netdev - [PATCH 4/4] USBNET: ax88179_178a: enable tso if host supports sg dma

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Date:	Wed, 31 Jul 2013 18:51:49 +0800
From:	Ming Lei <ming.lei@...onical.com>
To:	"David S. Miller" <davem@...emloft.net>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:	Oliver Neukum <oneukum@...e.de>, Freddy Xin <freddy@...x.com.tw>,
	Eric Dumazet <eric.dumazet@...il.com>,
	Ben Hutchings <bhutchings@...arflare.com>,
	Grant Grundler <grundler@...gle.com>, netdev@...r.kernel.org,
	linux-usb@...r.kernel.org, Ming Lei <ming.lei@...onical.com>
Subject: [PATCH 4/4] USBNET: ax88179_178a: enable tso if host supports sg dma

This patch enables 'can_dma_sg' flag for ax88179_178a device
if the attached host controller supports building packet from
discontinuous buffers(DMA SG is possible), so both frame header
and skb data buffers can be passed to usb stack via urb->sg,
then skb data copy can be saved.

With the patch, CPU utilization decreased much in iperf test at
client mode.

Signed-off-by: Ming Lei <ming.lei@...onical.com>
---
 drivers/net/usb/ax88179_178a.c |   30 ++++++++++++++++++++++++++++++
 1 file changed, 30 insertions(+)

diff --git a/drivers/net/usb/ax88179_178a.c b/drivers/net/usb/ax88179_178a.c
index 5a468f3..c75bded 100644
--- a/drivers/net/usb/ax88179_178a.c
+++ b/drivers/net/usb/ax88179_178a.c
@@ -1031,12 +1031,20 @@ static int ax88179_bind(struct usbnet *dev, struct usb_interface *intf)
 	dev->mii.phy_id = 0x03;
 	dev->mii.supports_gmii = 1;
 
+	if (dev->udev->bus->no_sg_limit)
+		dev->can_dma_sg = 1;
+
 	dev->net->features |= NETIF_F_IP_CSUM | NETIF_F_IPV6_CSUM |
 			      NETIF_F_RXCSUM;
 
 	dev->net->hw_features |= NETIF_F_IP_CSUM | NETIF_F_IPV6_CSUM |
 				 NETIF_F_RXCSUM;
 
+	if (dev->can_dma_sg) {
+		dev->net->features |= NETIF_F_SG | NETIF_F_TSO;
+		dev->net->hw_features |= NETIF_F_SG | NETIF_F_TSO;
+	}
+
 	/* Enable checksum offload */
 	*tmp = AX_RXCOE_IP | AX_RXCOE_TCP | AX_RXCOE_UDP |
 	       AX_RXCOE_TCPV6 | AX_RXCOE_UDPV6;
@@ -1170,12 +1178,30 @@ ax88179_tx_fixup(struct usbnet *dev, struct sk_buff *skb, gfp_t flags)
 	int mss = skb_shinfo(skb)->gso_size;
 	int headroom;
 	int tailroom;
+	struct skb_data *entry = (struct skb_data *)skb->cb;
 
 	tx_hdr1 = skb->len;
 	tx_hdr2 = mss;
 	if (((skb->len + 8) % frame_size) == 0)
 		tx_hdr2 |= 0x80008000;	/* Enable padding */
 
+	if (dev->can_dma_sg) {
+		if (!(entry->header = kmalloc(8, GFP_ATOMIC)))
+			goto no_sg;
+
+		entry->length = 8;
+		cpu_to_le32s(&tx_hdr1);
+		cpu_to_le32s(&tx_hdr2);
+		memcpy(entry->header, &tx_hdr1, 4);
+		memcpy(entry->header + 4, &tx_hdr2, 4);
+
+		return skb;
+	} else {
+no_sg:
+		entry->header = NULL;
+		entry->length = 0;
+	}
+
 	headroom = skb_headroom(skb);
 	tailroom = skb_tailroom(skb);
 
@@ -1323,6 +1349,10 @@ static int ax88179_reset(struct usbnet *dev)
 
 	dev->net->hw_features |= NETIF_F_IP_CSUM | NETIF_F_IPV6_CSUM |
 				 NETIF_F_RXCSUM;
+	if (dev->can_dma_sg) {
+		dev->net->features |= NETIF_F_SG | NETIF_F_TSO;
+		dev->net->hw_features |= NETIF_F_SG | NETIF_F_TSO;
+	}
 
 	/* Enable checksum offload */
 	*tmp = AX_RXCOE_IP | AX_RXCOE_TCP | AX_RXCOE_UDP |
-- 
1.7.9.5

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