usb: typec: Add driver for Thunderbolt 3 Alternate Mode

Thunderbolt 3 Alternate Mode entry flow is described in
USB Type-C Specification Release 2.0.

Signed-off-by: Heikki Krogerus <[e-mail]>
Co-developed-by: Abhishek Pandit-Subedi <[e-mail]>
Signed-off-by: Abhishek Pandit-Subedi <[e-mail]>
Reviewed-by: Benson Leung <[e-mail]>
Link: https://lore.kernel.org/r/20241213153543.v5.2.I3080b036e8de0b9957c57c1c3059db7149c5e549@changeid
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/usb/typec/altmodes/Kconfig

···
 	  To compile this driver as a module, choose M here: the
 	  module will be called typec_nvidia.
 
+config TYPEC_TBT_ALTMODE
+	tristate "Thunderbolt3 Alternate Mode driver"
+	help
+	  Select this option if you have Thunderbolt3 hardware on your
+	  system.
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called typec_thunderbolt.
+
 endmenu

drivers/usb/typec/altmodes/Makefile

···
 typec_displayport-y			:= displayport.o
 obj-$(CONFIG_TYPEC_NVIDIA_ALTMODE)	+= typec_nvidia.o
 typec_nvidia-y				:= nvidia.o
+obj-$(CONFIG_TYPEC_TBT_ALTMODE)		+= typec_thunderbolt.o
+typec_thunderbolt-y			:= thunderbolt.o

