[PATCHv2 04/27] crypto: omap-sham: set sw fallback to 240 bytes

[Tero Kristo]

From: Bin Liu <b-liu at ti.com>

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 at ti.com>
[t-kristo at ti.com: dropped the extra traces, updated some comments
 on the code]
Signed-off-by: Tero Kristo <t-kristo at ti.com>
---
 drivers/crypto/omap-sham.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/drivers/crypto/omap-sham.c b/drivers/crypto/omap-sham.c
index fd3cac3..6247887 100644
--- a/drivers/crypto/omap-sham.c
+++ b/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);
-- 
1.9.1