feat(ti): synchronize access to secure proxy threads

When communicating with the system controller over secure proxy we clear
a thread, write our message, then wait for a response. This must not be
interrupted by a different transfer on the same thread. Take a lock
during this sequence to prevent contention.

Signed-off-by: Andrew Davis <afd@ti.com>
Change-Id: I7789f017fde7180ab6b4ac07458464b967c8e580

plat/ti/k3/common/drivers/ti_sci/ti_sci.c

@@ -13,6 +13,7 @@
 #include <string.h>
 
 #include <platform_def.h>
+#include <lib/bakery_lock.h>
 
 #include <common/debug.h>
 #include <sec_proxy.h>
@@ -25,6 +26,8 @@ __section(".tzfw_coherent_mem")
 #endif
 static uint8_t message_sequence;
 
+DEFINE_BAKERY_LOCK(ti_sci_xfer_lock);
+
 /**
  * struct ti_sci_xfer - Structure representing a message flow
  * @tx_message:	Transmit message
@@ -146,6 +149,8 @@ static int ti_sci_do_xfer(struct ti_sci_xfer *xfer)
 	struct k3_sec_proxy_msg *rx_msg = &xfer->rx_message;
 	int ret;
 
+	bakery_lock_get(&ti_sci_xfer_lock);
+
 	/* Clear any spurious messages in receive queue */
 	ret = k3_sec_proxy_clear_rx_thread(SP_RESPONSE);
 	if (ret) {
@@ -169,6 +174,8 @@ static int ti_sci_do_xfer(struct ti_sci_xfer *xfer)
 		}
 	}
 
+	bakery_lock_release(&ti_sci_xfer_lock);
+
 	return 0;
 }