drivers/usb/typec/altmodes/thunderbolt.c

···
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * USB Typec-C Thunderbolt3 Alternate Mode driver
+ *
+ * Copyright (C) 2019 Intel Corporation
+ * Author: Heikki Krogerus <[e-mail]>
+ */
+
+#include <linux/lockdep.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/workqueue.h>
+#include <linux/usb/pd_vdo.h>
+#include <linux/usb/typec_altmode.h>
+#include <linux/usb/typec_tbt.h>
+
+enum tbt_state {
+	TBT_STATE_IDLE,
+	TBT_STATE_SOP_P_ENTER,
+	TBT_STATE_SOP_PP_ENTER,
+	TBT_STATE_ENTER,
+	TBT_STATE_EXIT,
+	TBT_STATE_SOP_PP_EXIT,
+	TBT_STATE_SOP_P_EXIT
+};
+
+struct tbt_altmode {
+	enum tbt_state state;
+	struct typec_cable *cable;
+	struct typec_altmode *alt;
+	struct typec_altmode *plug[2];
+	u32 enter_vdo;
+
+	struct work_struct work;
+	struct mutex lock; /* device lock */
+};
+
+static bool tbt_ready(struct typec_altmode *alt);
+
+static int tbt_enter_mode(struct tbt_altmode *tbt)
+{
+	struct typec_altmode *plug = tbt->plug[TYPEC_PLUG_SOP_P];
+	u32 vdo;
+
+	vdo = tbt->alt->vdo & (TBT_VENDOR_SPECIFIC_B0 | TBT_VENDOR_SPECIFIC_B1);
+	vdo |= tbt->alt->vdo & TBT_INTEL_SPECIFIC_B0;
+	vdo |= TBT_MODE;
+
+	if (plug) {
+		if (typec_cable_is_active(tbt->cable))
+			vdo |= TBT_ENTER_MODE_ACTIVE_CABLE;
+
+		vdo |= TBT_ENTER_MODE_CABLE_SPEED(TBT_CABLE_SPEED(plug->vdo));
+		vdo |= plug->vdo & TBT_CABLE_ROUNDED;
+		vdo |= plug->vdo & TBT_CABLE_OPTICAL;
+		vdo |= plug->vdo & TBT_CABLE_RETIMER;
+		vdo |= plug->vdo & TBT_CABLE_LINK_TRAINING;
+	} else {
+		vdo |= TBT_ENTER_MODE_CABLE_SPEED(TBT_CABLE_USB3_PASSIVE);
+	}
+
+	tbt->enter_vdo = vdo;
+	return typec_altmode_enter(tbt->alt, &vdo);
+}
+
+static void tbt_altmode_work(struct work_struct *work)
+{
+	struct tbt_altmode *tbt = container_of(work, struct tbt_altmode, work);
+	int ret;
+
+	mutex_lock(&tbt->lock);
+
+	switch (tbt->state) {
+	case TBT_STATE_SOP_P_ENTER:
+		ret = typec_cable_altmode_enter(tbt->alt, TYPEC_PLUG_SOP_P, NULL);
+		if (ret) {
+			dev_dbg(&tbt->plug[TYPEC_PLUG_SOP_P]->dev,
+				"failed to enter mode (%d)\n", ret);
+			goto disable_plugs;
+		}
+		break;
+	case TBT_STATE_SOP_PP_ENTER:
+		ret = typec_cable_altmode_enter(tbt->alt, TYPEC_PLUG_SOP_PP,  NULL);
+		if (ret) {
+			dev_dbg(&tbt->plug[TYPEC_PLUG_SOP_PP]->dev,
+				"failed to enter mode (%d)\n", ret);
+			goto disable_plugs;
+		}
+		break;
+	case TBT_STATE_ENTER:
+		ret = tbt_enter_mode(tbt);
+		if (ret)
+			dev_dbg(&tbt->alt->dev, "failed to enter mode (%d)\n",
+				ret);
+		break;
+	case TBT_STATE_EXIT:
+		typec_altmode_exit(tbt->alt);
+		break;
+	case TBT_STATE_SOP_PP_EXIT:
+		typec_cable_altmode_exit(tbt->alt, TYPEC_PLUG_SOP_PP);
+		break;
+	case TBT_STATE_SOP_P_EXIT:
+		typec_cable_altmode_exit(tbt->alt, TYPEC_PLUG_SOP_P);
+		break;
+	default:
+		break;
+	}
+
+	tbt->state = TBT_STATE_IDLE;
+
+	mutex_unlock(&tbt->lock);
+	return;
+
+disable_plugs:
+	for (int i = TYPEC_PLUG_SOP_PP; i > 0; --i) {
+		if (tbt->plug[i])
+			typec_altmode_put_plug(tbt->plug[i]);
+
+		tbt->plug[i] = NULL;
+	}
+
+	tbt->state = TBT_STATE_ENTER;
+	schedule_work(&tbt->work);
+	mutex_unlock(&tbt->lock);
+}
+
+/*
+ * If SOP' is available, enter that first (which will trigger a VDM response
