crypto: omap-aes-gcm - fix corner case with only auth data

Fix a corner case where only authdata is generated, without any provided
assocdata / cryptdata. Passing the empty scatterlists to OMAP AES core driver
in this case would confuse it, failing to map DMAs.
Signed-off-by: Tero Kristo <t-kristo@ti.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

drivers/crypto/omap-aes-gcm.c

@@ -148,12 +148,14 @@ static int omap_aes_gcm_copy_buffers(struct omap_aes_dev *dd,
 	if (req->src == req->dst || dd->out_sg == sg_arr)
 		flags |= OMAP_CRYPTO_FORCE_COPY;
 
+	if (cryptlen) {
 		ret = omap_crypto_align_sg(&dd->out_sg, cryptlen,
 					   AES_BLOCK_SIZE, &dd->out_sgl,
 					   flags,
 					   FLAGS_OUT_DATA_ST_SHIFT, &dd->flags);
 		if (ret)
 			return ret;
+	}
 
 	dd->in_sg_len = sg_nents_for_len(dd->in_sg, alen + clen);
 	dd->out_sg_len = sg_nents_for_len(dd->out_sg, clen);
@@ -287,8 +289,12 @@ static int omap_aes_gcm_handle_queue(struct omap_aes_dev *dd,
 		return err;
 
 	err = omap_aes_write_ctrl(dd);
-	if (!err)
+	if (!err) {
+		if (dd->in_sg_len && dd->out_sg_len)
 			err = omap_aes_crypt_dma_start(dd);
+		else
+			omap_aes_gcm_dma_out_callback(dd);
+	}
 
 	if (err) {
 		omap_aes_gcm_finish_req(dd, err);