thunderbolt: Add TMU uni-directional mode

Up until Titan Ridge (Thunderbolt 3) device routers only supported
bi-directional mode. In this patch we add to TMU a uni-directional mode.
The uni-directional mode is needed for enabling of low power state of
the link (CLx).

Signed-off-by: Gil Fine <[e-mail]>
Signed-off-by: Mika Westerberg <[e-mail]>

drivers/thunderbolt/tb.c

···
 	int ret;
 
 	/* If it is already enabled in correct mode, don't touch it */
-	if (tb_switch_tmu_is_enabled(sw))
+	if (tb_switch_tmu_hifi_is_enabled(sw, sw->tmu.unidirectional_request))
 		return 0;
 
 	ret = tb_switch_tmu_disable(sw);
···
 	tb_switch_lane_bonding_enable(sw);
 	/* Set the link configured */
 	tb_switch_configure_link(sw);
+	tb_switch_tmu_configure(sw, TB_SWITCH_TMU_RATE_HIFI, false);
 
 	if (tb_enable_tmu(sw))
 		tb_sw_warn(sw, "failed to enable TMU\n");
···
 		return ret;
 	}
 
+	tb_switch_tmu_configure(tb->root_switch, TB_SWITCH_TMU_RATE_HIFI, false);
 	/* Enable TMU if it is off */
 	tb_switch_tmu_enable(tb->root_switch);
 	/* Full scan to discover devices added before the driver was loaded. */
···
 	if (sw->is_unplugged)
 		return;
 
+	/*
+	 * tb_switch_tmu_configure() was already called when the switch was
+	 * added before entering system sleep or runtime suspend,
+	 * so no need to call it again before enabling TMU.
+	 */
 	if (tb_enable_tmu(sw))
 		tb_sw_warn(sw, "failed to restore TMU configuration\n");
 

drivers/thunderbolt/tb.h

···
  * @cap: Offset to the TMU capability (%0 if not found)
  * @has_ucap: Does the switch support uni-directional mode
  * @rate: TMU refresh rate related to upstream switch. In case of root
- *	  switch this holds the domain rate.
+ *	  switch this holds the domain rate. Reflects the HW setting.
  * @unidirectional: Is the TMU in uni-directional or bi-directional mode
- *		    related to upstream switch. Don't case for root switch.
+ *		    related to upstream switch. Don't care for root switch.
+ *		    Reflects the HW setting.
+ * @unidirectional_request: Is the new TMU mode: uni-directional or bi-directional
+ *			    that is requested to be set. Related to upstream switch.
+ *			    Don't care for root switch.
+ * @rate_request: TMU new refresh rate related to upstream switch that is
+ *		  requested to be set. In case of root switch, this holds
+ *		  the new domain rate that is requested to be set.
  */
 struct tb_switch_tmu {
 	int cap;
 	bool has_ucap;
 	enum tb_switch_tmu_rate rate;
 	bool unidirectional;
+	bool unidirectional_request;
+	enum tb_switch_tmu_rate rate_request;
 };
 
 /**
···
 int tb_switch_tmu_post_time(struct tb_switch *sw);
 int tb_switch_tmu_disable(struct tb_switch *sw);
 int tb_switch_tmu_enable(struct tb_switch *sw);
-
-static inline bool tb_switch_tmu_is_enabled(const struct tb_switch *sw)
+void tb_switch_tmu_configure(struct tb_switch *sw,
+			     enum tb_switch_tmu_rate rate,
+			     bool unidirectional);
+/**
+ * tb_switch_tmu_hifi_is_enabled() - Checks if the specified TMU mode is enabled
+ * @sw: Router whose TMU mode to check
+ * @unidirectional: If uni-directional (bi-directional otherwise)
+ *
+ * Return true if hardware TMU configuration matches the one passed in
+ * as parameter. That is HiFi and either uni-directional or bi-directional.
+ */
+static inline bool tb_switch_tmu_hifi_is_enabled(const struct tb_switch *sw,
+						 bool unidirectional)
 {
 	return sw->tmu.rate == TB_SWITCH_TMU_RATE_HIFI &&
-	       !sw->tmu.unidirectional;
+	       sw->tmu.unidirectional == unidirectional;
 }
 
 int tb_wait_for_port(struct tb_port *port, bool wait_if_unplugged);

drivers/thunderbolt/tb_regs.h

···
 #define TMU_RTR_CS_3_TS_PACKET_INTERVAL_SHIFT	16
 #define TMU_RTR_CS_22				0x16
 #define TMU_RTR_CS_24				0x18
+#define TMU_RTR_CS_25				0x19
 
 enum tb_port_type {
 	TB_TYPE_INACTIVE	= 0x000000,
···
 /* TMU adapter registers */
 #define TMU_ADP_CS_3				0x03
 #define TMU_ADP_CS_3_UDM			BIT(29)
+#define TMU_ADP_CS_6				0x06
+#define TMU_ADP_CS_6_DTS			BIT(1)
 
