crypto: mxs-dcp - Optimize hashing

Optimize the hashing operation in the MXS-DCP by doing two adjustments:
1) Given that the output buffer for the hash is now always correctly aligned,
we can just use the buffer for the DCP DMA to store the resulting hash.
We thus get rid of one copying of data. Moreover, we remove an entry from
dcp_coherent_block{} and thus lower the memory footprint of the driver.
2) We map the output buffer for the hash for DMA only in case we will output
the hash, not always, as it was now.

Signed-off-by: Marek Vasut <[e-mail]>
Cc: David S. Miller <[e-mail]>
Cc: Fabio Estevam <[e-mail]>
Cc: Herbert Xu <[e-mail]>
Cc: Shawn Guo <[e-mail]>
Cc: Tom Lendacky <[e-mail]>
Signed-off-by: Herbert Xu <[e-mail]>

drivers/crypto/mxs-dcp.c

···
 	uint8_t			sha_in_buf[DCP_BUF_SZ];
 
 	uint8_t			aes_key[2 * AES_KEYSIZE_128];
-	uint8_t			sha_digest[SHA256_DIGEST_SIZE];
 
 	struct dcp_dma_desc	desc[DCP_MAX_CHANS];
 };
···
 	struct crypto_ahash *tfm = crypto_ahash_reqtfm(req);
 	struct dcp_async_ctx *actx = crypto_ahash_ctx(tfm);
 	struct dcp_sha_req_ctx *rctx = ahash_request_ctx(req);
+	struct hash_alg_common *halg = crypto_hash_alg_common(tfm);
 
 	struct dcp_dma_desc *desc = &sdcp->coh->desc[actx->chan];
-	dma_addr_t digest_phys = dma_map_single(sdcp->dev,
-						sdcp->coh->sha_digest,
-						SHA256_DIGEST_SIZE,
-						DMA_FROM_DEVICE);
 
+	dma_addr_t digest_phys = 0;
 	dma_addr_t buf_phys = dma_map_single(sdcp->dev, sdcp->coh->sha_in_buf,
 					     DCP_BUF_SZ, DMA_TO_DEVICE);
 
···
 
 	/* Set HASH_TERM bit for last transfer block. */
 	if (rctx->fini) {
+		digest_phys = dma_map_single(sdcp->dev, req->result,
+					     halg->digestsize, DMA_FROM_DEVICE);
 		desc->control0 |= MXS_DCP_CONTROL0_HASH_TERM;
 		desc->payload = digest_phys;
 	}
 
 	ret = mxs_dcp_start_dma(actx);
 
-	dma_unmap_single(sdcp->dev, digest_phys, SHA256_DIGEST_SIZE,
-			 DMA_FROM_DEVICE);
+	if (rctx->fini)
+		dma_unmap_single(sdcp->dev, digest_phys, halg->digestsize,
+				 DMA_FROM_DEVICE);
+
 	dma_unmap_single(sdcp->dev, buf_phys, DCP_BUF_SZ, DMA_TO_DEVICE);
 
 	return ret;
···
 	struct hash_alg_common *halg = crypto_hash_alg_common(tfm);
 	const int nents = sg_nents(req->src);
 
-	uint8_t *digest = sdcp->coh->sha_digest;
 	uint8_t *in_buf = sdcp->coh->sha_in_buf;
 
 	uint8_t *src_buf;
···
 		rctx->fini = 1;
 
 		/* Submit whatever is left. */
+		if (!req->result)
+			return -EINVAL;
+
 		ret = mxs_dcp_run_sha(req);
-		if (ret || !req->result)
+		if (ret)
 			return ret;
+
 		actx->fill = 0;
 
 		/* For some reason, the result is flipped. */
-		for (i = 0; i < halg->digestsize; i++)
-			req->result[i] = digest[halg->digestsize - i - 1];
+		for (i = 0; i < halg->digestsize / 2; i++) {
+			swap(req->result[i],
+			     req->result[halg->digestsize - i - 1]);
+		}
 	}
 
 	return 0;