thunderbolt: Add support for receiver lane margining

USB4 spec defines standard set of registers to be used for receiver lane
margining. This is useful for I/O interface quality and electrical
robustness validation during manufacturing. Expose receiver lane
margining through new debugfs directory "margining" that is added under
each connected USB4 port. Users can then run the margining by writing to
the exposed attributes under that directory.

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

1 files changed, 836 insertions, 0 deletions

diff --git a/drivers/thunderbolt/debugfs.c b/drivers/thunderbolt/debugfs.c
index c850b0ac098c..a1df3a7f159b 100644
--- a/drivers/thunderbolt/debugfs.c
+++ b/drivers/thunderbolt/debugfs.c
@@ -12,6 +12,7 @@
 #include <linux/uaccess.h>
 
 #include "tb.h"
+#include "sb_regs.h"
 
 #define PORT_CAP_PCIE_LEN	1
 #define PORT_CAP_POWER_LEN	2
@@ -187,6 +188,828 @@ static ssize_t switch_regs_write(struct file *file, const char __user *user_buf,
 #define DEBUGFS_MODE		0400
 #endif
 
+#if IS_ENABLED(CONFIG_USB4_DEBUGFS_MARGINING)
+/**
+ * struct tb_margining - Lane margining support
+ * @caps: Port lane margining capabilities
+ * @results: Last lane margining results
+ * @lanes: %0, %1 or %7 (all)
+ * @min_ber_level: Minimum supported BER level contour value
+ * @max_ber_level: Maximum supported BER level contour value
+ * @ber_level: Current BER level contour value
+ * @voltage_steps: Number of mandatory voltage steps
+ * @max_voltage_offset: Maximum mandatory voltage offset (in mV)
+ * @time_steps: Number of time margin steps
+ * @max_time_offset: Maximum time margin offset (in mUI)
+ * @software: %true if software margining is used instead of hardware
+ * @time: %true if time margining is used instead of voltage
+ * @right_high: %false if left/low margin test is performed, %true if
+ *		right/high
+ */
+struct tb_margining {
+	u32 caps[2];
+	u32 results[2];
+	unsigned int lanes;
+	unsigned int min_ber_level;
+	unsigned int max_ber_level;
+	unsigned int ber_level;
+	unsigned int voltage_steps;
+	unsigned int max_voltage_offset;
+	unsigned int time_steps;
+	unsigned int max_time_offset;
+	bool software;
+	bool time;
+	bool right_high;
+};
+
+static bool supports_software(const struct usb4_port *usb4)
+{
+	return usb4->margining->caps[0] & USB4_MARGIN_CAP_0_MODES_SW;
+}
+
+static bool supports_hardware(const struct usb4_port *usb4)
+{
+	return usb4->margining->caps[0] & USB4_MARGIN_CAP_0_MODES_HW;
+}
+
+static bool both_lanes(const struct usb4_port *usb4)
+{
+	return usb4->margining->caps[0] & USB4_MARGIN_CAP_0_2_LANES;
+}
+
+static unsigned int independent_voltage_margins(const struct usb4_port *usb4)
+{
+	return (usb4->margining->caps[0] & USB4_MARGIN_CAP_0_VOLTAGE_INDP_MASK) >>
+		USB4_MARGIN_CAP_0_VOLTAGE_INDP_SHIFT;
+}
+
+static bool supports_time(const struct usb4_port *usb4)
+{
