIME_VSEC_3_CS_26_TD		BIT(22)
+#define TB_TIME_VSEC_3_CS_9			0x9
+#define TB_TIME_VSEC_3_CS_9_TMU_OBJ_MASK	GENMASK(17, 16)
+#define TB_TIME_VSEC_3_CS_26			0x1a
+#define TB_TIME_VSEC_3_CS_26_TD			BIT(22)
+
+/*
+ * Used for Titan Ridge only. Bits are part of the same register: TMU_ADP_CS_6
+ * (see above) as in USB4 spec, but these specific bits used for Titan Ridge
+ * only and reserved in USB4 spec.
+ */
+#define TMU_ADP_CS_6_DISABLE_TMU_OBJ_MASK	GENMASK(3, 2)
+#define TMU_ADP_CS_6_DISABLE_TMU_OBJ_CL1	BIT(2)
+#define TMU_ADP_CS_6_DISABLE_TMU_OBJ_CL2	BIT(3)
+
+/* Plug Events registers */
+#define TB_PLUG_EVENTS_PCIE_WR_DATA		0x1b
+#define TB_PLUG_EVENTS_PCIE_CMD			0x1c
+#define TB_PLUG_EVENTS_PCIE_CMD_DW_OFFSET_MASK	GENMASK(9, 0)
+#define TB_PLUG_EVENTS_PCIE_CMD_BR_SHIFT	10
+#define TB_PLUG_EVENTS_PCIE_CMD_BR_MASK		GENMASK(17, 10)
+#define TB_PLUG_EVENTS_PCIE_CMD_RD_WR_MASK	BIT(21)
+#define TB_PLUG_EVENTS_PCIE_CMD_WR		0x1
+#define TB_PLUG_EVENTS_PCIE_CMD_COMMAND_SHIFT	22
+#define TB_PLUG_EVENTS_PCIE_CMD_COMMAND_MASK	GENMASK(24, 22)
+#define TB_PLUG_EVENTS_PCIE_CMD_COMMAND_VAL	0x2
+#define TB_PLUG_EVENTS_PCIE_CMD_REQ_ACK_MASK	BIT(30)
+#define TB_PLUG_EVENTS_PCIE_CMD_TIMEOUT_MASK	BIT(31)
+#define TB_PLUG_EVENTS_PCIE_CMD_RD_DATA		0x1d
+
+/* CP Low Power registers */
+#define TB_LOW_PWR_C1_CL1			0x1
+#define TB_LOW_PWR_C1_CL1_OBJ_MASK		GENMASK(4, 1)
+#define TB_LOW_PWR_C1_CL2_OBJ_MASK		GENMASK(4, 1)
+#define TB_LOW_PWR_C1_PORT_A_MASK		GENMASK(2, 1)
+#define TB_LOW_PWR_C0_PORT_B_MASK		GENMASK(4, 3)
+#define TB_LOW_PWR_C3_CL1			0x3
 
 /* Common link controller registers */
-#define TB_LC_DESC			0x02
-#define TB_LC_DESC_NLC_MASK		GENMASK(3, 0)
-#define TB_LC_DESC_SIZE_SHIFT		8
-#define TB_LC_DESC_SIZE_MASK		GENMASK(15, 8)
-#define TB_LC_DESC_PORT_SIZE_SHIFT	16
-#define TB_LC_DESC_PORT_SIZE_MASK	GENMASK(27, 16)
-#define TB_LC_FUSE			0x03
-#define TB_LC_SNK_ALLOCATION		0x10
-#define TB_LC_SNK_ALLOCATION_SNK0_MASK	GENMASK(3, 0)
-#define TB_LC_SNK_ALLOCATION_SNK0_CM	0x1
-#define TB_LC_SNK_ALLOCATION_SNK1_SHIFT	4
-#define TB_LC_SNK_ALLOCATION_SNK1_MASK	GENMASK(7, 4)
-#define TB_LC_SNK_ALLOCATION_SNK1_CM	0x1
-#define TB_LC_POWER			0x740
+#define TB_LC_DESC				0x02
+#define TB_LC_DESC_NLC_MASK			GENMASK(3, 0)
+#define TB_LC_DESC_SIZE_SHIFT			8
+#define TB_LC_DESC_SIZE_MASK			GENMASK(15, 8)
+#define TB_LC_DESC_PORT_SIZE_SHIFT		16
+#define TB_LC_DESC_PORT_SIZE_MASK		GENMASK(27, 16)
+#define TB_LC_FUSE				0x03
+#define TB_LC_SNK_ALLOCATION			0x10
+#define TB_LC_SNK_ALLOCATION_SNK0_MASK		GENMASK(3, 0)
+#define TB_LC_SNK_ALLOCATION_SNK0_CM		0x1
+#define TB_LC_SNK_ALLOCATION_SNK1_SHIFT		4
+#define TB_LC_SNK_ALLOCATION_SNK1_MASK		GENMASK(7, 4)
+#define TB_LC_SNK_ALLOCATION_SNK1_CM		0x1
+#define TB_LC_POWER				0x740
 