+ * that will enter SOP" if available and then the port). If entering SOP' fails,
+ * stop attempting to enter either cable altmode (probably not supported) and
+ * directly enter the port altmode.
+ */
+static int tbt_enter_modes_ordered(struct typec_altmode *alt)
+{
+	struct tbt_altmode *tbt = typec_altmode_get_drvdata(alt);
+	int ret = 0;
+
+	lockdep_assert_held(&tbt->lock);
+
+	if (!tbt_ready(tbt->alt))
+		return -ENODEV;
+
+	if (tbt->plug[TYPEC_PLUG_SOP_P]) {
+		ret = typec_cable_altmode_enter(alt, TYPEC_PLUG_SOP_P, NULL);
+		if (ret < 0) {
+			for (int i = TYPEC_PLUG_SOP_PP; i > 0; --i) {
+				if (tbt->plug[i])
+					typec_altmode_put_plug(tbt->plug[i]);
+
+				tbt->plug[i] = NULL;
+			}
+		} else {
+			return ret;
+		}
+	}
+
+	return tbt_enter_mode(tbt);
+}
+
+static int tbt_cable_altmode_vdm(struct typec_altmode *alt,
+				 enum typec_plug_index sop, const u32 hdr,
+				 const u32 *vdo, int count)
+{
+	struct tbt_altmode *tbt = typec_altmode_get_drvdata(alt);
+	int cmd_type = PD_VDO_CMDT(hdr);
+	int cmd = PD_VDO_CMD(hdr);
+
+	mutex_lock(&tbt->lock);
+
+	if (tbt->state != TBT_STATE_IDLE) {
+		mutex_unlock(&tbt->lock);
+		return -EBUSY;
+	}
+
+	switch (cmd_type) {
+	case CMDT_RSP_ACK:
+		switch (cmd) {
+		case CMD_ENTER_MODE:
+			/*
+			 * Following the order described in USB Type-C Spec
+			 * R2.0 Section 6.7.3: SOP', SOP", then port.
+			 */
+			if (sop == TYPEC_PLUG_SOP_P) {
+				if (tbt->plug[TYPEC_PLUG_SOP_PP])
+					tbt->state = TBT_STATE_SOP_PP_ENTER;
+				else
+					tbt->state = TBT_STATE_ENTER;
+			} else if (sop == TYPEC_PLUG_SOP_PP)
+				tbt->state = TBT_STATE_ENTER;
+
+			break;
+		case CMD_EXIT_MODE:
+			/* Exit in opposite order: Port, SOP", then SOP'. */
+			if (sop == TYPEC_PLUG_SOP_PP)
+				tbt->state = TBT_STATE_SOP_P_EXIT;
+			break;
+		}
+		break;
+	default:
+		break;
+	}
+
+	if (tbt->state != TBT_STATE_IDLE)
+		schedule_work(&tbt->work);
+
+	mutex_unlock(&tbt->lock);
+	return 0;
+}
+
+static int tbt_altmode_vdm(struct typec_altmode *alt,
+			   const u32 hdr, const u32 *vdo, int count)
+{
+	struct tbt_altmode *tbt = typec_altmode_get_drvdata(alt);
+	struct typec_thunderbolt_data data;
+	int cmd_type = PD_VDO_CMDT(hdr);
+	int cmd = PD_VDO_CMD(hdr);
+
+	mutex_lock(&tbt->lock);
+
+	if (tbt->state != TBT_STATE_IDLE) {
+		mutex_unlock(&tbt->lock);
+		return -EBUSY;
+	}
+
+	switch (cmd_type) {
+	case CMDT_RSP_ACK:
+		/* Port altmode is last to enter and first to exit. */
+		switch (cmd) {
+		case CMD_ENTER_MODE:
+			memset(&data, 0, sizeof(data));
+
+			data.device_mode = tbt->alt->vdo;
+			data.enter_vdo = tbt->enter_vdo;
+			if (tbt->plug[TYPEC_PLUG_SOP_P])
+				data.cable_mode = tbt->plug[TYPEC_PLUG_SOP_P]->vdo;
+
+			typec_altmode_notify(alt, TYPEC_STATE_MODAL, &data);
+			break;
+		case CMD_EXIT_MODE:
+			if (tbt->plug[TYPEC_PLUG_SOP_PP])
+				tbt->state = TBT_STATE_SOP_PP_EXIT;
+			else if (tbt->plug[TYPEC_PLUG_SOP_P])
+				tbt->state = TBT_STATE_SOP_P_EXIT;
+			break;
+		}
+		break;
+	case CMDT_RSP_NAK:
+		switch (cmd) {
+		case CMD_ENTER_MODE:
+			dev_warn(&alt->dev, "Enter Mode refused\n");
+			break;
+		default:
+			break;
+		}
+		break;
+	default:
+		break;
+	}
+
+	if (tbt->state != TBT_STATE_IDLE)
+		schedule_work(&tbt->work);
+
