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>

drivers/thunderbolt/Kconfig

@@ -27,6 +27,16 @@ config USB4_DEBUGFS_WRITE
 	  Only enable this if you know what you are doing! Never enable
 	  this for production systems or distro kernels.
 
+config USB4_DEBUGFS_MARGINING
+	bool "Expose receiver lane margining operations under USB4 ports (DANGEROUS)"
+	depends on DEBUG_FS
+	depends on USB4_DEBUGFS_WRITE
+	help
+	  Enables hardware and software based receiver lane margining support
+	  under each USB4 port. Used for electrical quality and robustness
+	  validation during manufacturing. Should not be enabled by distro
+	  kernels.
+
 config USB4_KUNIT_TEST
 	bool "KUnit tests" if !KUNIT_ALL_TESTS
 	depends on (USB4=m || KUNIT=y)

drivers/thunderbolt/sb_regs.h

@@ -26,10 +26,68 @@ enum usb4_sb_opcode {
 	USB4_SB_OPCODE_NVM_BLOCK_WRITE = 0x574b4c42,		/* "BLKW" */
 	USB4_SB_OPCODE_NVM_AUTH_WRITE = 0x48545541,		/* "AUTH" */
 	USB4_SB_OPCODE_NVM_READ = 0x52524641,			/* "AFRR" */
+	USB4_SB_OPCODE_READ_LANE_MARGINING_CAP = 0x50434452,	/* "RDCP" */
+	USB4_SB_OPCODE_RUN_HW_LANE_MARGINING = 0x474d4852,	/* "RHMG" */
+	USB4_SB_OPCODE_RUN_SW_LANE_MARGINING = 0x474d5352,	/* "RSMG" */
+	USB4_SB_OPCODE_READ_SW_MARGIN_ERR = 0x57534452,		/* "RDSW" */
 };
 
 #define USB4_SB_METADATA			0x09
 #define USB4_SB_METADATA_NVM_AUTH_WRITE_MASK	GENMASK(5, 0)
 #define USB4_SB_DATA				0x12
 
+/* USB4_SB_OPCODE_READ_LANE_MARGINING_CAP */
+#define USB4_MARGIN_CAP_0_MODES_HW		BIT(0)
+#define USB4_MARGIN_CAP_0_MODES_SW		BIT(1)
+#define USB4_MARGIN_CAP_0_2_LANES		BIT(2)
+#define USB4_MARGIN_CAP_0_VOLTAGE_INDP_MASK	GENMASK(4, 3)
+#define USB4_MARGIN_CAP_0_VOLTAGE_INDP_SHIFT	3
+#define USB4_MARGIN_CAP_0_VOLTAGE_MIN		0x0
+#define USB4_MARGIN_CAP_0_VOLTAGE_HL		0x1
+#define USB4_MARGIN_CAP_0_VOLTAGE_BOTH		0x2
+#define USB4_MARGIN_CAP_0_TIME			BIT(5)
+#define USB4_MARGIN_CAP_0_VOLTAGE_STEPS_MASK	GENMASK(12, 6)
+#define USB4_MARGIN_CAP_0_VOLTAGE_STEPS_SHIFT	6
+#define USB4_MARGIN_CAP_0_MAX_VOLTAGE_OFFSET_MASK GENMASK(18, 13)
+#define USB4_MARGIN_CAP_0_MAX_VOLTAGE_OFFSET_SHIFT 13
+#define USB4_MARGIN_CAP_1_TIME_DESTR		BIT(8)
+#define USB4_MARGIN_CAP_1_TIME_INDP_MASK	GENMASK(10, 9)
+#define USB4_MARGIN_CAP_1_TIME_INDP_SHIFT	9
+#define USB4_MARGIN_CAP_1_TIME_MIN		0x0
+#define USB4_MARGIN_CAP_1_TIME_LR		0x1
+#define USB4_MARGIN_CAP_1_TIME_BOTH		0x2
+#define USB4_MARGIN_CAP_1_TIME_STEPS_MASK	GENMASK(15, 11)
+#define USB4_MARGIN_CAP_1_TIME_STEPS_SHIFT	11
+#define USB4_MARGIN_CAP_1_TIME_OFFSET_MASK	GENMASK(20, 16)
+#define USB4_MARGIN_CAP_1_TIME_OFFSET_SHIFT	16
+#define USB4_MARGIN_CAP_1_MIN_BER_MASK		GENMASK(25, 21)
+#define USB4_MARGIN_CAP_1_MIN_BER_SHIFT		21
+#define USB4_MARGIN_CAP_1_MAX_BER_MASK		GENMASK(30, 26)
+#define USB4_MARGIN_CAP_1_MAX_BER_SHIFT		26
+#define USB4_MARGIN_CAP_1_MAX_BER_SHIFT		26
+
+/* USB4_SB_OPCODE_RUN_HW_LANE_MARGINING */
+#define USB4_MARGIN_HW_TIME			BIT(3)
+#define USB4_MARGIN_HW_RH			BIT(4)
+#define USB4_MARGIN_HW_BER_MASK			GENMASK(9, 5)
+#define USB4_MARGIN_HW_BER_SHIFT		5
+
+/* Applicable to all margin values */
+#define USB4_MARGIN_HW_RES_1_MARGIN_MASK	GENMASK(6, 0)
+#define USB4_MARGIN_HW_RES_1_EXCEEDS		BIT(7)
+/* Different lane margin shifts */
+#define USB4_MARGIN_HW_RES_1_L0_LL_MARGIN_SHIFT	8
+#define USB4_MARGIN_HW_RES_1_L1_RH_MARGIN_SHIFT	16
+#define USB4_MARGIN_HW_RES_1_L1_LL_MARGIN_SHIFT	24
+
+/* USB4_SB_OPCODE_RUN_SW_LANE_MARGINING */
+#define USB4_MARGIN_SW_TIME			BIT(3)
+#define USB4_MARGIN_SW_RH			BIT(4)
+#define USB4_MARGIN_SW_COUNTER_MASK		GENMASK(14, 13)
+#define USB4_MARGIN_SW_COUNTER_SHIFT		13
+#define USB4_MARGIN_SW_COUNTER_NOP		0x0
+#define USB4_MARGIN_SW_COUNTER_CLEAR		0x1
+#define USB4_MARGIN_SW_COUNTER_START		0x2
+#define USB4_MARGIN_SW_COUNTER_STOP		0x3
+
 #endif

