ipc4: Add notification pool

Add a pool of IPC messages for sending notifications. These messages are
dynamically allocated as needed. Add a callback to the ipc_msg structure
that is called after sending a message, allowing messages to be returned
to the pool once sent.

Using a notification pool simplifies the process of sending sporadic
notifications by components. This approach eliminates the need for
components to manage the allocation and release of notifications.
Additionally, it conserves memory, as notifications that are never sent
during normal operation will not be allocated.

Signed-off-by: Adrian Warecki <adrian.warecki@intel.com>

Author: softwarecki

src/include/sof/ipc/msg.h

@@ -36,6 +36,7 @@ struct ipc_msg {
 	uint32_t tx_size;	/* payload size in bytes */
 	void *tx_data;		/* pointer to payload data, must be in a non-cached memory */
 	struct list_item list;
+	void (*callback)(struct ipc_msg *msg); /* Function called after sending the message */
 };
 
 /**

src/include/sof/ipc/notification_pool.h

@@ -0,0 +1,26 @@
+/* SPDX-License-Identifier: BSD-3-Clause
+ *
+ * Copyright(c) 2025 Intel Corporation. All rights reserved.
+ *
+ * Author: Adrian Warecki <adrian.warecki@intel.com>
+ */
+
+#ifndef __SOF_IPC_NOTIFICATION_POOL_H__
+#define __SOF_IPC_NOTIFICATION_POOL_H__
+
+#include <stdint.h>
+#include <sof/ipc/msg.h>
+
+/**
+ * @brief Retrieves an IPC notification message from the pool.
+ *
+ * This function retrieves and returns an IPC notification message
+ * of the specified size from the notification pool. The size of the
+ * message is limited by the maximum size available in the pool.
+ *
+ * @param size The size of the IPC message to retrieve.
+ * @return A pointer to the retrieved IPC message, or NULL if retrieval fails.
+ */
+struct ipc_msg *ipc_notification_pool_get(size_t size);
+
+#endif /* __SOF_IPC_NOTIFICATION_POOL_H__ */

src/ipc/CMakeLists.txt

@@ -10,6 +10,7 @@ endif()
 add_local_sources(sof
 	ipc-common.c
 	ipc-helper.c
+	notification_pool.c
 )
 
 is_zephyr(it_is)

src/ipc/ipc-common.c

@@ -162,6 +162,9 @@ void ipc_send_queued_msg(void)
 	if (ipc_platform_send_msg(msg) == 0) {
 		/* Remove the message from the list if it has been successfully sent. */
 		list_item_del(&msg->list);
+		/* Invoke a callback to notify that the message has been sent. */
+		if (msg->callback)
+			msg->callback(msg);
 #ifdef CONFIG_SOF_TELEMETRY_IO_PERFORMANCE_MEASUREMENTS
 		/* Increment performance counters */
 		io_perf_monitor_update_data(ipc->io_perf_out_msg_count, 1);

src/ipc/notification_pool.c

@@ -0,0 +1,100 @@
+// SPDX-License-Identifier: BSD-3-Clause
+//
+// Copyright(c) 2025 Intel Corporation. All rights reserved.
+//
+// Author: Adrian Warecki <adrian.warecki@intel.com>
+//
+
+#include <stdint.h>
+#include <sof/common.h>
+#include <sof/list.h>
+#include <sof/ipc/notification_pool.h>
+
+#define NOTIFICATION_POOL_MAX_PAYLOAD_SIZE	40	/* IPC4 Resource Event needs 10dw */
+#define NOTIFICATION_POOL_MAX_DEPTH		8	/* Maximum number of notifications
+							 * in the pool
+							 */
+
+LOG_MODULE_REGISTER(notification_pool, CONFIG_SOF_LOG_LEVEL);
+
+SOF_DEFINE_REG_UUID(notification_pool);
+
+DECLARE_TR_CTX(notif_tr, SOF_UUID(notification_pool_uuid), LOG_LEVEL_INFO);
+
+struct ipc_notif_pool_item {
+	struct ipc_msg msg;
+	uint32_t payload[SOF_DIV_ROUND_UP(NOTIFICATION_POOL_MAX_PAYLOAD_SIZE, sizeof(uint32_t))];
+};
+
+static struct list_item pool_free_list = LIST_INIT(pool_free_list);
+static struct k_spinlock pool_free_list_lock;
+static int pool_depth;
+
+static void ipc_notif_free(struct ipc_msg *msg)
+{
+	struct ipc_notif_pool_item *item = container_of(msg, struct ipc_notif_pool_item, msg);
+	k_spinlock_key_t key;
+
+	key = k_spin_lock(&pool_free_list_lock);
+	list_item_append(&item->msg.list, &pool_free_list);
+	k_spin_unlock(&pool_free_list_lock, key);
+}
+
+static struct ipc_msg *ipc_notif_new(size_t size)
+{
+	struct ipc_notif_pool_item *item;
+
+	item = rzalloc(SOF_MEM_ZONE_RUNTIME_SHARED, 0, SOF_MEM_CAPS_RAM, sizeof(*item));
+	if (!item) {
+		tr_err(&notif_tr, "Unable to allocate memory for notification message");
+		return NULL;
+	}
+
+	list_init(&item->msg.list);
+	item->msg.tx_data = item->payload;
+	item->msg.tx_size = size;
+	item->msg.callback = ipc_notif_free;
+	return &item->msg;
+}
+
+struct ipc_msg *ipc_notification_pool_get(size_t size)
+{
+	struct ipc_notif_pool_item *item;
+	k_spinlock_key_t key;
+	struct ipc_msg *new_msg;
+
+	if (size > NOTIFICATION_POOL_MAX_PAYLOAD_SIZE) {
+		tr_err(&notif_tr, "Requested size %zu exceeds maximum payload size %u",
+		       size, NOTIFICATION_POOL_MAX_PAYLOAD_SIZE);
+		return NULL;
+	}
+
+	/* check if we have a free message */
+	key = k_spin_lock(&pool_free_list_lock);
+	if (list_is_empty(&pool_free_list)) {
+		/* allocate a new message */
+		if (pool_depth >= NOTIFICATION_POOL_MAX_DEPTH) {
+			k_spin_unlock(&pool_free_list_lock, key);
+			tr_err(&notif_tr, "Pool depth exceeded");
+			return NULL;
+		}
+		++pool_depth;
+		k_spin_unlock(&pool_free_list_lock, key);
+
+		new_msg = ipc_notif_new(size);
+		if (!new_msg) {
+			key = k_spin_lock(&pool_free_list_lock);
+			--pool_depth;
+			k_spin_unlock(&pool_free_list_lock, key);
+		}
+		return new_msg;
+	}
+
+	/* take the first free message */
+	item = list_first_item(&pool_free_list, struct ipc_notif_pool_item, msg.list);
+	list_item_del(&item->msg.list);
+	k_spin_unlock(&pool_free_list_lock, key);
+
+	item->msg.tx_size = size;
+	return &item->msg;
+}

uuid-registry.txt

@@ -172,3 +172,4 @@ d944281a-afe9-4695-a043d7f62b89538e waves
 2B79E4F3-4675-F649-89DF3BC194A91AEB brngup
 D406D134-C3C1-402C-8AEC6821C0C2B0E6 cold
 c51dc642-a2e1-48df-a490e2748cb6363e tflmcly
+f36BF24B-9AAF-83f4-8677E072E8AEADB7 notification_pool