+	mutex_unlock(&tbt->lock);
+
+	return 0;
+}
+
+static int tbt_altmode_activate(struct typec_altmode *alt, int activate)
+{
+	struct tbt_altmode *tbt = typec_altmode_get_drvdata(alt);
+	int ret;
+
+	mutex_lock(&tbt->lock);
+
+	if (activate)
+		ret = tbt_enter_modes_ordered(alt);
+	else
+		ret = typec_altmode_exit(alt);
+
+	mutex_unlock(&tbt->lock);
+
+	return ret;
+}
+
+static const struct typec_altmode_ops tbt_altmode_ops = {
+	.vdm		= tbt_altmode_vdm,
+	.activate	= tbt_altmode_activate
+};
+
+static const struct typec_cable_ops tbt_cable_ops = {
+	.vdm		= tbt_cable_altmode_vdm,
+};
+
+static int tbt_altmode_probe(struct typec_altmode *alt)
+{
+	struct tbt_altmode *tbt;
+
+	tbt = devm_kzalloc(&alt->dev, sizeof(*tbt), GFP_KERNEL);
+	if (!tbt)
+		return -ENOMEM;
+
+	INIT_WORK(&tbt->work, tbt_altmode_work);
+	mutex_init(&tbt->lock);
+	tbt->alt = alt;
+
+	alt->desc = "Thunderbolt3";
+	typec_altmode_set_drvdata(alt, tbt);
+	typec_altmode_set_ops(alt, &tbt_altmode_ops);
+
+	if (tbt_ready(alt)) {
+		if (tbt->plug[TYPEC_PLUG_SOP_P])
+			tbt->state = TBT_STATE_SOP_P_ENTER;
+		else if (tbt->plug[TYPEC_PLUG_SOP_PP])
+			tbt->state = TBT_STATE_SOP_PP_ENTER;
+		else
+			tbt->state = TBT_STATE_ENTER;
+		schedule_work(&tbt->work);
+	}
+
+	return 0;
+}
+
+static void tbt_altmode_remove(struct typec_altmode *alt)
+{
+	struct tbt_altmode *tbt = typec_altmode_get_drvdata(alt);
+
+	for (int i = TYPEC_PLUG_SOP_PP; i > 0; --i) {
+		if (tbt->plug[i])
+			typec_altmode_put_plug(tbt->plug[i]);
+	}
+
+	if (tbt->cable)
+		typec_cable_put(tbt->cable);
+}
+
+static bool tbt_ready(struct typec_altmode *alt)
+{
+	struct tbt_altmode *tbt = typec_altmode_get_drvdata(alt);
+	struct typec_altmode *plug;
+
+	if (tbt->cable)
+		return true;
+
+	/* Thunderbolt 3 requires a cable with eMarker */
+	tbt->cable = typec_cable_get(typec_altmode2port(tbt->alt));
+	if (!tbt->cable)
+		return false;
+
+	/* We accept systems without SOP' or SOP''. This means the port altmode
+	 * driver will be responsible for properly ordering entry/exit.
+	 */
+	for (int i = 0; i < TYPEC_PLUG_SOP_PP + 1; i++) {
+		plug = typec_altmode_get_plug(tbt->alt, i);
+		if (IS_ERR(plug))
+			continue;
+
+		if (!plug || plug->svid != USB_TYPEC_TBT_SID)
+			break;
+
+		plug->desc = "Thunderbolt3";
+		plug->cable_ops = &tbt_cable_ops;
+		typec_altmode_set_drvdata(plug, tbt);
+
+		tbt->plug[i] = plug;
+	}
+
+	return true;
+}
+
+static const struct typec_device_id tbt_typec_id[] = {
+	{ USB_TYPEC_TBT_SID },
+	{ }
+};
+MODULE_DEVICE_TABLE(typec, tbt_typec_id);
+
+static struct typec_altmode_driver tbt_altmode_driver = {
+	.id_table = tbt_typec_id,
+	.probe = tbt_altmode_probe,
+	.remove = tbt_altmode_remove,
+	.driver = {
+		.name = "typec-thunderbolt",
+	}
+};
+module_typec_altmode_driver(tbt_altmode_driver);
+
+MODULE_AUTHOR("Heikki Krogerus <[e-mail]>");
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("Thunderbolt3 USB Type-C Alternate Mode");

include/linux/usb/typec_tbt.h

···
 
 #define   TBT_GEN3_NON_ROUNDED                 0
 #define   TBT_GEN3_GEN4_ROUNDED_NON_ROUNDED    1
+#define TBT_CABLE_ROUNDED		BIT(19)
 #define TBT_CABLE_OPTICAL		BIT(21)
 #define TBT_CABLE_RETIMER		BIT(22)
 #define TBT_CABLE_LINK_TRAINING		BIT(23)