+	return usb4->margining->caps[0] & USB4_MARGIN_CAP_0_TIME;
+}
+
+/* Only applicable if supports_time() returns true */
+static unsigned int independent_time_margins(const struct usb4_port *usb4)
+{
+	return (usb4->margining->caps[1] & USB4_MARGIN_CAP_1_TIME_INDP_MASK) >>
+		USB4_MARGIN_CAP_1_TIME_INDP_SHIFT;
+}
+
+static ssize_t
+margining_ber_level_write(struct file *file, const char __user *user_buf,
+			   size_t count, loff_t *ppos)
+{
+	struct seq_file *s = file->private_data;
+	struct tb_port *port = s->private;
+	struct usb4_port *usb4 = port->usb4;
+	struct tb *tb = port->sw->tb;
+	unsigned int val;
+	int ret = 0;
+	char *buf;
+
+	if (mutex_lock_interruptible(&tb->lock))
+		return -ERESTARTSYS;
+
+	if (usb4->margining->software) {
+		ret = -EINVAL;
+		goto out_unlock;
+	}
+
+	buf = validate_and_copy_from_user(user_buf, &count);
+	if (IS_ERR(buf)) {
+		ret = PTR_ERR(buf);
+		goto out_unlock;
+	}
+
+	buf[count - 1] = '\0';
+
+	ret = kstrtouint(buf, 10, &val);
+	if (ret)
+		goto out_free;
+
+	if (val < usb4->margining->min_ber_level ||
+	    val > usb4->margining->max_ber_level) {
+		ret = -EINVAL;
+		goto out_free;
+	}
+
+	usb4->margining->ber_level = val;
+
+out_free:
+	free_page((unsigned long)buf);
+out_unlock:
+	mutex_unlock(&tb->lock);
+
+	return ret < 0 ? ret : count;
+}
+
+static void ber_level_show(struct seq_file *s, unsigned int val)
+{
+	if (val % 2)
+		seq_printf(s, "3 * 1e%d (%u)\n", -12 + (val + 1) / 2, val);
+	else
+		seq_printf(s, "1e%d (%u)\n", -12 + val / 2, val);
+}
+
+static int margining_ber_level_show(struct seq_file *s, void *not_used)
+{
+	struct tb_port *port = s->private;
+	struct usb4_port *usb4 = port->usb4;
+
+	if (usb4->margining->software)
+		return -EINVAL;
+	ber_level_show(s, usb4->margining->ber_level);
+	return 0;
+}
+DEBUGFS_ATTR_RW(margining_ber_level);
+
+static int margining_caps_show(struct seq_file *s, void *not_used)
+{
+	struct tb_port *port = s->private;
+	struct usb4_port *usb4 = port->usb4;
+	struct tb *tb = port->sw->tb;
+	u32 cap0, cap1;
+
+	if (mutex_lock_interruptible(&tb->lock))
+		return -ERESTARTSYS;
+
+	/* Dump the raw caps first */
+	cap0 = usb4->margining->caps[0];
+	seq_printf(s, "0x%08x\n", cap0);
+	cap1 = usb4->margining->caps[1];
+	seq_printf(s, "0x%08x\n", cap1);
+
+	seq_printf(s, "# software margining: %s\n",
+		   supports_software(usb4) ? "yes" : "no");
+	if (supports_hardware(usb4)) {
+		seq_puts(s, "# hardware margining: yes\n");
+		seq_puts(s, "# minimum BER level contour: ");
+		ber_level_show(s, usb4->margining->min_ber_level);
+		seq_puts(s, "# maximum BER level contour: ");
+		ber_level_show(s, usb4->margining->max_ber_level);
+	} else {
+		seq_puts(s, "# hardware margining: no\n");
+	}
+
+	seq_printf(s, "# both lanes simultaneusly: %s\n",
+		  both_lanes(usb4) ? "yes" : "no");
+	seq_printf(s, "# voltage margin steps: %u\n",
+		   usb4->margining->voltage_steps);