 /* Lane adapter registers */
 #define LANE_ADP_CS_0				0x00

drivers/thunderbolt/tmu.c

···
 	return tb_port_tmu_set_unidirectional(port, false);
 }
 
+static inline int tb_port_tmu_unidirectional_enable(struct tb_port *port)
+{
+	return tb_port_tmu_set_unidirectional(port, true);
+}
+
 static bool tb_port_tmu_is_unidirectional(struct tb_port *port)
 {
 	int ret;
···
 		return false;
 
 	return val & TMU_ADP_CS_3_UDM;
+}
+
+static int tb_port_tmu_time_sync(struct tb_port *port, bool time_sync)
+{
+	u32 val = time_sync ? TMU_ADP_CS_6_DTS : 0;
+
+	return tb_port_tmu_write(port, TMU_ADP_CS_6, TMU_ADP_CS_6_DTS, val);
+}
+
+static int tb_port_tmu_time_sync_disable(struct tb_port *port)
+{
+	return tb_port_tmu_time_sync(port, true);
+}
+
+static int tb_port_tmu_time_sync_enable(struct tb_port *port)
+{
+	return tb_port_tmu_time_sync(port, false);
 }
 
 static int tb_switch_tmu_set_time_disruption(struct tb_switch *sw, bool set)
···
  */
 int tb_switch_tmu_post_time(struct tb_switch *sw)
 {
-	unsigned int  post_local_time_offset, post_time_offset;
+	unsigned int post_time_high_offset, post_time_high = 0;
+	unsigned int post_local_time_offset, post_time_offset;
 	struct tb_switch *root_switch = sw->tb->root_switch;
 	u64 hi, mid, lo, local_time, post_time;
 	int i, ret, retries = 100;
···
 
 	post_local_time_offset = sw->tmu.cap + TMU_RTR_CS_22;
 	post_time_offset = sw->tmu.cap + TMU_RTR_CS_24;
+	post_time_high_offset = sw->tmu.cap + TMU_RTR_CS_25;
 
 	/*
 	 * Write the Grandmaster time to the Post Local Time registers
···
 		goto out;
 
 	/*
-	 * Have the new switch update its local time (by writing 1 to
-	 * the post_time registers) and wait for the completion of the
-	 * same (post_time register becomes 0). This means the time has
-	 * been converged properly.
+	 * Have the new switch update its local time by:
+	 * 1) writing 0x1 to the Post Time Low register and 0xffffffff to
+	 * Post Time High register.
+	 * 2) write 0 to Post Time High register and then wait for
+	 * the completion of the post_time register becomes 0.
+	 * This means the time has been converged properly.
 	 */
-	post_time = 1;
+	post_time = 0xffffffff00000001ULL;
 
 	ret = tb_sw_write(sw, &post_time, TB_CFG_SWITCH, post_time_offset, 2);
+	if (ret)
+		goto out;
+
+	ret = tb_sw_write(sw, &post_time_high, TB_CFG_SWITCH,
+			  post_time_high_offset, 1);
 	if (ret)
 		goto out;
 
···
  */
 int tb_switch_tmu_disable(struct tb_switch *sw)
 {
-	int ret;
-
 	if (!tb_switch_is_usb4(sw))
 		return 0;
 
···
 	if (sw->tmu.rate == TB_SWITCH_TMU_RATE_OFF)
 		return 0;
 
-	if (sw->tmu.unidirectional) {
+
+	if (tb_route(sw)) {
+		bool unidirectional = tb_switch_tmu_hifi_is_enabled(sw, true);
 		struct tb_switch *parent = tb_switch_parent(sw);
-		struct tb_port *up, *down;
+		struct tb_port *down, *up;
+		int ret;
 
-		up = tb_upstream_port(sw);
 		down = tb_port_at(tb_route(sw), parent);
+		up = tb_upstream_port(sw);
+		/*
+		 * In case of uni-directional time sync, TMU handshake is
+		 * initiated by upstream router. In case of bi-directional
+		 * time sync, TMU handshake is initiated by downstream router.
+		 * Therefore, we change the rate to off in the respective
+		 * router.
+		 */
+		if (unidirectional)
+			tb_switch_tmu_rate_write(parent, TB_SWITCH_TMU_RATE_OFF);
+		else
+			tb_switch_tmu_rate_write(sw, TB_SWITCH_TMU_RATE_OFF);
 
