usb: typec: Add attribute file showing the USB Modes of the partner

This attribute file shows the supported USB modes (USB 2.0,
USB 3.0 and USB4) of the partner, and the currently active
mode.

The active mode is determined primarily by checking the
speed of the enumerated USB device. When USB Power Delivery
is supported, the active USB mode should be always the mode
that was used with the Enter_USB Message, regardless of the
result of the USB enumeration. The port drivers can
separately assign the mode with a dedicated API.

If USB Power Delivery Identity is supplied for the partner
device, the supported modes are extracted from it.

Signed-off-by: Heikki Krogerus <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

Documentation/ABI/testing/sysfs-class-typec

···
 		directory exists, it will have an attribute file for every VDO
 		in Discover Identity command result.
 
+What:		/sys/class/typec/<port>-partner/usb_mode
+Date:		November 2024
+Contact:	Heikki Krogerus <[e-mail]>
+Description:	The USB Modes that the partner device supports. The active mode
+		is displayed in brackets. The active USB mode can be changed by
+		writing to this file when the port driver is able to send Data
+		Reset Message to the partner. That requires USB Power Delivery
+		contract between the partner and the port.
+
+		Valid values:
+		- usb2 (USB 2.0)
+		- usb3 (USB 3.2)
+		- usb4 (USB4)
+
 USB Type-C cable devices (eg. /sys/class/typec/port0-cable/)
 
 Note: Electronically Marked Cables will have a device also for one cable plug

drivers/usb/typec/class.c

···
 /* ------------------------------------------------------------------------- */
 /* Type-C Partners */
 
+/**
+ * typec_partner_set_usb_mode - Assign active USB Mode for the partner
+ * @partner: USB Type-C partner
+ * @mode: USB Mode (USB2, USB3 or USB4)
+ *
+ * The port drivers can use this function to assign the active USB Mode to
+ * @partner. The USB Mode can change for example due to Data Reset.
+ */
+void typec_partner_set_usb_mode(struct typec_partner *partner, enum usb_mode mode)
+{
+	if (!partner || partner->usb_mode == mode)
+		return;
+
+	partner->usb_capability |= BIT(mode - 1);
+	partner->usb_mode = mode;
+	sysfs_notify(&partner->dev.kobj, NULL, "usb_mode");
+}
+EXPORT_SYMBOL_GPL(typec_partner_set_usb_mode);
+
+static ssize_t
+usb_mode_show(struct device *dev, struct device_attribute *attr, char *buf)
+{
+	struct typec_partner *partner = to_typec_partner(dev);
+	int len = 0;
+	int i;
+
+	for (i = USB_MODE_USB2; i < USB_MODE_USB4 + 1; i++) {
+		if (!(BIT(i - 1) & partner->usb_capability))
+			continue;
+
+		if (i == partner->usb_mode)
+			len += sysfs_emit_at(buf, len, "[%s] ", usb_modes[i]);
+		else
+			len += sysfs_emit_at(buf, len, "%s ", usb_modes[i]);
+	}
+
+	sysfs_emit_at(buf, len - 1, "\n");
+
+	return len;
+}
+
+static ssize_t usb_mode_store(struct device *dev, struct device_attribute *attr,
+			      const char *buf, size_t size)
+{
+	struct typec_partner *partner = to_typec_partner(dev);
+	struct typec_port *port = to_typec_port(dev->parent);
+	int mode;
+	int ret;
+
+	if (!port->ops || !port->ops->enter_usb_mode)
+		return -EOPNOTSUPP;
+
+	mode = sysfs_match_string(usb_modes, buf);
+	if (mode < 0)
+		return mode;
+
+	if (mode == partner->usb_mode)
+		return size;
+
+	ret = port->ops->enter_usb_mode(port, mode);
+	if (ret)
+		return ret;
+
+	typec_partner_set_usb_mode(partner, mode);
+
+	return size;
+}
+static DEVICE_ATTR_RW(usb_mode);
+
 static ssize_t accessory_mode_show(struct device *dev,
 				   struct device_attribute *attr,
 				   char *buf)
···
 	&dev_attr_supports_usb_power_delivery.attr,
 	&dev_attr_number_of_alternate_modes.attr,
 	&dev_attr_type.attr,
+	&dev_attr_usb_mode.attr,
 	&dev_attr_usb_power_delivery_revision.attr,
 	NULL
 };
···
 static umode_t typec_partner_attr_is_visible(struct kobject *kobj, struct attribute *attr, int n)
 {
 	struct typec_partner *partner = to_typec_partner(kobj_to_dev(kobj));
+	struct typec_port *port = to_typec_port(partner->dev.parent);
+
+	if (attr == &dev_attr_usb_mode.attr) {
+		if (!partner->usb_capability)
+			return 0;
+		if (!port->ops || !port->ops->enter_usb_mode)
+			return 0444;
+	}
 
 	if (attr == &dev_attr_number_of_alternate_modes.attr) {
 		if (partner->num_altmodes < 0)
···
  */
 int typec_partner_set_identity(struct typec_partner *partner)
 {
-	if (!partner->identity)
+	u8 usb_capability = partner->usb_capability;
+	struct device *dev = &partner->dev;
+	struct usb_pd_identity *id;
+
+	id = get_pd_identity(dev);
+	if (!id)
 		return -EINVAL;
 
