usb: typec: API for controlling USB Type-C Multiplexers

USB Type-C connectors consist of various muxes and switches
that route the pins on the connector to the right locations.
The USB Type-C drivers need to be able to control the muxes,
as they are the ones that know things like the cable plug
orientation, and the current mode that was negotiated with
the partner.

This introduces a small API for registering and controlling
cable plug orientation switches, and separate small API for
registering and controlling pin multiplexer/demultiplexer
switches that are needed with Accessory/Alternate Modes.

Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 62 insertions, 11 deletions

diff --git a/Documentation/driver-api/usb/typec.rst b/Documentation/driver-api/usb/typec.rst
index 8a7249f2ff04..feb31946490b 100644
--- a/Documentation/driver-api/usb/typec.rst
+++ b/Documentation/driver-api/usb/typec.rst
@@ -61,7 +61,7 @@ Registering the ports
 The port drivers will describe every Type-C port they control with struct
 typec_capability data structure, and register them with the following API:
 
-.. kernel-doc:: drivers/usb/typec/typec.c
+.. kernel-doc:: drivers/usb/typec/class.c
    :functions: typec_register_port typec_unregister_port
 
 When registering the ports, the prefer_role member in struct typec_capability
@@ -80,7 +80,7 @@ typec_partner_desc. The class copies the details of the partner during
 registration. The class offers the following API for registering/unregistering
 partners.
 
-.. kernel-doc:: drivers/usb/typec/typec.c
+.. kernel-doc:: drivers/usb/typec/class.c
    :functions: typec_register_partner typec_unregister_partner
 
 The class will provide a handle to struct typec_partner if the registration was
@@ -92,7 +92,7 @@ should include handle to struct usb_pd_identity instance. The class will then
 create a sysfs directory for the identity under the partner device. The result
 of Discover Identity command can then be reported with the following API:
 
-.. kernel-doc:: drivers/usb/typec/typec.c
+.. kernel-doc:: drivers/usb/typec/class.c
    :functions: typec_partner_set_identity
 
 Registering Cables
@@ -113,7 +113,7 @@ typec_cable_desc and about a plug in struct typec_plug_desc. The class copies
 the details during registration. The class offers the following API for
 registering/unregistering cables and their plugs:
 
-.. kernel-doc:: drivers/usb/typec/typec.c
+.. kernel-doc:: drivers/usb/typec/class.c
    :functions: typec_register_cable typec_unregister_cable typec_register_plug typec_unregister_plug
 
 The class will provide a handle to struct typec_cable and struct typec_plug if
@@ -125,7 +125,7 @@ include handle to struct usb_pd_identity instance. The class will then create a
 sysfs directory for the identity under the cable device. The result of Discover
 Identity command can then be reported with the following API:
 
-.. kernel-doc:: drivers/usb/typec/typec.c
+.. kernel-doc:: drivers/usb/typec/class.c
    :functions: typec_cable_set_identity
 
 Notifications
@@ -135,7 +135,7 @@ When the partner has executed a role change, or when the default roles change
 during connection of a partner or cable, the port driver must use the following
 APIs to report it to the class:
 
-.. kernel-doc:: drivers/usb/typec/typec.c
+.. kernel-doc:: drivers/usb/typec/class.c
    :functions: typec_set_data_role typec_set_pwr_role typec_set_vconn_role typec_set_pwr_opmode
 
 Alternate Modes
@@ -150,7 +150,7 @@ and struct typec_altmode_desc which is a container for all the supported modes.
 Ports that support Alternate Modes need to register each SVID they support with
 the following API:
 
-.. kernel-doc:: drivers/usb/typec/typec.c
+.. kernel-doc:: drivers/usb/typec/class.c
    :functions: typec_port_register_altmode
 
 If a partner or cable plug provides a list of SVIDs as response to USB Power
@@ -159,12 +159,12 @@ registered.
 
 API for the partners:
 
-.. kernel-doc:: drivers/usb/typec/typec.c
+.. kernel-doc:: drivers/usb/typec/class.c
    :functions: typec_partner_register_altmode
 
 API for the Cable Plugs:
 
-.. kernel-doc:: drivers/usb/typec/typec.c
+.. kernel-doc:: drivers/usb/typec/class.c
    :functions: typec_plug_register_altmode
 
 So ports, partners and cable plugs will register the alternate modes with their
@@ -172,11 +172,62 @@ own functions, but the registration will always return a handle to struct
 typec_altmode on success, or NULL. The unregistration will happen with the same
 function:
 
-.. kernel-doc:: drivers/usb/typec/typec.c
+.. kernel-doc:: drivers/usb/typec/class.c
    :functions: typec_unregister_altmode
 
 If a partner or cable plug enters or exits a mode, the port driver needs to
 notify the class with the following API:
 
-.. kernel-doc:: drivers/usb/typec/typec.c
+.. kernel-doc:: drivers/usb/typec/class.c
    :functions: typec_altmode_update_active
+
+Multiplexer/DeMultiplexer Switches
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+USB Type-C connectors may have one or more mux/demux switches behind them. Since
+the plugs can be inserted right-side-up or upside-down, a switch is needed to
+route the correct data pairs from the connector to the USB controllers. If
+Alternate or Accessory Modes are supported, another switch is needed that can
+route the pins on the connector to some other component besides USB. USB Type-C
+Connector Class supplies an API for registering those switches.
+
+.. kernel-doc:: drivers/usb/typec/mux.c
+   :functions: typec_switch_register typec_switch_unregister typec_mux_register typec_mux_unregister
+
+In most cases the same physical mux will handle both the orientation and mode.
+However, as the port drivers will be responsible for the orientation, and the
+alternate mode drivers for the mode, the two are always separated into their
+own logical components: "mux" for the mode and "switch" for the orientation.
+
+When a port is registered, USB Type-C Connector Class requests both the mux and
+the switch for the port. The drivers can then use the following API for
+controlling them:
+
+.. kernel-doc:: drivers/usb/typec/class.c
+   :functions: typec_set_orientation typec_set_mode
+
+If the connector is dual-role capable, there may also be a switch for the data
+role. USB Type-C Connector Class does not supply separate API for them. The
+port drivers can use USB Role Class API with those.
+
+Illustration of the muxes behind a connector that supports an alternate mode:
+
+                     ------------------------
+                     |       Connector      |
+                     ------------------------
+                            |         |
+                     ------------------------
+                      \     Orientation    /
+                       --------------------
+                                |
+                       --------------------
+                      /        Mode        \
+                     ------------------------
+                         /              \
+      ------------------------        --------------------
+      |       Alt Mode       |       /      USB Role      \
+      ------------------------      ------------------------
+                                         /            \
+                     ------------------------      ------------------------
+                     |       USB Host       |      |       USB Device     |
+                     ------------------------      ------------------------