-		/* The switch may be unplugged so ignore any errors */
-		tb_port_tmu_unidirectional_disable(up);
-		ret = tb_port_tmu_unidirectional_disable(down);
+		tb_port_tmu_time_sync_disable(up);
+		ret = tb_port_tmu_time_sync_disable(down);
 		if (ret)
 			return ret;
-	}
 
-	tb_switch_tmu_rate_write(sw, TB_SWITCH_TMU_RATE_OFF);
+		if (unidirectional) {
+			/* The switch may be unplugged so ignore any errors */
+			tb_port_tmu_unidirectional_disable(up);
+			ret = tb_port_tmu_unidirectional_disable(down);
+			if (ret)
+				return ret;
+		}
+	} else {
+		tb_switch_tmu_rate_write(sw, TB_SWITCH_TMU_RATE_OFF);
+	}
 
 	sw->tmu.unidirectional = false;
 	sw->tmu.rate = TB_SWITCH_TMU_RATE_OFF;
···
 	return 0;
 }
 
-/**
- * tb_switch_tmu_enable() - Enable TMU on a switch
- * @sw: Switch whose TMU to enable
- *
- * Enables TMU of a switch to be in bi-directional, HiFi mode. In this mode
- * all tunneling should work.
- */
-int tb_switch_tmu_enable(struct tb_switch *sw)
+static void __tb_switch_tmu_off(struct tb_switch *sw, bool unidirectional)
 {
+	struct tb_switch *parent = tb_switch_parent(sw);
+	struct tb_port *down, *up;
+
+	down = tb_port_at(tb_route(sw), parent);
+	up = tb_upstream_port(sw);
+	/*
+	 * In case of any failure in one of the steps when setting
+	 * bi-directional or uni-directional TMU mode, get back to the TMU
+	 * configurations in off mode. In case of additional failures in
+	 * the functions below, ignore them since the caller shall already
+	 * report a failure.
+	 */
+	tb_port_tmu_time_sync_disable(down);
+	tb_port_tmu_time_sync_disable(up);
+	if (unidirectional)
+		tb_switch_tmu_rate_write(parent, TB_SWITCH_TMU_RATE_OFF);
+	else
+		tb_switch_tmu_rate_write(sw, TB_SWITCH_TMU_RATE_OFF);
+
+	tb_port_tmu_unidirectional_disable(down);
+	tb_port_tmu_unidirectional_disable(up);
+}
+
+/*
+ * This function is called when the previous TMU mode was
+ * TB_SWITCH_TMU_RATE_OFF.
+ */
+static int __tb_switch_tmu_enable_bidirectional(struct tb_switch *sw)
+{
+	struct tb_switch *parent = tb_switch_parent(sw);
+	struct tb_port *up, *down;
 	int ret;
+
+	up = tb_upstream_port(sw);
+	down = tb_port_at(tb_route(sw), parent);
+
+	ret = tb_port_tmu_unidirectional_disable(up);
+	if (ret)
+		return ret;
+
+	ret = tb_port_tmu_unidirectional_disable(down);
+	if (ret)
+		goto out;
+
+	ret = tb_switch_tmu_rate_write(sw, TB_SWITCH_TMU_RATE_HIFI);
+	if (ret)
+		goto out;
+
+	ret = tb_port_tmu_time_sync_enable(up);
+	if (ret)
+		goto out;
+
+	ret = tb_port_tmu_time_sync_enable(down);
+	if (ret)
+		goto out;
+
+	return 0;
+
+out:
+	__tb_switch_tmu_off(sw, false);
+	return ret;
+}
+
+/*
+ * This function is called when the previous TMU mode was
+ * TB_SWITCH_TMU_RATE_OFF.
+ */
+static int __tb_switch_tmu_enable_unidirectional(struct tb_switch *sw)
+{
+	struct tb_switch *parent = tb_switch_parent(sw);
+	struct tb_port *up, *down;
+	int ret;
+
+	up = tb_upstream_port(sw);
+	down = tb_port_at(tb_route(sw), parent);
+	ret = tb_switch_tmu_rate_write(parent, TB_SWITCH_TMU_RATE_HIFI);
+	if (ret)
+		return ret;
+
+	ret = tb_port_tmu_unidirectional_enable(up);
+	if (ret)
+		goto out;
+
+	ret = tb_port_tmu_time_sync_enable(up);
+	if (ret)
+		goto out;
+
+	ret = tb_port_tmu_unidirectional_enable(down);
+	if (ret)
+		goto out;
+
+	ret = tb_port_tmu_time_sync_enable(down);
+	if (ret)
+		goto out;
+
+	return 0;
+
+out:
+	__tb_switch_tmu_off(sw, true);
+	return ret;
+}
+
+static int tb_switch_tmu_hifi_enable(struct tb_switch *sw)
+{
+	bool unidirectional = sw->tmu.unidirectional_request;
+	int ret;
+
+	if (unidirectional && !sw->tmu.has_ucap)
+		return -EOPNOTSUPP;
 
