usb: typec: tcpm: Add support for Sink Fast Role SWAP(FRS)

PD 3.0 spec defines a new mechanism for power role swap called
Fast role swap. This change enables TCPM to support FRS when
acting as sink.

Once the explicit contract is negotiated, sink port is
expected to query the source port for sink caps to
determine whether the source is FRS capable.
Bits 23 & 24 of fixed pdo of the sink caps from the source, when
set, indicates the current needed by the source when fast role
swap is in progress(Implicit contract phasae). 0 indicates that
the source does not support Fast Role Swap.

Upon receiving the FRS signal from the source,
TCPC(TCPM_FRS_EVENT) informs TCPM to start the Fast role swap sequence.

1. TCPM sends FRS PD message: FR_SWAP_SEND
2. If response is not received within the expiry of
   SenderResponseTimer, Error recovery is triggered.:
   FR_SWAP_SEND_TIMEOUT
3. Upon receipt of the accept message, TCPM waits for
   PSSourceOffTimer for PS_READY message from the partner:
   FR_SWAP_SNK_SRC_NEW_SINK_READY.

TCPC is expected to autonomously turn on vbus once the FRS
signal is received and vbus voltage falls below vsafe5v within
tSrcFrSwap. This is different from traditional power role swap
where the vbus sourcing is turned on by TCPM.

4. By this time, TCPC most likely would have started to
   source vbus, TCPM waits for tSrcFrSwap to see  if the
   lower level TCPC driver signals TCPM_SOURCING_VBUS event:
   FR_SWAP_SNK_SRC_SOURCE_VBUS_APPLIED.
5. When TCPC signals sourcing vbus, TCPM sends PS_READY msg and
   changes the CC pin from Rd to Rp. This is the end of fast
   role swap sequence and TCPM initiates the sequnce to negotiate
   explicit contract by transitioning into SRC_STARTUP after
   SwapSrcStart.

The code is written based on the sequence described in "Figure 8-107:
Dual-role Port in Sink to Source Fast Role Swap State Diagram" of
USB Power Delivery Specification Revision 3.0, Version 1.2.

Signed-off-by: Badhri Jagan Sridharan <badhri@google.com>
Reviewed-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Link: https://lore.kernel.org/r/20201008061556.1402293-7-badhri@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 7 insertions, 1 deletions

diff --git a/include/linux/usb/tcpm.h b/include/linux/usb/tcpm.h
index 89f58760cf48..09762d26fa0c 100644
--- a/include/linux/usb/tcpm.h
+++ b/include/linux/usb/tcpm.h
@@ -78,8 +78,11 @@ enum tcpm_transmit_type {
  *		automatically if a connection is established.
  * @try_role:	Optional; called to set a preferred role
  * @pd_transmit:Called to transmit PD message
- * @mux:	Pointer to multiplexer data
  * @set_bist_data: Turn on/off bist data mode for compliance testing
+ * @enable_frs:
+ *		Optional; Called to enable/disable PD 3.0 fast role swap.
+ *		Enabling frs is accessory dependent as not all PD3.0
+ *		accessories support fast role swap.
  */
 struct tcpc_dev {
 	struct fwnode_handle *fwnode;
@@ -105,6 +108,7 @@ struct tcpc_dev {
 	int (*pd_transmit)(struct tcpc_dev *dev, enum tcpm_transmit_type type,
 			   const struct pd_message *msg);
 	int (*set_bist_data)(struct tcpc_dev *dev, bool on);
+	int (*enable_frs)(struct tcpc_dev *dev, bool enable);
 };
 
 struct tcpm_port;
@@ -114,6 +118,8 @@ void tcpm_unregister_port(struct tcpm_port *port);
 
 void tcpm_vbus_change(struct tcpm_port *port);
 void tcpm_cc_change(struct tcpm_port *port);
+void tcpm_sink_frs(struct tcpm_port *port);
+void tcpm_sourcing_vbus(struct tcpm_port *port);
 void tcpm_pd_receive(struct tcpm_port *port,
 		     const struct pd_message *msg);
 void tcpm_pd_transmit_complete(struct tcpm_port *port,