From 638c5115a794981441246fa8fa5d95c1875af5ba Mon Sep 17 00:00:00 2001
From: Ming Lei <ming.lei@canonical.com>
Date: Thu, 8 Aug 2013 21:48:24 +0800
Subject: [PATCH] USBNET: support DMA SG
This patch introduces support of DMA SG if the USB host controller
which usbnet device is attached to is capable of building packet from
discontinuous buffers.
The patch supports passing the skb fragment buffers to usb stack directly
via urb->sg.
Cc: Ben Hutchings <bhutchings@solarflare.com>
Cc: Grant Grundler <grundler@google.com>
Cc: Freddy Xin <freddy@asix.com.tw>
Cc: Alan Stern <stern@rowland.harvard.edu>
Acked-by: Oliver Neukum <oneukum@suse.de>
Signed-off-by: Ming Lei <ming.lei@canonical.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Acked-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/net/usb/usbnet.c | 45 +++++++++++++++++++++++++++++++++++---
include/linux/usb/usbnet.h | 1 +
2 files changed, 43 insertions(+), 3 deletions(-)
diff --git a/drivers/net/usb/usbnet.c b/drivers/net/usb/usbnet.c
index 06ee82f557d45b..27a00b00603325 100644
--- a/drivers/net/usb/usbnet.c
+++ b/drivers/net/usb/usbnet.c
@@ -1197,6 +1197,37 @@ EXPORT_SYMBOL_GPL(usbnet_tx_timeout);
/*-------------------------------------------------------------------------*/
+static int build_dma_sg(const struct sk_buff *skb, struct urb *urb)
+{
+ unsigned num_sgs, total_len = 0;
+ int i, s = 0;
+
+ num_sgs = skb_shinfo(skb)->nr_frags + 1;
+ if (num_sgs == 1)
+ return 0;
+
+ urb->sg = kmalloc(num_sgs * sizeof(struct scatterlist), GFP_ATOMIC);
+ if (!urb->sg)
+ return -ENOMEM;
+
+ urb->num_sgs = num_sgs;
+ sg_init_table(urb->sg, urb->num_sgs);
+
+ sg_set_buf(&urb->sg[s++], skb->data, skb_headlen(skb));
+ total_len += skb_headlen(skb);
+
+ for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {
+ struct skb_frag_struct *f = &skb_shinfo(skb)->frags[i];
+
+ total_len += skb_frag_size(f);
+ sg_set_page(&urb->sg[i + s], f->page.p, f->size,
+ f->page_offset);
+ }
+ urb->transfer_buffer_length = total_len;
+
+ return 1;
+}
+
netdev_tx_t usbnet_start_xmit (struct sk_buff *skb,
struct net_device *net)
{
@@ -1223,7 +1254,6 @@ netdev_tx_t usbnet_start_xmit (struct sk_buff *skb,
goto drop;
}
}
- length = skb->len;
if (!(urb = usb_alloc_urb (0, GFP_ATOMIC))) {
netif_dbg(dev, tx_err, dev->net, "no urb\n");
@@ -1233,10 +1263,14 @@ netdev_tx_t usbnet_start_xmit (struct sk_buff *skb,
entry = (struct skb_data *) skb->cb;
entry->urb = urb;
entry->dev = dev;
- entry->length = length;
usb_fill_bulk_urb (urb, dev->udev, dev->out,
skb->data, skb->len, tx_complete, skb);
+ if (dev->can_dma_sg) {
+ if (build_dma_sg(skb, urb) < 0)
+ goto drop;
+ }
+ entry->length = length = urb->transfer_buffer_length;
/* don't assume the hardware handles USB_ZERO_PACKET
* NOTE: strictly conforming cdc-ether devices should expect
@@ -1305,7 +1339,10 @@ drop:
not_drop:
if (skb)
dev_kfree_skb_any (skb);
- usb_free_urb (urb);
+ if (urb) {
+ kfree(urb->sg);
+ usb_free_urb(urb);
+ }
} else
netif_dbg(dev, tx_queued, dev->net,
"> tx, len %d, type 0x%x\n", length, skb->protocol);
@@ -1356,6 +1393,7 @@ static void usbnet_bh (unsigned long param)
rx_process (dev, skb);
continue;
case tx_done:
+ kfree(entry->urb->sg);
case rx_cleanup:
usb_free_urb (entry->urb);
dev_kfree_skb (skb);
@@ -1689,6 +1727,7 @@ int usbnet_resume (struct usb_interface *intf)
retval = usb_submit_urb(res, GFP_ATOMIC);
if (retval < 0) {
dev_kfree_skb_any(skb);
+ kfree(res->sg);
usb_free_urb(res);
usb_autopm_put_interface_async(dev->intf);
} else {
diff --git a/include/linux/usb/usbnet.h b/include/linux/usb/usbnet.h
index f18d64129f9998..2b47e6364e3697 100644
--- a/include/linux/usb/usbnet.h
+++ b/include/linux/usb/usbnet.h
@@ -34,6 +34,7 @@ struct usbnet {
struct mutex phy_mutex;
unsigned char suspend_count;
unsigned char pkt_cnt, pkt_err;
+ unsigned can_dma_sg:1;
/* i/o info: pipes etc */
unsigned in, out;
--
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