Enabling SG allows enabling GSO (generic segmentation offload) feature
of linux networking layer. This increases TCP throughput with NCM
on Cortex-A15+USB3380 based device from 300 Mbit/s to 1.1 Gbit/s.
Signed-off-by: Jussi Kivilinna <jussi.kivili...@haltian.com>
---
drivers/usb/gadget/Kconfig | 2 ++
drivers/usb/gadget/function/f_ncm.c | 47 +++++++++++++++++++++++++++++++------
2 files changed, 42 insertions(+), 7 deletions(-)
diff --git a/drivers/usb/gadget/Kconfig b/drivers/usb/gadget/Kconfig
index 3c3f31c..3a8b874 100644
--- a/drivers/usb/gadget/Kconfig
+++ b/drivers/usb/gadget/Kconfig
@@ -277,6 +277,8 @@ config USB_CONFIGFS_NCM
depends on NET
select USB_U_ETHER
select USB_F_NCM
+ select CRYPTO
+ select CRYPTO_CRC32
help
NCM is an advanced protocol for Ethernet encapsulation, allows
grouping of several ethernet frames into one USB transfer and
diff --git a/drivers/usb/gadget/function/f_ncm.c
b/drivers/usb/gadget/function/f_ncm.c
index 08cff49..1f4f724 100644
--- a/drivers/usb/gadget/function/f_ncm.c
+++ b/drivers/usb/gadget/function/f_ncm.c
@@ -20,6 +20,8 @@
#include <linux/device.h>
#include <linux/etherdevice.h>
#include <linux/crc32.h>
+#include <crypto/hash.h>
+#include <linux/scatterlist.h>
#include <linux/usb/cdc.h>
@@ -80,6 +82,10 @@ struct f_ncm {
struct hrtimer task_timer;
bool timer_stopping;
+
+ /* For scatter/gather crc32 */
+ struct crypto_ahash *tfm;
+ struct scatterlist sg[MAX_SKB_FRAGS + 1];
};
static inline struct f_ncm *func_to_ncm(struct usb_function *f)
@@ -1017,6 +1023,25 @@ static struct sk_buff *package_for_tx(struct f_ncm *ncm)
return skb2;
}
+static u32 skb_crc(struct f_ncm *ncm, struct sk_buff *skb)
+{
+ AHASH_REQUEST_ON_STACK(req, ncm->tfm);
+ __le32 crc = cpu_to_le32(~(u32)0);
+
+ sg_init_table(ncm->sg, MAX_SKB_FRAGS + 1);
+ skb_to_sgvec(skb, ncm->sg, 0, skb->len);
+
+ crypto_ahash_setkey(ncm->tfm, (void *)&crc, sizeof(crc));
+
+ ahash_request_set_tfm(req, ncm->tfm);
+ ahash_request_set_callback(req, 0, NULL, NULL);
+ ahash_request_set_crypt(req, ncm->sg, (void *)&crc, skb->len);
+
+ crypto_ahash_digest(req);
+
+ return ~le32_to_cpu(crc);
+}
+
static struct sk_buff *ncm_wrap_ntb(struct gether *port,
struct sk_buff *skb)
{
@@ -1040,13 +1065,11 @@ static struct sk_buff *ncm_wrap_ntb(struct gether *port,
if (skb) {
/* Add the CRC if required up front */
if (ncm->is_crc) {
- uint32_t crc;
- __le16 *crc_pos;
+ u32 crc;
+ __le32 *crc_pos;
- crc = ~crc32_le(~0,
- skb->data,
- skb->len);
- crc_pos = (void *) skb_put(skb, sizeof(uint32_t));
+ crc = skb_crc(ncm, skb);
+ crc_pos = (void *) skb_put(skb, sizeof(u32));
put_unaligned_le32(crc, crc_pos);
}
@@ -1130,7 +1153,7 @@ static struct sk_buff *ncm_wrap_ntb(struct gether *port,
ntb_data = (void *) skb_put(ncm->skb_tx_data, dgram_pad);
memset(ntb_data, 0, dgram_pad);
ntb_data = (void *) skb_put(ncm->skb_tx_data, skb->len);
- memcpy(ntb_data, skb->data, skb->len);
+ skb_copy_bits(skb, 0, ntb_data, skb->len);
dev_kfree_skb_any(skb);
skb = NULL;
@@ -1513,6 +1536,12 @@ static int ncm_bind(struct usb_configuration *c, struct
usb_function *f)
if (status)
goto fail;
+ ncm->tfm = crypto_alloc_ahash("crc32", 0, CRYPTO_ALG_ASYNC);
+ if (IS_ERR(ncm->tfm)) {
+ usb_free_all_descriptors(f);
+ goto fail;
+ }
+
/*
* NOTE: all that is done without knowing or caring about
* the network link ... which is unavailable to this code
@@ -1607,6 +1636,8 @@ static struct usb_function_instance *ncm_alloc_inst(void)
return ERR_CAST(net);
}
+ opts->net->features |= NETIF_F_SG;
+
config_group_init_type_name(&opts->func_inst.group, "", &ncm_func_type);
return &opts->func_inst;
@@ -1634,6 +1665,8 @@ static void ncm_unbind(struct usb_configuration *c,
struct usb_function *f)
hrtimer_cancel(&ncm->task_timer);
tasklet_kill(&ncm->tx_tasklet);
+ crypto_free_ahash(ncm->tfm);
+
ncm_string_defs[0].id = 0;
usb_free_all_descriptors(f);
--
2.7.4
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