drivers/thunderbolt/tb.h

@@ -279,12 +279,16 @@ struct tb_port {
  * @can_offline: Does the port have necessary platform support to moved
  *		 it into offline mode and back
  * @offline: The port is currently in offline mode
+ * @margining: Pointer to margining structure if enabled
  */
 struct usb4_port {
 	struct device dev;
 	struct tb_port *port;
 	bool can_offline;
 	bool offline;
+#ifdef CONFIG_USB4_DEBUGFS_MARGINING
+	struct tb_margining *margining;
+#endif
 };
 
 /**
@@ -1188,6 +1192,13 @@ int usb4_port_router_offline(struct tb_port *port);
 int usb4_port_router_online(struct tb_port *port);
 int usb4_port_enumerate_retimers(struct tb_port *port);
 bool usb4_port_clx_supported(struct tb_port *port);
+int usb4_port_margining_caps(struct tb_port *port, u32 *caps);
+int usb4_port_hw_margin(struct tb_port *port, unsigned int lanes,
+			unsigned int ber_level, bool timing, bool right_high,
+			u32 *results);
+int usb4_port_sw_margin(struct tb_port *port, unsigned int lanes, bool timing,
+			bool right_high, u32 counter);
+int usb4_port_sw_margin_errors(struct tb_port *port, u32 *errors);
 
 int usb4_port_retimer_set_inbound_sbtx(struct tb_port *port, u8 index);
 int usb4_port_retimer_read(struct tb_port *port, u8 index, u8 reg, void *buf,
@@ -1270,6 +1281,8 @@ void tb_debugfs_init(void);
 void tb_debugfs_exit(void);
 void tb_switch_debugfs_init(struct tb_switch *sw);
 void tb_switch_debugfs_remove(struct tb_switch *sw);
+void tb_xdomain_debugfs_init(struct tb_xdomain *xd);
+void tb_xdomain_debugfs_remove(struct tb_xdomain *xd);
 void tb_service_debugfs_init(struct tb_service *svc);
 void tb_service_debugfs_remove(struct tb_service *svc);
 #else
@@ -1277,6 +1290,8 @@ static inline void tb_debugfs_init(void) { }
 static inline void tb_debugfs_exit(void) { }
 static inline void tb_switch_debugfs_init(struct tb_switch *sw) { }
 static inline void tb_switch_debugfs_remove(struct tb_switch *sw) { }
+static inline void tb_xdomain_debugfs_init(struct tb_xdomain *xd) { }
+static inline void tb_xdomain_debugfs_remove(struct tb_xdomain *xd) { }
 static inline void tb_service_debugfs_init(struct tb_service *svc) { }
 static inline void tb_service_debugfs_remove(struct tb_service *svc) { }
 #endif

drivers/thunderbolt/usb4.c

@@ -1384,6 +1384,126 @@ bool usb4_port_clx_supported(struct tb_port *port)
 	return !!(val & PORT_CS_18_CPS);
 }
 
