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>

diff --git a/drivers/net/usb/usbnet.c b/drivers/net/usb/usbnet.c
index 06ee82f557d45ba31b4847c187f57771ae2c73d2..27a00b00603325c61a96d36a7b7ecd1fe64dd269 100644 (file)
--- 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 f18d64129f99982f966f3c2fe733cd85260dc625..2b47e6364e3697ff1fbd684b923da5cd6ec65e82 100644 (file)
--- 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;