 	if (!tb_switch_is_usb4(sw))
 		return 0;
 
-	if (tb_switch_tmu_is_enabled(sw))
+	if (tb_switch_tmu_hifi_is_enabled(sw, sw->tmu.unidirectional_request))
 		return 0;
 
 	ret = tb_switch_tmu_set_time_disruption(sw, true);
 	if (ret)
 		return ret;
 
-	/* Change mode to bi-directional */
-	if (tb_route(sw) && sw->tmu.unidirectional) {
-		struct tb_switch *parent = tb_switch_parent(sw);
-		struct tb_port *up, *down;
-
-		up = tb_upstream_port(sw);
-		down = tb_port_at(tb_route(sw), parent);
-
-		ret = tb_port_tmu_unidirectional_disable(down);
-		if (ret)
-			return ret;
-
-		ret = tb_switch_tmu_rate_write(sw, TB_SWITCH_TMU_RATE_HIFI);
-		if (ret)
-			return ret;
-
-		ret = tb_port_tmu_unidirectional_disable(up);
-		if (ret)
-			return ret;
+	if (tb_route(sw)) {
+		/* The used mode changes are from OFF to HiFi-Uni/HiFi-BiDir */
+		if (sw->tmu.rate == TB_SWITCH_TMU_RATE_OFF) {
+			if (unidirectional)
+				ret = __tb_switch_tmu_enable_unidirectional(sw);
+			else
+				ret = __tb_switch_tmu_enable_bidirectional(sw);
+			if (ret)
+				return ret;
+		}
+		sw->tmu.unidirectional = unidirectional;
 	} else {
+		/*
+		 * Host router port configurations are written as
+		 * part of configurations for downstream port of the parent
+		 * of the child node - see above.
+		 * Here only the host router' rate configuration is written.
+		 */
 		ret = tb_switch_tmu_rate_write(sw, TB_SWITCH_TMU_RATE_HIFI);
 		if (ret)
 			return ret;
 	}
 
-	sw->tmu.unidirectional = false;
 	sw->tmu.rate = TB_SWITCH_TMU_RATE_HIFI;
-	tb_sw_dbg(sw, "TMU: mode set to: %s\n", tb_switch_tmu_mode_name(sw));
 
+	tb_sw_dbg(sw, "TMU: mode set to: %s\n", tb_switch_tmu_mode_name(sw));
 	return tb_switch_tmu_set_time_disruption(sw, false);
+}
+
+/**
+ * tb_switch_tmu_enable() - Enable TMU on a router
+ * @sw: Router whose TMU to enable
+ *
+ * Enables TMU of a router to be in uni-directional or bi-directional HiFi mode.
+ * Calling tb_switch_tmu_configure() is required before calling this function,
+ * to select the mode HiFi and directionality (uni-directional/bi-directional).
+ * In both modes all tunneling should work. Uni-directional mode is required for
+ * CLx (Link Low-Power) to work.
+ */
+int tb_switch_tmu_enable(struct tb_switch *sw)
+{
+	if (sw->tmu.rate_request == TB_SWITCH_TMU_RATE_NORMAL)
+		return -EOPNOTSUPP;
+
+	return tb_switch_tmu_hifi_enable(sw);
+}
+
+/**
+ * tb_switch_tmu_configure() - Configure the TMU rate and directionality
+ * @sw: Router whose mode to change
+ * @rate: Rate to configure Off/LowRes/HiFi
+ * @unidirectional: If uni-directional (bi-directional otherwise)
+ *
+ * Selects the rate of the TMU and directionality (uni-directional or
+ * bi-directional). Must be called before tb_switch_tmu_enable().
+ */
+void tb_switch_tmu_configure(struct tb_switch *sw,
+			     enum tb_switch_tmu_rate rate, bool unidirectional)
+{
+	sw->tmu.unidirectional_request = unidirectional;
+	sw->tmu.rate_request = rate;
 }