ipc: add cache flushing and invalidation for IPC data

This patch addresses an issue with incorrect IPC responses due to the
lack of cache flushing and invalidation on secondary cores.

The following changes have been made:

1. Added cache writeback for IPC message data in `ipc_msg_send` when the
   current core is not the primary core.
2. Added cache invalidation for IPC message data in
   `ipc_prepare_to_send` before writing to the mailbox.

These changes ensure that the IPC data is correctly synchronized between
cores.

Signed-off-by: Tomasz Leman <[email protected]>

src/include/sof/ipc/msg.h

@@ -35,6 +35,7 @@ struct ipc_msg {
 	uint32_t extension;	/* extension specific to platform */
 	uint32_t tx_size;	/* payload size in bytes */
 	void *tx_data;		/* pointer to payload data */
+	bool is_shared;		/* the message is shared cross-core */
 	struct list_item list;
 };
 

src/ipc/ipc-common.c

@@ -214,6 +214,15 @@ void ipc_msg_send(struct ipc_msg *msg, void *data, bool high_priority)
 	    msg->tx_data != data) {
 		ret = memcpy_s(msg->tx_data, msg->tx_size, data, msg->tx_size);
 		assert(!ret);
+		if (!cpu_is_primary(cpu_get_id())) {
+			/* Write back data to memory to maintain coherence between cores.
+			 * The response was prepared on a secondary core but will be sent
+			 * to the host from the primary core.
+			 */
+			dcache_writeback_region((__sparse_force void __sparse_cache *)msg->tx_data,
+						msg->tx_size);
+			msg->is_shared = true;
+		}
 	}
 
 	/*

src/ipc/ipc4/handler.c

@@ -72,9 +72,9 @@ struct ipc4_msg_data {
 static struct ipc4_msg_data msg_data;
 
 /* fw sends a fw ipc message to send the status of the last host ipc message */
-static struct ipc_msg msg_reply = {0, 0, 0, 0, LIST_INIT(msg_reply.list)};
+static struct ipc_msg msg_reply = {0, 0, 0, 0, false, LIST_INIT(msg_reply.list)};
 
-static struct ipc_msg msg_notify = {0, 0, 0, 0, LIST_INIT(msg_notify.list)};
+static struct ipc_msg msg_notify = {0, 0, 0, 0, false, LIST_INIT(msg_notify.list)};
 
 #if CONFIG_LIBRARY
 static inline struct ipc4_message_request *ipc4_get_message_request(void)
@@ -1494,14 +1494,25 @@ struct ipc_cmd_hdr *ipc_prepare_to_send(const struct ipc_msg *msg)
 	msg_data.msg_out.pri = msg->header;
 	msg_data.msg_out.ext = msg->extension;
 
-	if (msg->tx_size)
+	if (msg->tx_size) {
+		/* Invalidate cache to ensure we read the latest data from memory.
+		 * The response was prepared on a secondary core but will be sent
+		 * to the host from the primary core.
+		 */
+		if (msg->is_shared) {
+			dcache_invalidate_region((__sparse_force void __sparse_cache *)msg->tx_data,
+						 msg->tx_size);
+		}
+
 		mailbox_dspbox_write(0, (uint32_t *)msg->tx_data, msg->tx_size);
+	}
 
 	/* free memory for get config function */
 	if (msg == &msg_reply && msg_reply.tx_size > 0) {
 		rfree(msg_reply.tx_data);
 		msg_reply.tx_data = NULL;
 		msg_reply.tx_size = 0;
+		msg_reply.is_shared = false;
 	}
 
 	return &msg_data.msg_out;
@@ -1535,6 +1546,7 @@ void ipc_send_panic_notification(void)
 {
 	msg_notify.header = SOF_IPC4_NOTIF_HEADER(SOF_IPC4_EXCEPTION_CAUGHT);
 	msg_notify.extension = cpu_get_id();
+	msg_notify.is_shared = !cpu_is_primary(cpu_get_id());
 	msg_notify.tx_size = 0;
 	msg_notify.tx_data = NULL;
 	list_init(&msg_notify.list);
@@ -1567,6 +1579,7 @@ void ipc_send_buffer_status_notify(void)
 	msg_notify.header = SOF_IPC4_NOTIF_HEADER(SOF_IPC4_NOTIFY_LOG_BUFFER_STATUS);
 	msg_notify.extension = 0;
 	msg_notify.tx_size = 0;
+	msg_notify.is_shared = false;
 
 	tr_dbg(&ipc_tr, "tx-notify\t: %#x|%#x", msg_notify.header, msg_notify.extension);
 

src/library_manager/lib_notification.c

@@ -73,6 +73,7 @@ struct ipc_msg *lib_notif_msg_init(uint32_t header, uint32_t size)
 	/* Update header and size, since message handle can be reused */
 	msg->header = header;
 	msg->tx_size = size;
+	msg->is_shared = !cpu_is_primary(cpu_get_id());
 	return msg;
 }