usb: typec: tcpm: AMS and Collision Avoidance

This patch provides the implementation of Collision Avoidance introduced
in PD3.0. The start of each Atomic Message Sequence (AMS) initiated by
the port will be denied if the current AMS is not interruptible. The
Source port will set the CC to SinkTxNG if it is going to initiate an
AMS, and SinkTxOk otherwise. Meanwhile, any AMS initiated by a Sink port
will be denied in TCPM if the port partner (Source) sets SinkTxNG except
for HARD_RESET and SOFT_RESET.
Tested-by: Hans de Goede <hdegoede@redhat.com>
Reviewed-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Signed-off-by: Kyle Tso <kyletso@google.com>
Link: https://lore.kernel.org/r/20210114145053.1952756-2-kyletso@google.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

include/linux/usb/pd.h

@@ -479,6 +479,7 @@ static inline unsigned int rdo_max_power(u32 rdo)
 #define PD_T_NEWSRC		250	/* Maximum of 275ms */
 #define PD_T_SWAP_SRC_START	20	/* Minimum of 20ms */
 #define PD_T_BIST_CONT_MODE	50	/* 30 - 60 ms */
+#define PD_T_SINK_TX		16	/* 16 - 20 ms */
 
 #define PD_T_DRP_TRY		100	/* 75 - 150 ms */
 #define PD_T_DRP_TRYWAIT	600	/* 400 - 800 ms */

include/linux/usb/tcpm.h

@@ -19,6 +19,10 @@ enum typec_cc_status {
 	TYPEC_CC_RP_3_0,
 };
 
+/* Collision Avoidance */
+#define SINK_TX_NG	TYPEC_CC_RP_1_5
+#define SINK_TX_OK	TYPEC_CC_RP_3_0
+
 enum typec_cc_polarity {
 	TYPEC_POLARITY_CC1,
 	TYPEC_POLARITY_CC2,