+	seq_printf(s, "# maximum voltage offset: %u mV\n",
+		   usb4->margining->max_voltage_offset);
+
+	switch (independent_voltage_margins(usb4)) {
+	case USB4_MARGIN_CAP_0_VOLTAGE_MIN:
+		seq_puts(s, "# returns minimum between high and low voltage margins\n");
+		break;
+	case USB4_MARGIN_CAP_0_VOLTAGE_HL:
+		seq_puts(s, "# returns high or low voltage margin\n");
+		break;
+	case USB4_MARGIN_CAP_0_VOLTAGE_BOTH:
+		seq_puts(s, "# returns both hight and low margings\n");
+		break;
+	}
+
+	if (supports_time(usb4)) {
+		seq_puts(s, "# time margining: yes\n");
+		seq_printf(s, "# time margining is destructive: %s\n",
+			   cap1 & USB4_MARGIN_CAP_1_TIME_DESTR ? "yes" : "no");
+
+		switch (independent_time_margins(usb4)) {
+		case USB4_MARGIN_CAP_1_TIME_MIN:
+			seq_puts(s, "# returns minimum between left and right time margins\n");
+			break;
+		case USB4_MARGIN_CAP_1_TIME_LR:
+			seq_puts(s, "# returns left or right margin\n");
+			break;
+		case USB4_MARGIN_CAP_1_TIME_BOTH:
+			seq_puts(s, "# returns both left and right margins\n");
+			break;
+		}
+
+		seq_printf(s, "# time margin steps: %u\n",
+			   usb4->margining->time_steps);
+		seq_printf(s, "# maximum time offset: %u mUI\n",
+			   usb4->margining->max_time_offset);
+	} else {
+		seq_puts(s, "# time margining: no\n");
+	}
+
+	mutex_unlock(&tb->lock);
+	return 0;
+}
+DEBUGFS_ATTR_RO(margining_caps);
+
+static ssize_t
+margining_lanes_write(struct file *file, const char __user *user_buf,
+		      size_t count, loff_t *ppos)
+{
+	struct seq_file *s = file->private_data;
+	struct tb_port *port = s->private;
+	struct usb4_port *usb4 = port->usb4;
+	struct tb *tb = port->sw->tb;
+	int ret = 0;
+	char *buf;
+
+	buf = validate_and_copy_from_user(user_buf, &count);
+	if (IS_ERR(buf))
+		return PTR_ERR(buf);
+
+	buf[count - 1] = '\0';
+
+	if (mutex_lock_interruptible(&tb->lock)) {
+		ret = -ERESTARTSYS;
+		goto out_free;
+	}
+
+	if (!strcmp(buf, "0")) {
+		usb4->margining->lanes = 0;
+	} else if (!strcmp(buf, "1")) {
+		usb4->margining->lanes = 1;
+	} else if (!strcmp(buf, "all")) {
+		/* Needs to be supported */
+		if (both_lanes(usb4))
+			usb4->margining->lanes = 7;
+		else
+			ret = -EINVAL;
+	} else {
+		ret = -EINVAL;
+	}
+
+	mutex_unlock(&tb->lock);
+
+out_free:
+	free_page((unsigned long)buf);
+	return ret < 0 ? ret : count;
+}
+
+static int margining_lanes_show(struct seq_file *s, void *not_used)
+{
+	struct tb_port *port = s->private;
+	struct usb4_port *usb4 = port->usb4;
+	struct tb *tb = port->sw->tb;
+	unsigned int lanes;
+
+	if (mutex_lock_interruptible(&tb->lock))
+		return -ERESTARTSYS;
+
+	lanes = usb4->margining->lanes;
+	if (both_lanes(usb4)) {
+		if (!lanes)
+			seq_puts(s, "[0] 1 all\n");
+		else if (lanes == 1)
+			seq_puts(s, "0 [1] all\n");
+		else
+			seq_puts(s, "0 1 [all]\n");
+	} else {
+		if (!lanes)
+			seq_puts(s, "[0] 1\n");
+		else