+/**
+ * usb4_port_margining_caps() - Read USB4 port marginig capabilities
+ * @port: USB4 port
+ * @caps: Array with at least two elements to hold the results
+ *
+ * Reads the USB4 port lane margining capabilities into @caps.
+ */
+int usb4_port_margining_caps(struct tb_port *port, u32 *caps)
+{
+	int ret;
+
+	ret = usb4_port_sb_op(port, USB4_SB_TARGET_ROUTER, 0,
+			      USB4_SB_OPCODE_READ_LANE_MARGINING_CAP, 500);
+	if (ret)
+		return ret;
+
+	return usb4_port_sb_read(port, USB4_SB_TARGET_ROUTER, 0,
+				 USB4_SB_DATA, caps, sizeof(*caps) * 2);
+}
+
+/**
+ * usb4_port_hw_margin() - Run hardware lane margining on port
+ * @port: USB4 port
+ * @lanes: Which lanes to run (must match the port capabilities). Can be
+ *	   %0, %1 or %7.
+ * @ber_level: BER level contour value
+ * @timing: Perform timing margining instead of voltage
+ * @right_high: Use Right/high margin instead of left/low
+ * @results: Array with at least two elements to hold the results
+ *
+ * Runs hardware lane margining on USB4 port and returns the result in
+ * @results.
+ */
+int usb4_port_hw_margin(struct tb_port *port, unsigned int lanes,
+			unsigned int ber_level, bool timing, bool right_high,
+			u32 *results)
+{
+	u32 val;
+	int ret;
+
+	val = lanes;
+	if (timing)
+		val |= USB4_MARGIN_HW_TIME;
+	if (right_high)
+		val |= USB4_MARGIN_HW_RH;
+	if (ber_level)
+		val |= (ber_level << USB4_MARGIN_HW_BER_SHIFT) &
+			USB4_MARGIN_HW_BER_MASK;
+
+	ret = usb4_port_sb_write(port, USB4_SB_TARGET_ROUTER, 0,
+				 USB4_SB_METADATA, &val, sizeof(val));
+	if (ret)
+		return ret;
+
+	ret = usb4_port_sb_op(port, USB4_SB_TARGET_ROUTER, 0,
+			      USB4_SB_OPCODE_RUN_HW_LANE_MARGINING, 2500);
+	if (ret)
+		return ret;
+
+	return usb4_port_sb_read(port, USB4_SB_TARGET_ROUTER, 0,
+				 USB4_SB_DATA, results, sizeof(*results) * 2);
+}
+
+/**
+ * usb4_port_sw_margin() - Run software lane margining on port
+ * @port: USB4 port
+ * @lanes: Which lanes to run (must match the port capabilities). Can be
+ *	   %0, %1 or %7.
+ * @timing: Perform timing margining instead of voltage
+ * @right_high: Use Right/high margin instead of left/low
+ * @counter: What to do with the error counter
+ *
+ * Runs software lane margining on USB4 port. Read back the error
+ * counters by calling usb4_port_sw_margin_errors(). Returns %0 in
+ * success and negative errno otherwise.
+ */
+int usb4_port_sw_margin(struct tb_port *port, unsigned int lanes, bool timing,
+			bool right_high, u32 counter)
+{
+	u32 val;
+	int ret;
+
+	val = lanes;
+	if (timing)
+		val |= USB4_MARGIN_SW_TIME;
+	if (right_high)
+		val |= USB4_MARGIN_SW_RH;
+	val |= (counter << USB4_MARGIN_SW_COUNTER_SHIFT) &
+		USB4_MARGIN_SW_COUNTER_MASK;
+
+	ret = usb4_port_sb_write(port, USB4_SB_TARGET_ROUTER, 0,
+				 USB4_SB_METADATA, &val, sizeof(val));
+	if (ret)
+		return ret;
+
+	return usb4_port_sb_op(port, USB4_SB_TARGET_ROUTER, 0,
+			       USB4_SB_OPCODE_RUN_SW_LANE_MARGINING, 2500);
+}
+
+/**
+ * usb4_port_sw_margin_errors() - Read the software margining error counters
+ * @port: USB4 port
+ * @errors: Error metadata is copied here.
+ *
+ * This reads back the software margining error counters from the port.
+ * Returns %0 in success and negative errno otherwise.
+ */
+int usb4_port_sw_margin_errors(struct tb_port *port, u32 *errors)
+{
+	int ret;
+
+	ret = usb4_port_sb_op(port, USB4_SB_TARGET_ROUTER, 0,
+			      USB4_SB_OPCODE_READ_SW_MARGIN_ERR, 150);
+	if (ret)
+		return ret;
+
+	return usb4_port_sb_read(port, USB4_SB_TARGET_ROUTER, 0,
+				 USB4_SB_METADATA, errors, sizeof(*errors));
+}
+
 static inline int usb4_port_retimer_op(struct tb_port *port, u8 index,
 				       enum usb4_sb_opcode opcode,
 				       int timeout_msec)

drivers/thunderbolt/xdomain.c

@@ -1435,6 +1435,8 @@ static int tb_xdomain_get_properties(struct tb_xdomain *xd)
 		if (xd->vendor_name && xd->device_name)
 			dev_info(&xd->dev, "%s %s\n", xd->vendor_name,
 				 xd->device_name);
+
+		tb_xdomain_debugfs_init(xd);
 	} else {
 		kobject_uevent(&xd->dev.kobj, KOBJ_CHANGE);
 	}
@@ -1935,6 +1937,8 @@ static int unregister_service(struct device *dev, void *data)
  */
 void tb_xdomain_remove(struct tb_xdomain *xd)
 {
+	tb_xdomain_debugfs_remove(xd);
+
 	stop_handshake(xd);
 
 	device_for_each_child_reverse(&xd->dev, xd, unregister_service);