crypto: picoxcell - fix possible status FIFO overflow

The SPAcc's have 2 equally sized FIFO's - a command FIFO and a status
FIFO.  The command FIFO takes the requests that are to be performed and
the status FIFO reports the results.  It is possible to get into the
situation where there are more free spaces in the command FIFO than the
status FIFO if we don't empty the status FIFO quickly enough resulting
in a possible overflow of the status FIFO.  This can result in incorrect
status being reported in the status FIFO.

Make sure that when we are submitting requests the number of requests
that have been dispatched but not yet popped from the status FIFO does
not exceed the size of a single FIFO.

Signed-off-by: Jamie Iles <jamie@jamieiles.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

drivers/crypto/picoxcell_crypto.c

@@ -176,6 +176,8 @@ struct spacc_aead_ctx {
 	u8				salt[AES_BLOCK_SIZE];
 };
 
+static int spacc_ablk_submit(struct spacc_req *req);
+
 static inline struct spacc_alg *to_spacc_alg(struct crypto_alg *alg)
 {
 	return alg ? container_of(alg, struct spacc_alg, alg) : NULL;
@@ -666,6 +668,24 @@ static int spacc_aead_submit(struct spacc_req *req)
 	return -EINPROGRESS;
 }
 
+static int spacc_req_submit(struct spacc_req *req);
+
+static void spacc_push(struct spacc_engine *engine)
+{
+	struct spacc_req *req;
+
+	while (!list_empty(&engine->pending) &&
+	       engine->in_flight + 1 <= engine->fifo_sz) {
+
+		++engine->in_flight;
+		req = list_first_entry(&engine->pending, struct spacc_req,
+				       list);
+		list_move_tail(&req->list, &engine->in_progress);
+
+		req->result = spacc_req_submit(req);
+	}
+}
+
 /*
  * Setup an AEAD request for processing. This will configure the engine, load
  * the context and then start the packet processing.
@@ -698,17 +718,17 @@ static int spacc_aead_setup(struct aead_request *req, u8 *giv,
 
 	err = -EINPROGRESS;
 	spin_lock_irqsave(&engine->hw_lock, flags);
-	if (unlikely(spacc_fifo_cmd_full(engine))) {
+	if (unlikely(spacc_fifo_cmd_full(engine)) ||
+	    engine->in_flight + 1 > engine->fifo_sz) {
 		if (!(req->base.flags & CRYPTO_TFM_REQ_MAY_BACKLOG)) {
 			err = -EBUSY;
 			spin_unlock_irqrestore(&engine->hw_lock, flags);
 			goto out_free_ddts;
 		}
 		list_add_tail(&dev_req->list, &engine->pending);
 	} else {
-		++engine->in_flight;
-		list_add_tail(&dev_req->list, &engine->in_progress);
-		spacc_aead_submit(dev_req);
+		list_add_tail(&dev_req->list, &engine->pending);
+		spacc_push(engine);
 	}
 	spin_unlock_irqrestore(&engine->hw_lock, flags);
 
@@ -1041,17 +1061,17 @@ static int spacc_ablk_setup(struct ablkcipher_request *req, unsigned alg_type,
 	 * we either stick it on the end of a pending list if we can backlog,
 	 * or bailout with an error if not.
 	 */
-	if (unlikely(spacc_fifo_cmd_full(engine))) {
+	if (unlikely(spacc_fifo_cmd_full(engine)) ||
+	    engine->in_flight + 1 > engine->fifo_sz) {
 		if (!(req->base.flags & CRYPTO_TFM_REQ_MAY_BACKLOG)) {
 			err = -EBUSY;
 			spin_unlock_irqrestore(&engine->hw_lock, flags);
 			goto out_free_ddts;
 		}
 		list_add_tail(&dev_req->list, &engine->pending);
 	} else {
-		++engine->in_flight;
-		list_add_tail(&dev_req->list, &engine->in_progress);
-		spacc_ablk_submit(dev_req);
+		list_add_tail(&dev_req->list, &engine->pending);
+		spacc_push(engine);
 	}
 	spin_unlock_irqrestore(&engine->hw_lock, flags);
 
@@ -1139,6 +1159,7 @@ static void spacc_process_done(struct spacc_engine *engine)
 		req = list_first_entry(&engine->in_progress, struct spacc_req,
 				       list);
 		list_move_tail(&req->list, &engine->completed);
+		--engine->in_flight;
 
 		/* POP the status register. */
 		writel(~0, engine->regs + SPA_STAT_POP_REG_OFFSET);
@@ -1208,36 +1229,21 @@ static void spacc_spacc_complete(unsigned long data)
 	struct spacc_engine *engine = (struct spacc_engine *)data;
 	struct spacc_req *req, *tmp;
 	unsigned long flags;
-	int num_removed = 0;
 	LIST_HEAD(completed);
 
 	spin_lock_irqsave(&engine->hw_lock, flags);
+
 	list_splice_init(&engine->completed, &completed);
+	spacc_push(engine);
+	if (engine->in_flight)
+		mod_timer(&engine->packet_timeout, jiffies + PACKET_TIMEOUT);
+
 	spin_unlock_irqrestore(&engine->hw_lock, flags);
 
 	list_for_each_entry_safe(req, tmp, &completed, list) {
-		++num_removed;
 		req->complete(req);
+		list_del(&req->list);
 	}
-
-	/* Try and fill the engine back up again. */
-	spin_lock_irqsave(&engine->hw_lock, flags);
-
-	engine->in_flight -= num_removed;
-
-	list_for_each_entry_safe(req, tmp, &engine->pending, list) {
-		if (spacc_fifo_cmd_full(engine))
-			break;
-
-		list_move_tail(&req->list, &engine->in_progress);
-		++engine->in_flight;
-		req->result = spacc_req_submit(req);
-	}
-
-	if (engine->in_flight)
-		mod_timer(&engine->packet_timeout, jiffies + PACKET_TIMEOUT);
-
-	spin_unlock_irqrestore(&engine->hw_lock, flags);
 }
 
 #ifdef CONFIG_PM