+			seq_puts(s, "0 [1]\n");
+	}
+
+	mutex_unlock(&tb->lock);
+	return 0;
+}
+DEBUGFS_ATTR_RW(margining_lanes);
+
+static ssize_t margining_mode_write(struct file *file,
+				   const char __user *user_buf,
+				   size_t count, loff_t *ppos)
+{
+	struct seq_file *s = file->private_data;
+	struct tb_port *port = s->private;
+	struct usb4_port *usb4 = port->usb4;
+	struct tb *tb = port->sw->tb;
+	int ret = 0;
+	char *buf;
+
+	buf = validate_and_copy_from_user(user_buf, &count);
+	if (IS_ERR(buf))
+		return PTR_ERR(buf);
+
+	buf[count - 1] = '\0';
+
+	if (mutex_lock_interruptible(&tb->lock)) {
+		ret = -ERESTARTSYS;
+		goto out_free;
+	}
+
+	if (!strcmp(buf, "software")) {
+		if (supports_software(usb4))
+			usb4->margining->software = true;
+		else
+			ret = -EINVAL;
+	} else if (!strcmp(buf, "hardware")) {
+		if (supports_hardware(usb4))
+			usb4->margining->software = false;
+		else
+			ret = -EINVAL;
+	} else {
+		ret = -EINVAL;
+	}
+
+	mutex_unlock(&tb->lock);
+
+out_free:
+	free_page((unsigned long)buf);
+	return ret ? ret : count;
+}
+
+static int margining_mode_show(struct seq_file *s, void *not_used)
+{
+	const struct tb_port *port = s->private;
+	const struct usb4_port *usb4 = port->usb4;
+	struct tb *tb = port->sw->tb;
+	const char *space = "";
+
+	if (mutex_lock_interruptible(&tb->lock))
+		return -ERESTARTSYS;
+
+	if (supports_software(usb4)) {
+		if (usb4->margining->software)
+			seq_puts(s, "[software]");
+		else
+			seq_puts(s, "software");
+		space = " ";
+	}
+	if (supports_hardware(usb4)) {
+		if (usb4->margining->software)
+			seq_printf(s, "%shardware", space);
+		else
+			seq_printf(s, "%s[hardware]", space);
+	}
+
+	mutex_unlock(&tb->lock);
+
+	seq_puts(s, "\n");
+	return 0;
+}
+DEBUGFS_ATTR_RW(margining_mode);
+
+static int margining_run_write(void *data, u64 val)
+{
+	struct tb_port *port = data;
+	struct usb4_port *usb4 = port->usb4;
+	struct tb_switch *sw = port->sw;
+	struct tb_margining *margining;
+	struct tb *tb = sw->tb;
+	int ret;
+
+	if (val != 1)
+		return -EINVAL;
+
+	pm_runtime_get_sync(&sw->dev);
+
+	if (mutex_lock_interruptible(&tb->lock)) {
+		ret = -ERESTARTSYS;
+		goto out_rpm_put;
+	}
+
+	/*
+	 * CL states may interfere with lane margining so inform the user know
+	 * and bail out.
+	 */
+	if (tb_port_is_clx_enabled(port, TB_CL1 | TB_CL2)) {
+		tb_port_warn(port,
+			     "CL states are enabled, Disable them with clx=0 and re-connect\n");
+		ret = -EINVAL;
+		goto out_unlock;
+	}
+
+	margining = usb4->margining;
+
+	if (margining->software) {
+		tb_port_dbg(port, "running software %s lane margining for lanes %u\n",
+			    margining->time ? "time" : "voltage", margining->lanes);
+		ret = usb4_port_sw_margin(port, margining->lanes, margining->time,
+					  margining->right_high,
+					  USB4_MARGIN_SW_COUNTER_CLEAR);
+		if (ret)
+			goto out_unlock;
+
+		ret = usb4_port_sw_margin_errors(port, &margining->results[0]);
