crypto: inside-secure - Fix hang case on EIP97 with zero length input data

The EIP97 hardware cannot handle zero length input data and will (usually)
hang when presented with this anyway. This patch converts any zero length
input to a 1 byte dummy input to prevent this hanging.
Signed-off-by: Pascal van Leeuwen <pvanleeuwen@rambus.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

drivers/crypto/inside-secure/safexcel_cipher.c

@@ -782,16 +782,31 @@ static int safexcel_send_req(struct crypto_async_request *base, int ring,
 
 	memcpy(ctx->base.ctxr->data, ctx->key, ctx->key_len);
 
-	/* The EIP cannot deal with zero length input packets! */
-	if (totlen == 0)
-		totlen = 1;
+	if (!totlen) {
+		/*
+		 * The EIP97 cannot deal with zero length input packets!
+		 * So stuff a dummy command descriptor indicating a 1 byte
+		 * (dummy) input packet, using the context record as source.
+		 */
+		first_cdesc = safexcel_add_cdesc(priv, ring,
+						 1, 1, ctx->base.ctxr_dma,
+						 1, 1, ctx->base.ctxr_dma,
+						 &atoken);
+		if (IS_ERR(first_cdesc)) {
+			/* No space left in the command descriptor ring */
+			ret = PTR_ERR(first_cdesc);
+			goto cdesc_rollback;
+		}
+		n_cdesc = 1;
+		goto skip_cdesc;
+	}
 
 	/* command descriptors */
 	for_each_sg(src, sg, sreq->nr_src, i) {
 		int len = sg_dma_len(sg);
 
 		/* Do not overflow the request */
-		if (queued - len < 0)
+		if (queued < len)
 			len = queued;
 
 		cdesc = safexcel_add_cdesc(priv, ring, !n_cdesc,
@@ -803,27 +818,16 @@ static int safexcel_send_req(struct crypto_async_request *base, int ring,
 			ret = PTR_ERR(cdesc);
 			goto cdesc_rollback;
 		}
-		n_cdesc++;
 
-		if (n_cdesc == 1) {
+		if (!n_cdesc)
 			first_cdesc = cdesc;
-		}
 
+		n_cdesc++;
 		queued -= len;
 		if (!queued)
 			break;
 	}
-
-	if (unlikely(!n_cdesc)) {
-		/*
-		 * Special case: zero length input buffer.
-		 * The engine always needs the 1st command descriptor, however!
-		 */
-		first_cdesc = safexcel_add_cdesc(priv, ring, 1, 1, 0, 0, totlen,
-						 ctx->base.ctxr_dma, &atoken);
-		n_cdesc = 1;
-	}
-
+skip_cdesc:
 	/* Add context control words and token to first command descriptor */
 	safexcel_context_control(ctx, base, sreq, first_cdesc);
 	if (ctx->aead)