-	typec_report_identity(&partner->dev);
+	if (to_typec_port(dev->parent)->data_role == TYPEC_HOST)  {
+		u32 devcap = PD_VDO_UFP_DEVCAP(id->vdo[0]);
+
+		if (devcap & (DEV_USB2_CAPABLE | DEV_USB2_BILLBOARD))
+			usb_capability |= USB_CAPABILITY_USB2;
+		if (devcap & DEV_USB3_CAPABLE)
+			usb_capability |= USB_CAPABILITY_USB3;
+		if (devcap & DEV_USB4_CAPABLE)
+			usb_capability |= USB_CAPABILITY_USB4;
+	} else {
+		usb_capability = PD_VDO_DFP_HOSTCAP(id->vdo[0]);
+	}
+
+	if (partner->usb_capability != usb_capability) {
+		partner->usb_capability = usb_capability;
+		sysfs_notify(&dev->kobj, NULL, "usb_mode");
+	}
+
+	typec_report_identity(dev);
 	return 0;
 }
 EXPORT_SYMBOL_GPL(typec_partner_set_identity);
···
 	partner->usb_pd = desc->usb_pd;
 	partner->accessory = desc->accessory;
 	partner->num_altmodes = -1;
+	partner->usb_capability = desc->usb_capability;
 	partner->pd_revision = desc->pd_revision;
 	partner->svdm_version = port->cap->svdm_version;
 	partner->attach = desc->attach;
···
 	partner->dev.parent = &port->dev;
 	partner->dev.type = &typec_partner_dev_type;
 	dev_set_name(&partner->dev, "%s-partner", dev_name(&port->dev));
+
+	if (port->usb2_dev) {
+		partner->usb_capability |= USB_CAPABILITY_USB2;
+		partner->usb_mode = USB_MODE_USB2;
+	}
+	if (port->usb3_dev) {
+		partner->usb_capability |= USB_CAPABILITY_USB2 | USB_CAPABILITY_USB3;
+		partner->usb_mode = USB_MODE_USB3;
+	}
 
 	ret = device_register(&partner->dev);
 	if (ret) {
···
 	struct typec_port *port = container_of(con, struct typec_port, con);
 	struct typec_partner *partner = typec_get_partner(port);
 	struct usb_device *udev = to_usb_device(dev);
+	enum usb_mode usb_mode;
 
-	if (udev->speed < USB_SPEED_SUPER)
+	if (udev->speed < USB_SPEED_SUPER) {
+		usb_mode = USB_MODE_USB2;
 		port->usb2_dev = dev;
-	else
+	} else {
+		usb_mode = USB_MODE_USB3;
 		port->usb3_dev = dev;
+	}
 
 	if (partner) {
+		typec_partner_set_usb_mode(partner, usb_mode);
 		typec_partner_link_device(partner, dev);
 		put_device(&partner->dev);
 	}

drivers/usb/typec/class.h

···
 	int				num_altmodes;
 	u16				pd_revision; /* 0300H = "3.0" */
 	enum usb_pd_svdm_ver		svdm_version;
+	enum usb_mode			usb_mode;
+	u8				usb_capability;
 
 	struct usb_power_delivery	*pd;
 

include/linux/usb/typec.h

···
  * @accessory: Audio, Debug or none.
  * @identity: Discover Identity command data
  * @pd_revision: USB Power Delivery Specification Revision if supported
+ * @usb_capability: Supported USB Modes
  * @attach: Notification about attached USB device
  * @deattach: Notification about removed USB device
  *
···
 	enum typec_accessory	accessory;
 	struct usb_pd_identity	*identity;
 	u16			pd_revision; /* 0300H = "3.0" */
+	u8			usb_capability;
 
 	void (*attach)(struct typec_partner *partner, struct device *dev);
 	void (*deattach)(struct typec_partner *partner, struct device *dev);
···
  * @pd_get: Get available USB Power Delivery Capabilities.
  * @pd_set: Set USB Power Delivery Capabilities.
  * @default_usb_mode_set: USB Mode to be used by default with Enter_USB Message
+ * @enter_usb_mode: Change the active USB Mode
  */
 struct typec_operations {
 	int (*try_role)(struct typec_port *port, int role);
···
 	struct usb_power_delivery **(*pd_get)(struct typec_port *port);
 	int (*pd_set)(struct typec_port *port, struct usb_power_delivery *pd);
 	int (*default_usb_mode_set)(struct typec_port *port, enum usb_mode mode);
+	int (*enter_usb_mode)(struct typec_port *port, enum usb_mode mode);
 };
 
 enum usb_pd_svdm_ver {
···
 int typec_partner_set_usb_power_delivery(struct typec_partner *partner,
 					 struct usb_power_delivery *pd);
 
+void typec_partner_set_usb_mode(struct typec_partner *partner, enum usb_mode usb_mode);
 void typec_port_set_usb_mode(struct typec_port *port, enum usb_mode mode);
 
 /**