crypto: hisilicon/sec - add some comments for soft fallback

Modify the print of information that might lead to user misunderstanding.
Currently only XTS mode need the fallback tfm when using 192bit key.
Others algs not need soft fallback tfm. So others algs can return
directly.
Signed-off-by: Kai Ye <yekai13@huawei.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

drivers/crypto/hisilicon/sec2/sec_crypto.c

@@ -641,13 +641,15 @@ static int sec_skcipher_fbtfm_init(struct crypto_skcipher *tfm)
 	struct sec_cipher_ctx *c_ctx = &ctx->c_ctx;
 
 	c_ctx->fallback = false;
+
+	/* Currently, only XTS mode need fallback tfm when using 192bit key */
 	if (likely(strncmp(alg, "xts", SEC_XTS_NAME_SZ)))
 		return 0;
 
 	c_ctx->fbtfm = crypto_alloc_sync_skcipher(alg, 0,
 						  CRYPTO_ALG_NEED_FALLBACK);
 	if (IS_ERR(c_ctx->fbtfm)) {
-		pr_err("failed to alloc fallback tfm!\n");
+		pr_err("failed to alloc xts mode fallback tfm!\n");
 		return PTR_ERR(c_ctx->fbtfm);
 	}
 
@@ -808,7 +810,7 @@ static int sec_skcipher_setkey(struct crypto_skcipher *tfm, const u8 *key,
 	}
 
 	memcpy(c_ctx->c_key, key, keylen);
-	if (c_ctx->fallback) {
+	if (c_ctx->fallback && c_ctx->fbtfm) {
 		ret = crypto_sync_skcipher_setkey(c_ctx->fbtfm, key, keylen);
 		if (ret) {
 			dev_err(dev, "failed to set fallback skcipher key!\n");
@@ -2032,13 +2034,12 @@ static int sec_skcipher_soft_crypto(struct sec_ctx *ctx,
 				    struct skcipher_request *sreq, bool encrypt)
 {
 	struct sec_cipher_ctx *c_ctx = &ctx->c_ctx;
+	SYNC_SKCIPHER_REQUEST_ON_STACK(subreq, c_ctx->fbtfm);
 	struct device *dev = ctx->dev;
 	int ret;
 
-	SYNC_SKCIPHER_REQUEST_ON_STACK(subreq, c_ctx->fbtfm);
-
 	if (!c_ctx->fbtfm) {
-		dev_err(dev, "failed to check fallback tfm\n");
+		dev_err_ratelimited(dev, "the soft tfm isn't supported in the current system.\n");
 		return -EINVAL;
 	}
 
@@ -2256,7 +2257,6 @@ static int sec_aead_param_check(struct sec_ctx *ctx, struct sec_req *sreq)
 	if (ctx->sec->qm.ver == QM_HW_V2) {
 		if (unlikely(!req->cryptlen || (!sreq->c_req.encrypt &&
 		    req->cryptlen <= authsize))) {
-			dev_err(dev, "Kunpeng920 not support 0 length!\n");
 			ctx->a_ctx.fallback = true;
 			return -EINVAL;
 		}