+	} else {
+		tb_port_dbg(port, "running hardware %s lane margining for lanes %u\n",
+			    margining->time ? "time" : "voltage", margining->lanes);
+		/* Clear the results */
+		margining->results[0] = 0;
+		margining->results[1] = 0;
+		ret = usb4_port_hw_margin(port, margining->lanes,
+					  margining->ber_level, margining->time,
+					  margining->right_high, margining->results);
+	}
+
+out_unlock:
+	mutex_unlock(&tb->lock);
+out_rpm_put:
+	pm_runtime_mark_last_busy(&sw->dev);
+	pm_runtime_put_autosuspend(&sw->dev);
+
+	return ret;
+}
+DEFINE_DEBUGFS_ATTRIBUTE(margining_run_fops, NULL, margining_run_write,
+			 "%llu\n");
+
+static ssize_t margining_results_write(struct file *file,
+				       const char __user *user_buf,
+				       size_t count, loff_t *ppos)
+{
+	struct seq_file *s = file->private_data;
+	struct tb_port *port = s->private;
+	struct usb4_port *usb4 = port->usb4;
+	struct tb *tb = port->sw->tb;
+
+	if (mutex_lock_interruptible(&tb->lock))
+		return -ERESTARTSYS;
+
+	/* Just clear the results */
+	usb4->margining->results[0] = 0;
+	usb4->margining->results[1] = 0;
+
+	mutex_unlock(&tb->lock);
+	return count;
+}
+
+static void voltage_margin_show(struct seq_file *s,
+				const struct tb_margining *margining, u8 val)
+{
+	unsigned int tmp, voltage;
+
+	tmp = val & USB4_MARGIN_HW_RES_1_MARGIN_MASK;
+	voltage = tmp * margining->max_voltage_offset / margining->voltage_steps;
+	seq_printf(s, "%u mV (%u)", voltage, tmp);
+	if (val & USB4_MARGIN_HW_RES_1_EXCEEDS)
+		seq_puts(s, " exceeds maximum");
+	seq_puts(s, "\n");
+}
+
+static void time_margin_show(struct seq_file *s,
+			     const struct tb_margining *margining, u8 val)
+{
+	unsigned int tmp, interval;
+
+	tmp = val & USB4_MARGIN_HW_RES_1_MARGIN_MASK;
+	interval = tmp * margining->max_time_offset / margining->time_steps;
+	seq_printf(s, "%u mUI (%u)", interval, tmp);
+	if (val & USB4_MARGIN_HW_RES_1_EXCEEDS)
+		seq_puts(s, " exceeds maximum");
+	seq_puts(s, "\n");
+}
+
+static int margining_results_show(struct seq_file *s, void *not_used)
+{
+	struct tb_port *port = s->private;
+	struct usb4_port *usb4 = port->usb4;
+	struct tb_margining *margining;
+	struct tb *tb = port->sw->tb;
+
+	if (mutex_lock_interruptible(&tb->lock))
+		return -ERESTARTSYS;
+
+	margining = usb4->margining;
+	/* Dump the raw results first */
+	seq_printf(s, "0x%08x\n", margining->results[0]);
+	/* Only the hardware margining has two result dwords */
+	if (!margining->software) {
+		unsigned int val;
+
+		seq_printf(s, "0x%08x\n", margining->results[1]);
+
+		if (margining->time) {
+			if (!margining->lanes || margining->lanes == 7) {
+				val = margining->results[1];
+				seq_puts(s, "# lane 0 right time margin: ");
+				time_margin_show(s, margining, val);
+				val = margining->results[1] >>
+					USB4_MARGIN_HW_RES_1_L0_LL_MARGIN_SHIFT;