 /* Link controller registers */
-#define TB_LC_PORT_ATTR			0x8d
-#define TB_LC_PORT_ATTR_BE		BIT(12)
-
-#define TB_LC_SX_CTRL			0x96
-#define TB_LC_SX_CTRL_WOC		BIT(1)
-#define TB_LC_SX_CTRL_WOD		BIT(2)
-#define TB_LC_SX_CTRL_WODPC		BIT(3)
-#define TB_LC_SX_CTRL_WODPD		BIT(4)
-#define TB_LC_SX_CTRL_WOU4		BIT(5)
-#define TB_LC_SX_CTRL_WOP		BIT(6)
-#define TB_LC_SX_CTRL_L1C		BIT(16)
-#define TB_LC_SX_CTRL_L1D		BIT(17)
-#define TB_LC_SX_CTRL_L2C		BIT(20)
-#define TB_LC_SX_CTRL_L2D		BIT(21)
-#define TB_LC_SX_CTRL_SLI		BIT(29)
-#define TB_LC_SX_CTRL_UPSTREAM		BIT(30)
-#define TB_LC_SX_CTRL_SLP		BIT(31)
+#define TB_LC_PORT_ATTR				0x8d
+#define TB_LC_PORT_ATTR_BE			BIT(12)
+
+#define TB_LC_SX_CTRL				0x96
+#define TB_LC_SX_CTRL_WOC			BIT(1)
+#define TB_LC_SX_CTRL_WOD			BIT(2)
+#define TB_LC_SX_CTRL_WODPC			BIT(3)
+#define TB_LC_SX_CTRL_WODPD			BIT(4)
+#define TB_LC_SX_CTRL_WOU4			BIT(5)
+#define TB_LC_SX_CTRL_WOP			BIT(6)
+#define TB_LC_SX_CTRL_L1C			BIT(16)
+#define TB_LC_SX_CTRL_L1D			BIT(17)
+#define TB_LC_SX_CTRL_L2C			BIT(20)
+#define TB_LC_SX_CTRL_L2D			BIT(21)
+#define TB_LC_SX_CTRL_SLI			BIT(29)
+#define TB_LC_SX_CTRL_UPSTREAM			BIT(30)
+#define TB_LC_SX_CTRL_SLP			BIT(31)
+#define TB_LC_LINK_ATTR				0x97
+#define TB_LC_LINK_ATTR_CPS			BIT(18)
 
 #endif
diff --git a/drivers/thunderbolt/tmu.c b/drivers/thunderbolt/tmu.c
index 8392d1352c98..e4a07a26f693 100644
--- a/drivers/thunderbolt/tmu.c
+++ b/drivers/thunderbolt/tmu.c
@@ -334,7 +334,12 @@ int tb_switch_tmu_post_time(struct tb_switch *sw)
  */
 int tb_switch_tmu_disable(struct tb_switch *sw)
 {
-	if (!tb_switch_is_usb4(sw))
+	/*
+	 * No need to disable TMU on devices that don't support CLx since
+	 * on these devices e.g. Alpine Ridge and earlier, the TMU mode
+	 * HiFi bi-directional is enabled by default and we don't change it.
+	 */
+	if (!tb_switch_is_clx_supported(sw))
 		return 0;
 
 	/* Already disabled? */
@@ -450,6 +455,31 @@ static int __tb_switch_tmu_enable_bidirectional(struct tb_switch *sw)
 	return ret;
 }
 
+static int tb_switch_tmu_objection_mask(struct tb_switch *sw)
+{
+	u32 val;
+	int ret;
+
+	ret = tb_sw_read(sw, &val, TB_CFG_SWITCH,
+			 sw->cap_vsec_tmu + TB_TIME_VSEC_3_CS_9, 1);
+	if (ret)
+		return ret;
+
+	val &= ~TB_TIME_VSEC_3_CS_9_TMU_OBJ_MASK;
+
+	return tb_sw_write(sw, &val, TB_CFG_SWITCH,
+			   sw->cap_vsec_tmu + TB_TIME_VSEC_3_CS_9, 1);
+}
+
+static int tb_switch_tmu_unidirectional_enable(struct tb_switch *sw)
+{
+	struct tb_port *up = tb_upstream_port(sw);
+
+	return tb_port_tmu_write(up, TMU_ADP_CS_6,
+				 TMU_ADP_CS_6_DISABLE_TMU_OBJ_MASK,
+				 TMU_ADP_CS_6_DISABLE_TMU_OBJ_MASK);
+}
+
 /*
  * This function is called when the previous TMU mode was
  * TB_SWITCH_TMU_RATE_OFF.
@@ -497,12 +527,31 @@ static int tb_switch_tmu_hifi_enable(struct tb_switch *sw)
 	if (unidirectional && !sw->tmu.has_ucap)
 		return -EOPNOTSUPP;
 
-	if (!tb_switch_is_usb4(sw))
+	/*
+	 * No need to enable TMU on devices that don't support CLx since on
+	 * these devices e.g. Alpine Ridge and earlier, the TMU mode HiFi
+	 * bi-directional is enabled by default.
+	 */
+	if (!tb_switch_is_clx_supported(sw))
 		return 0;
 
 	if (tb_switch_tmu_hifi_is_enabled(sw, sw->tmu.unidirectional_request))
 		return 0;
 
+	if (tb_switch_is_titan_ridge(sw) && unidirectional) {
+		/* Titan Ridge supports only CL0s */
+		if (!tb_switch_is_cl0s_enabled(sw))
+			return -EOPNOTSUPP;
+
+		ret = tb_switch_tmu_objection_mask(sw);
+		if (ret)
+			return ret;
+
+		ret = tb_switch_tmu_unidirectional_enable(sw);
+		if (ret)
+			return ret;
+	}
+
 	ret = tb_switch_tmu_set_time_disruption(sw, true);
 	if (ret)
 		return ret;
-- 
2.26.2

