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.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

include/linux/usb/pd.h

@@ -219,14 +219,16 @@ enum pd_pdo_type {
 #define PDO_CURR_MASK		0x3ff
 #define PDO_PWR_MASK		0x3ff
 
-#define PDO_FIXED_DUAL_ROLE	BIT(29)	/* Power role swap supported */
-#define PDO_FIXED_SUSPEND	BIT(28) /* USB Suspend supported (Source) */
-#define PDO_FIXED_HIGHER_CAP	BIT(28) /* Requires more than vSafe5V (Sink) */
-#define PDO_FIXED_EXTPOWER	BIT(27) /* Externally powered */
-#define PDO_FIXED_USB_COMM	BIT(26) /* USB communications capable */
-#define PDO_FIXED_DATA_SWAP	BIT(25) /* Data role swap supported */
-#define PDO_FIXED_VOLT_SHIFT	10	/* 50mV units */
-#define PDO_FIXED_CURR_SHIFT	0	/* 10mA units */
+#define PDO_FIXED_DUAL_ROLE		BIT(29)	/* Power role swap supported */
+#define PDO_FIXED_SUSPEND		BIT(28) /* USB Suspend supported (Source) */
+#define PDO_FIXED_HIGHER_CAP		BIT(28) /* Requires more than vSafe5V (Sink) */
+#define PDO_FIXED_EXTPOWER		BIT(27) /* Externally powered */
+#define PDO_FIXED_USB_COMM		BIT(26) /* USB communications capable */
+#define PDO_FIXED_DATA_SWAP		BIT(25) /* Data role swap supported */
+#define PDO_FIXED_FRS_CURR_MASK		(BIT(24) | BIT(23)) /* FR_Swap Current (Sink) */
+#define PDO_FIXED_FRS_CURR_SHIFT	23
+#define PDO_FIXED_VOLT_SHIFT		10	/* 50mV units */
+#define PDO_FIXED_CURR_SHIFT		0	/* 10mA units */
 
 #define PDO_FIXED_VOLT(mv)	((((mv) / 50) & PDO_VOLT_MASK) << PDO_FIXED_VOLT_SHIFT)
 #define PDO_FIXED_CURR(ma)	((((ma) / 10) & PDO_CURR_MASK) << PDO_FIXED_CURR_SHIFT)
@@ -454,6 +456,7 @@ static inline unsigned int rdo_max_power(u32 rdo)
 #define PD_T_DB_DETECT		10000	/* 10 - 15 seconds */
 #define PD_T_SEND_SOURCE_CAP	150	/* 100 - 200 ms */
 #define PD_T_SENDER_RESPONSE	60	/* 24 - 30 ms, relaxed */
+#define PD_T_RECEIVER_RESPONSE	15	/* 15ms max */
 #define PD_T_SOURCE_ACTIVITY	45
 #define PD_T_SINK_ACTIVITY	135
 #define PD_T_SINK_WAIT_CAP	240

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,