+				seq_puts(s, "# lane 0 left time margin: ");
+				time_margin_show(s, margining, val);
+			}
+			if (margining->lanes == 1 || margining->lanes == 7) {
+				val = margining->results[1] >>
+					USB4_MARGIN_HW_RES_1_L1_RH_MARGIN_SHIFT;
+				seq_puts(s, "# lane 1 right time margin: ");
+				time_margin_show(s, margining, val);
+				val = margining->results[1] >>
+					USB4_MARGIN_HW_RES_1_L1_LL_MARGIN_SHIFT;
+				seq_puts(s, "# lane 1 left time margin: ");
+				time_margin_show(s, margining, val);
+			}
+		} else {
+			if (!margining->lanes || margining->lanes == 7) {
+				val = margining->results[1];
+				seq_puts(s, "# lane 0 high voltage margin: ");
+				voltage_margin_show(s, margining, val);
+				val = margining->results[1] >>
+					USB4_MARGIN_HW_RES_1_L0_LL_MARGIN_SHIFT;
+				seq_puts(s, "# lane 0 low voltage margin: ");
+				voltage_margin_show(s, margining, val);
+			}
+			if (margining->lanes == 1 || margining->lanes == 7) {
+				val = margining->results[1] >>
+					USB4_MARGIN_HW_RES_1_L1_RH_MARGIN_SHIFT;
+				seq_puts(s, "# lane 1 high voltage margin: ");
+				voltage_margin_show(s, margining, val);
+				val = margining->results[1] >>
+					USB4_MARGIN_HW_RES_1_L1_LL_MARGIN_SHIFT;
+				seq_puts(s, "# lane 1 low voltage margin: ");
+				voltage_margin_show(s, margining, val);
+			}
+		}
+	}
+
+	mutex_unlock(&tb->lock);
+	return 0;
+}
+DEBUGFS_ATTR_RW(margining_results);
+
+static ssize_t margining_test_write(struct file *file,
+				    const char __user *user_buf,
+				    size_t count, loff_t *ppos)
+{
+	struct seq_file *s = file->private_data;
+	struct tb_port *port = s->private;
+	struct usb4_port *usb4 = port->usb4;
+	struct tb *tb = port->sw->tb;
+	int ret = 0;
+	char *buf;
+
+	buf = validate_and_copy_from_user(user_buf, &count);
+	if (IS_ERR(buf))
+		return PTR_ERR(buf);
+
+	buf[count - 1] = '\0';
+
+	if (mutex_lock_interruptible(&tb->lock)) {
+		ret = -ERESTARTSYS;
+		goto out_free;
+	}
+
+	if (!strcmp(buf, "time") && supports_time(usb4))
+		usb4->margining->time = true;
+	else if (!strcmp(buf, "voltage"))
+		usb4->margining->time = false;
+	else
+		ret = -EINVAL;
+
+	mutex_unlock(&tb->lock);
+
+out_free:
+	free_page((unsigned long)buf);
+	return ret ? ret : count;
+}
+
+static int margining_test_show(struct seq_file *s, void *not_used)
+{
+	struct tb_port *port = s->private;
+	struct usb4_port *usb4 = port->usb4;
+	struct tb *tb = port->sw->tb;
+
+	if (mutex_lock_interruptible(&tb->lock))
+		return -ERESTARTSYS;
+
+	if (supports_time(usb4)) {
+		if (usb4->margining->time)
+			seq_puts(s, "voltage [time]\n");
+		else
+			seq_puts(s, "[voltage] time\n");
+	} else {
+		seq_puts(s, "[voltage]\n");
+	}
+
+	mutex_unlock(&tb->lock);
+	return 0;
+}
+DEBUGFS_ATTR_RW(margining_test);
+
+static ssize_t margining_margin_write(struct file *file,
+				    const char __user *user_buf,
+				    size_t count, loff_t *ppos)
+{
