usbc_mux: Adding low power mode to USB MUX

This is useful when the PS8751 is used solely as a SS MUX and not a
TCPC. It will not get the normal low power mode commands from the PD
state machine. We need to issue separate low power command and
re-initialization for it. This CL is setting up the machinery for the
child CL that uses it for bip.

BRANCH=none
BUG=b:111664205,b:111876407
TEST=verify that lower power mode is issued for bip with CL stack along
with the reinitialization when exiting low power mode.

Change-Id: Ida09568acf1f353298520f75505f726d95309c57
Signed-off-by: Jett Rink <jettrink@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/1153834

1 files changed, 17 insertions, 5 deletions

diff --git a/include/usb_mux.h b/include/usb_mux.h
index 54107771ed..6a01aae3df 100644
--- a/include/usb_mux.h
+++ b/include/usb_mux.h
@@ -43,7 +43,8 @@ enum typec_mux {
 /* Mux driver function pointers */
 struct usb_mux_driver {
 	/**
-	 * Initialize USB mux.
+	 * Initialize USB mux. This is called every time the MUX is access after
+	 * being put in a fully disconnected state (low power mode).
 	 *
 	 * @param port_addr Port/address driver-defined parameter.
 	 * @return EC_SUCCESS on success, non-zero error code on failure.
@@ -76,13 +77,24 @@ struct usb_mux {
 	 * (for i2c muxes) or a port number (for GPIO 'muxes').
 	 */
 	const int port_addr;
+
 	/* Mux driver */
 	const struct usb_mux_driver *driver;
 
 	/**
-	 * Board specific initialization for USB mux that is
-	 * called after mux->driver->init() function and every time the port
-	 * leaves auto-toggle state.
+	 * Optional method that is called after the mux fully disconnects.
+	 *
+	 * Note: this method does not need to be defined for TCPC/MUX combos
+	 * where the TCPC is actively used since the PD state machine
+	 * will put the chip into lower power mode.
+	 *
+	 * @param mux USB mux to put into low power.
+	 * @return EC_SUCCESS on success, non-zero error code on failure.
+	 */
+	int (*enter_low_power_mode)(const struct usb_mux *mux);
+
+	/**
+	 * Optional method for tuning for USB mux during mux->driver->init().
 	 *
 	 * @param mux USB mux to tune
 	 * @return EC_SUCCESS on success, non-zero error code on failure.
@@ -113,7 +125,7 @@ extern struct usb_mux usb_muxes[];
 /**
  * Initialize USB mux to its default state.
  *
- * @param port  Port number.
+ * @param port Port number.
  */
 void usb_mux_init(int port);