[feature] add function to release a scratch tile

When a user doesn't need a tile to be pushed back into the scratchpad,
it is better to just `release` that tile instead. This is particularly
useful for read-only data for applications that are bandwidth limited.

src/aml.h

@@ -1395,6 +1395,7 @@ struct aml_scratch_ops {
 	int (*wait_request)(struct aml_scratch_data *scratch,
 			    struct aml_scratch_request *req);
 	void *(*baseptr)(const struct aml_scratch_data *scratch);
+	int (*release)(struct aml_scratch_data *scratch, int scratchid);
 };
 
 struct aml_scratch {
@@ -1461,6 +1462,7 @@ int aml_scratch_async_push(struct aml_scratch *scratch,
  */
 int aml_scratch_wait(struct aml_scratch *scratch,
 		     struct aml_scratch_request *req);
+
 /*
  * Tears down an asynchronous scratch request before it completes.
  * "scratch": an initialized scratch structure.
@@ -1476,6 +1478,14 @@ int aml_scratch_cancel(struct aml_scratch *scratch,
  */
 void* aml_scratch_baseptr(const struct aml_scratch *scratch);
 
+/*
+ * Release a scratch tile for immediate reuse.
+ * "scratch": an initialized scratchpad structure.
+ * "scratchid": an argument of type int; the scratchpad tile identifier.
+ * Returns 0 if successuf; an error code otherwise.
+ */
+int aml_scratch_release(struct aml_scratch *scratch, int scratchid);
+
 /*******************************************************************************
  * Sequential scratchpad API:
  * Scratchpad uses calling thread to trigger asynchronous dma movements.

src/scratch.c

@@ -85,3 +85,9 @@ void *aml_scratch_baseptr(const struct aml_scratch *scratch)
 	assert(scratch != NULL);
 	return scratch->ops->baseptr(scratch->data);
 }
+
+int aml_scratch_release(struct aml_scratch *scratch, int scratchid)
+{
+	assert(scratch != NULL);
+	return scratch->ops->release(scratch->data, scratchid);
+}

src/scratch_par.c

@@ -191,11 +191,26 @@ void *aml_scratch_par_baseptr(const struct aml_scratch_data *d)
 	return scratch->data.sch_ptr;
 }
 
+int aml_scratch_par_release(struct aml_scratch_data *d, int scratchid)
+{
+	assert(d != NULL);
+	struct aml_scratch_par *scratch = (struct aml_scratch_par *)d;
+	int *tile;
+
+	pthread_mutex_lock(&scratch->data.lock);
+	tile = aml_vector_get(&scratch->data.tilemap, scratchid);
+	if(tile != NULL)
+		aml_vector_remove(&scratch->data.tilemap, tile);
+	pthread_mutex_unlock(&scratch->data.lock);
+	return 0;
+}
+
 struct aml_scratch_ops aml_scratch_par_ops = {
 	aml_scratch_par_create_request,
 	aml_scratch_par_destroy_request,
 	aml_scratch_par_wait_request,
 	aml_scratch_par_baseptr,
+	aml_scratch_par_release,
 };
 
 /*******************************************************************************

src/scratch_seq.c

@@ -193,11 +193,26 @@ void *aml_scratch_seq_baseptr(const struct aml_scratch_data *d)
 	return scratch->data.sch_ptr;
 }
 
+int aml_scratch_seq_release(struct aml_scratch_data *d, int scratchid)
+{
+	assert(d != NULL);
+	struct aml_scratch_seq *scratch = (struct aml_scratch_seq *)d;
+	int *tile;
+
+	pthread_mutex_lock(&scratch->data.lock);
+	tile = aml_vector_get(&scratch->data.tilemap, scratchid);
+	if(tile != NULL)
+		aml_vector_remove(&scratch->data.tilemap, tile);
+	pthread_mutex_unlock(&scratch->data.lock);
+	return 0;
+}
+
 struct aml_scratch_ops aml_scratch_seq_ops = {
 	aml_scratch_seq_create_request,
 	aml_scratch_seq_destroy_request,
 	aml_scratch_seq_wait_request,
 	aml_scratch_seq_baseptr,
+	aml_scratch_seq_release,
 };
 
 /*******************************************************************************