+	struct seq_file *s = file->private_data;
+	struct tb_port *port = s->private;
+	struct usb4_port *usb4 = port->usb4;
+	struct tb *tb = port->sw->tb;
+	int ret = 0;
+	char *buf;
+
+	buf = validate_and_copy_from_user(user_buf, &count);
+	if (IS_ERR(buf))
+		return PTR_ERR(buf);
+
+	buf[count - 1] = '\0';
+
+	if (mutex_lock_interruptible(&tb->lock)) {
+		ret = -ERESTARTSYS;
+		goto out_free;
+	}
+
+	if (usb4->margining->time) {
+		if (!strcmp(buf, "left"))
+			usb4->margining->right_high = false;
+		else if (!strcmp(buf, "right"))
+			usb4->margining->right_high = true;
+		else
+			ret = -EINVAL;
+	} else {
+		if (!strcmp(buf, "low"))
+			usb4->margining->right_high = false;
+		else if (!strcmp(buf, "high"))
+			usb4->margining->right_high = true;
+		else
+			ret = -EINVAL;
+	}
+
+	mutex_unlock(&tb->lock);
+
+out_free:
+	free_page((unsigned long)buf);
+	return ret ? ret : count;
+}
+
+static int margining_margin_show(struct seq_file *s, void *not_used)
+{
+	struct tb_port *port = s->private;
+	struct usb4_port *usb4 = port->usb4;
+	struct tb *tb = port->sw->tb;
+
+	if (mutex_lock_interruptible(&tb->lock))
+		return -ERESTARTSYS;
+
+	if (usb4->margining->time) {
+		if (usb4->margining->right_high)
+			seq_puts(s, "left [right]\n");
+		else
+			seq_puts(s, "[left] right\n");
+	} else {
+		if (usb4->margining->right_high)
+			seq_puts(s, "low [high]\n");
+		else
+			seq_puts(s, "[low] high\n");
+	}
+
+	mutex_unlock(&tb->lock);
+	return 0;
+}
+DEBUGFS_ATTR_RW(margining_margin);
+
+static void margining_port_init(struct tb_port *port)
+{
+	struct tb_margining *margining;
+	struct dentry *dir, *parent;
+	struct usb4_port *usb4;
+	char dir_name[10];
+	unsigned int val;
+	int ret;
+
+	usb4 = port->usb4;
+	if (!usb4)
+		return;
+
+	snprintf(dir_name, sizeof(dir_name), "port%d", port->port);
+	parent = debugfs_lookup(dir_name, port->sw->debugfs_dir);
+
+	margining = kzalloc(sizeof(*margining), GFP_KERNEL);
+	if (!margining)
+		return;
+
+	ret = usb4_port_margining_caps(port, margining->caps);
+	if (ret) {
+		kfree(margining);
+		return;
+	}
+
+	usb4->margining = margining;
+
+	/* Set the initial mode */
+	if (supports_software(usb4))
+		margining->software = true;
+
+	val = (margining->caps[0] & USB4_MARGIN_CAP_0_VOLTAGE_STEPS_MASK) >>
+		USB4_MARGIN_CAP_0_VOLTAGE_STEPS_SHIFT;
+	margining->voltage_steps = val;
+	val = (margining->caps[0] & USB4_MARGIN_CAP_0_MAX_VOLTAGE_OFFSET_MASK) >>
+		USB4_MARGIN_CAP_0_MAX_VOLTAGE_OFFSET_SHIFT;
+	margining->max_voltage_offset = 74 + val * 2;
+
+	if (supports_time(usb4)) {
+		val = (margining->caps[1] & USB4_MARGIN_CAP_1_TIME_STEPS_MASK) >>
+			USB4_MARGIN_CAP_1_TIME_STEPS_SHIFT;
+		margining->time_steps = val;
+		val = (margining->caps[1] & USB4_MARGIN_CAP_1_TIME_OFFSET_MASK) >>
+			USB4_MARGIN_CAP_1_TIME_OFFSET_SHIFT;
+		/*
+		 * Store it as mUI (milli Unit Interval) because we want
+		 * to keep it as integer.
