--- /dev/null
+From 2d3b6fae7d1a2ad821769440daa91d7eec5c8250 Mon Sep 17 00:00:00 2001
+From: Eneas U de Queiroz <cotequeiroz@gmail.com>
+Date: Fri, 20 Dec 2019 09:41:44 -0300
+Subject: [PATCH] crypto: qce - use AES fallback for small requests
+
+Process small blocks using the fallback cipher, as a workaround for an
+observed failure (DMA-related, apparently) when computing the GCM ghash
+key. This brings a speed gain as well, since it avoids the latency of
+using the hardware engine to process small blocks.
+
+Using software for all 16-byte requests would be enough to make GCM
+work, but to increase performance, a larger threshold would be better.
+Measuring the performance of supported ciphers with openssl speed,
+software matches hardware at around 768-1024 bytes.
+
+Considering the 256-bit ciphers, software is 2-3 times faster than qce
+at 256-bytes, 30% faster at 512, and about even at 768-bytes. With
+128-bit keys, the break-even point would be around 1024-bytes.
+
+This adds the 'aes_sw_max_len' parameter, to set the largest request
+length processed by the software fallback. Its default is being set to
+512 bytes, a little lower than the break-even point, to balance the cost
+in CPU usage.
+
+Signed-off-by: Eneas U de Queiroz <cotequeiroz@gmail.com>
+
+--- a/drivers/crypto/Kconfig
++++ b/drivers/crypto/Kconfig
+@@ -585,6 +585,29 @@ config CRYPTO_DEV_QCE
+ hardware. To compile this driver as a module, choose M here. The
+ module will be called qcrypto.
+
++config CRYPTO_DEV_QCE_SW_MAX_LEN
++ int "Default maximum request size to use software for AES"
++ depends on CRYPTO_DEV_QCE && CRYPTO_DEV_QCE_SKCIPHER
++ default 512
++ help
++ This sets the default maximum request size to perform AES requests
++ using software instead of the crypto engine. It can be changed by
++ setting the aes_sw_max_len parameter.
++
++ Small blocks are processed faster in software than hardware.
++ Considering the 256-bit ciphers, software is 2-3 times faster than
++ qce at 256-bytes, 30% faster at 512, and about even at 768-bytes.
++ With 128-bit keys, the break-even point would be around 1024-bytes.
++
++ The default is set a little lower, to 512 bytes, to balance the
++ cost in CPU usage. The minimum recommended setting is 16-bytes
++ (1 AES block), since AES-GCM will fail if you set it lower.
++ Setting this to zero will send all requests to the hardware.
++
++ Note that 192-bit keys are not supported by the hardware and are
++ always processed by the software fallback, and all DES requests
++ are done by the hardware.
++
+ config CRYPTO_DEV_QCOM_RNG
+ tristate "Qualcomm Random Number Generator Driver"
+ depends on ARCH_QCOM || COMPILE_TEST
+--- a/drivers/crypto/qce/skcipher.c
++++ b/drivers/crypto/qce/skcipher.c
+@@ -13,6 +13,7 @@
+
+ #include <linux/device.h>
+ #include <linux/interrupt.h>
++#include <linux/moduleparam.h>
+ #include <linux/types.h>
+ #include <crypto/aes.h>
+ #include <crypto/des.h>
+@@ -20,6 +21,13 @@
+
+ #include "cipher.h"
+
++static unsigned int aes_sw_max_len = CONFIG_CRYPTO_DEV_QCE_SW_MAX_LEN;
++module_param(aes_sw_max_len, uint, 0644);
++MODULE_PARM_DESC(aes_sw_max_len,
++ "Only use hardware for AES requests larger than this "
++ "[0=always use hardware; anything <16 breaks AES-GCM; default="
++ __stringify(CONFIG_CRYPTO_DEV_QCE_SOFT_THRESHOLD)"]");
++
+ static LIST_HEAD(skcipher_algs);
+
+ static void qce_skcipher_done(void *data)
+@@ -170,15 +178,7 @@ static int qce_skcipher_setkey(struct cr
+ if (!key || !keylen)
+ return -EINVAL;
+
+- if (IS_AES(flags)) {
+- switch (IS_XTS(flags) ? keylen >> 1 : keylen) {
+- case AES_KEYSIZE_128:
+- case AES_KEYSIZE_256:
+- break;
+- default:
+- goto fallback;
+- }
+- } else if (IS_DES(flags)) {
++ if (IS_DES(flags)) {
+ u32 tmp[DES_EXPKEY_WORDS];
+
+ ret = des_ekey(tmp, key);
+@@ -189,8 +189,8 @@ static int qce_skcipher_setkey(struct cr
+
+ ctx->enc_keylen = keylen;
+ memcpy(ctx->enc_key, key, keylen);
+- return 0;
+-fallback:
++ if (!IS_AES(flags))
++ return 0;
+ ret = crypto_skcipher_setkey(ctx->fallback, key, keylen);
+ if (!ret)
+ ctx->enc_keylen = keylen;
+@@ -213,8 +213,9 @@ static int qce_skcipher_crypt(struct skc
+ rctx->flags |= encrypt ? QCE_ENCRYPT : QCE_DECRYPT;
+ keylen = IS_XTS(rctx->flags) ? ctx->enc_keylen >> 1 : ctx->enc_keylen;
+
+- if (IS_AES(rctx->flags) && keylen != AES_KEYSIZE_128 &&
+- keylen != AES_KEYSIZE_256) {
++ if (IS_AES(rctx->flags) &&
++ ((keylen != AES_KEYSIZE_128 && keylen != AES_KEYSIZE_256) ||
++ req->cryptlen <= aes_sw_max_len)) {
+ SKCIPHER_REQUEST_ON_STACK(subreq, ctx->fallback);
+
+ skcipher_request_set_tfm(subreq, ctx->fallback);
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