crypto: omap-sham - set sw fallback to 240 bytes

Adds software fallback support for small crypto requests. In these cases,
it is undesirable to use DMA, as setting it up itself is rather heavy
operation. Gives about 40% extra performance in ipsec usecase.

Signed-off-by: Bin Liu <b-liu@ti.com>
[t-kristo@ti.com: dropped the extra traces, updated some comments
 on the code]
Signed-off-by: Tero Kristo <t-kristo@ti.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

drivers/crypto/omap-sham.c

@@ -1095,7 +1095,7 @@ static int omap_sham_update(struct ahash_request *req)
 	ctx->offset = 0;
 
 	if (ctx->flags & BIT(FLAGS_FINUP)) {
-		if ((ctx->digcnt + ctx->bufcnt + ctx->total) < 9) {
+		if ((ctx->digcnt + ctx->bufcnt + ctx->total) < 240) {
 			/*
 			* OMAP HW accel works only with buffers >= 9
 			* will switch to bypass in final()
@@ -1151,9 +1151,13 @@ static int omap_sham_final(struct ahash_request *req)
 	if (ctx->flags & BIT(FLAGS_ERROR))
 		return 0; /* uncompleted hash is not needed */
 
-	/* OMAP HW accel works only with buffers >= 9 */
-	/* HMAC is always >= 9 because ipad == block size */
-	if ((ctx->digcnt + ctx->bufcnt) < 9)
+	/*
+	 * OMAP HW accel works only with buffers >= 9.
+	 * HMAC is always >= 9 because ipad == block size.
+	 * If buffersize is less than 240, we use fallback SW encoding,
+	 * as using DMA + HW in this case doesn't provide any benefit.
+	 */
+	if ((ctx->digcnt + ctx->bufcnt) < 240)
 		return omap_sham_final_shash(req);
 	else if (ctx->bufcnt)
 		return omap_sham_enqueue(req, OP_FINAL);