+		 */
+		margining->max_time_offset = 200 + 10 * val;
+	}
+
+	dir = debugfs_create_dir("margining", parent);
+	if (supports_hardware(usb4)) {
+		val = (margining->caps[1] & USB4_MARGIN_CAP_1_MIN_BER_MASK) >>
+			USB4_MARGIN_CAP_1_MIN_BER_SHIFT;
+		margining->min_ber_level = val;
+		val = (margining->caps[1] & USB4_MARGIN_CAP_1_MAX_BER_MASK) >>
+			USB4_MARGIN_CAP_1_MAX_BER_SHIFT;
+		margining->max_ber_level = val;
+
+		/* Set the default to minimum */
+		margining->ber_level = margining->min_ber_level;
+
+		debugfs_create_file("ber_level_contour", 0400, dir, port,
+				    &margining_ber_level_fops);
+	}
+	debugfs_create_file("caps", 0400, dir, port, &margining_caps_fops);
+	debugfs_create_file("lanes", 0600, dir, port, &margining_lanes_fops);
+	debugfs_create_file("mode", 0600, dir, port, &margining_mode_fops);
+	debugfs_create_file("run", 0600, dir, port, &margining_run_fops);
+	debugfs_create_file("results", 0600, dir, port, &margining_results_fops);
+	debugfs_create_file("test", 0600, dir, port, &margining_test_fops);
+	if (independent_voltage_margins(usb4) ||
+	    (supports_time(usb4) && independent_time_margins(usb4)))
+		debugfs_create_file("margin", 0600, dir, port, &margining_margin_fops);
+}
+
+static void margining_port_remove(struct tb_port *port)
+{
+	struct dentry *parent;
+	char dir_name[10];
+
+	if (!port->usb4)
+		return;
+
+	snprintf(dir_name, sizeof(dir_name), "port%d", port->port);
+	parent = debugfs_lookup(dir_name, port->sw->debugfs_dir);
+	debugfs_remove_recursive(debugfs_lookup("margining", parent));
+
+	kfree(port->usb4->margining);
+	port->usb4->margining = NULL;
+}
+
+static void margining_switch_init(struct tb_switch *sw)
+{
+	struct tb_port *upstream, *downstream;
+	struct tb_switch *parent_sw;
+	u64 route = tb_route(sw);
+
+	if (!route)
+		return;
+
+	upstream = tb_upstream_port(sw);
+	parent_sw = tb_switch_parent(sw);
+	downstream = tb_port_at(route, parent_sw);
+
+	margining_port_init(downstream);
+	margining_port_init(upstream);
+}
+
+static void margining_switch_remove(struct tb_switch *sw)
+{
+	struct tb_switch *parent_sw;
+	struct tb_port *downstream;
+	u64 route = tb_route(sw);
+
+	if (!route)
+		return;
+
+	/*
+	 * Upstream is removed with the router itself but we need to
+	 * remove the downstream port margining directory.
+	 */
+	parent_sw = tb_switch_parent(sw);
+	downstream = tb_port_at(route, parent_sw);
+	margining_port_remove(downstream);
+}
+
+static void margining_xdomain_init(struct tb_xdomain *xd)
+{
+	struct tb_switch *parent_sw;
+	struct tb_port *downstream;
+
+	parent_sw = tb_xdomain_parent(xd);
+	downstream = tb_port_at(xd->route, parent_sw);
+
+	margining_port_init(downstream);
+}
+
+static void margining_xdomain_remove(struct tb_xdomain *xd)
+{
+	struct tb_switch *parent_sw;
+	struct tb_port *downstream;
+
+	parent_sw = tb_xdomain_parent(xd);
+	downstream = tb_port_at(xd->route, parent_sw);
+	margining_port_remove(downstream);
+}
+#else
+static inline void margining_switch_init(struct tb_switch *sw) { }
+static inline void margining_switch_remove(struct tb_switch *sw) { }
+static inline void margining_xdomain_init(struct tb_xdomain *xd) { }
+static inline void margining_xdomain_remove(struct tb_xdomain *xd) { }
+#endif
+
 static int port_clear_all_counters(struct tb_port *port)
 {
 	u32 *buf;
@@ -689,6 +1512,8 @@ void tb_switch_debugfs_init(struct tb_switch *sw)
 			debugfs_create_file("counters", 0600, debugfs_dir, port,
 					    &counters_fops);
 	}
+
+	margining_switch_init(sw);
 }
 
 /**
@@ -699,9 +1524,20 @@ void tb_switch_debugfs_init(struct tb_switch *sw)
  */
 void tb_switch_debugfs_remove(struct tb_switch *sw)
 {
+	margining_switch_remove(sw);
 	debugfs_remove_recursive(sw->debugfs_dir);
 }
 
+void tb_xdomain_debugfs_init(struct tb_xdomain *xd)
+{
+	margining_xdomain_init(xd);
+}
+
+void tb_xdomain_debugfs_remove(struct tb_xdomain *xd)
+{
+	margining_xdomain_remove(xd);
+}
+
 /**
  * tb_service_debugfs_init() - Add debugfs directory for service
  * @svc: Thunderbolt service pointer