Revert "usb: gadget: u_ether: move hardware transmit to RX NAPI"

This reverts commit 716fb91dfe1777bd6d5e598f3d3572214b3ed296.

That commit caused a regression which would end up in a kernel
BUG() as below:

[  101.554300] g_ether gadget: full-speed config #1: CDC Subset/SAFE
[  101.585186] ------------[ cut here ]------------
[  101.600587] kernel BUG at include/linux/netdevice.h:495!
[  101.615850] Internal error: Oops - BUG: 0 [#1] PREEMPT ARM
[  101.645539] Modules linked in:
[  101.660483] CPU: 0 PID: 0 Comm: swapper Not tainted 3.15.0-rc1+ #104
[  101.690175] task: c05dc5c8 ti: c05d2000 task.ti: c05d2000
[  101.705579] PC is at eth_start+0x64/0x8c
[  101.720981] LR is at __netif_schedule+0x7c/0x90
[  101.736455] pc : [<c0299174>]    lr : [<c036a134>]    psr: 60000093
[  101.736455] sp : c05d3d18  ip : c05d3cf8  fp : c05d3d2c
[  101.782340] r10: 00000000  r9 : c196c1f0  r8 : c196c1a0
[  101.797823] r7 : 00000000  r6 : 00000002  r5 : c1976400  r4 : c1976400
[  101.828058] r3 : 00000000  r2 : c05d3ce8  r1 : 00000001  r0 : 00000002
[  101.858722] Flags: nZCv  IRQs off  FIQs on  Mode SVC_32  ISA ARM Segment kernel

Reported-by: Robert Jarzmik <robert.jarzmik@free.fr>
Signed-of-by: Felipe Balbi <balbi@ti.com>

1 files changed, 35 insertions, 66 deletions

diff --git a/drivers/usb/gadget/u_ether.c b/drivers/usb/gadget/u_ether.c
index 50d09c289137..b7d4f82872b7 100644
--- a/drivers/usb/gadget/u_ether.c
+++ b/drivers/usb/gadget/u_ether.c
@@ -48,8 +48,6 @@
 
 #define UETH__VERSION   "29-May-2008"
 
-#define GETHER_NAPI_WEIGHT      32
-
 struct eth_dev {
         /* lock is held while accessing port_usb
          */
@@ -74,7 +72,6 @@ struct eth_dev {
                                                 struct sk_buff_head *list);
 
         struct work_struct      work;
-        struct napi_struct      rx_napi;
 
         unsigned long           todo;
 #define WORK_RX_MEMORY          0
@@ -256,16 +253,18 @@ enomem:
                 DBG(dev, "rx submit --> %d\n", retval);
                 if (skb)
                         dev_kfree_skb_any(skb);
+                spin_lock_irqsave(&dev->req_lock, flags);
+                list_add(&req->list, &dev->rx_reqs);
+                spin_unlock_irqrestore(&dev->req_lock, flags);
         }
         return retval;
 }
 
 static void rx_complete(struct usb_ep *ep, struct usb_request *req)
 {
-        struct sk_buff  *skb = req->context;
+        struct sk_buff  *skb = req->context, *skb2;
         struct eth_dev  *dev = ep->driver_data;
         int             status = req->status;
-        bool            rx_queue = 0;
 
         switch (status) {
 
@@ -289,8 +288,30 @@ static void rx_complete(struct usb_ep *ep, struct usb_request *req)
                 } else {
                         skb_queue_tail(&dev->rx_frames, skb);
                 }
-                if (!status)
-                        rx_queue = 1;
+                skb = NULL;
+
+                skb2 = skb_dequeue(&dev->rx_frames);
+                while (skb2) {
+                        if (status < 0
+                                        || ETH_HLEN > skb2->len
+                                        || skb2->len > VLAN_ETH_FRAME_LEN) {
+                                dev->net->stats.rx_errors++;
+                                dev->net->stats.rx_length_errors++;
+                                DBG(dev, "rx length %d\n", skb2->len);
+                                dev_kfree_skb_any(skb2);
+                                goto next_frame;
+                        }
+                        skb2->protocol = eth_type_trans(skb2, dev->net);
+                        dev->net->stats.rx_packets++;
+                        dev->net->stats.rx_bytes += skb2->len;
+
+                        /* no buffer copies needed, unless hardware can't
+                         * use skb buffers.
+                         */
+                        status = netif_rx(skb2);
+next_frame:
+                        skb2 = skb_dequeue(&dev->rx_frames);
+                }
                 break;
 
         /* software-driven interface shutdown */
@@ -313,20 +334,22 @@ quiesce:
                 /* FALLTHROUGH */
 
         default:
-                rx_queue = 1;
-                dev_kfree_skb_any(skb);
                 dev->net->stats.rx_errors++;
                 DBG(dev, "rx status %d\n", status);
                 break;
         }
 
+        if (skb)
+                dev_kfree_skb_any(skb);
+        if (!netif_running(dev->net)) {
 clean:
                 spin_lock(&dev->req_lock);
                 list_add(&req->list, &dev->rx_reqs);
                 spin_unlock(&dev->req_lock);
-
-        if (rx_queue && likely(napi_schedule_prep(&dev->rx_napi)))
-                __napi_schedule(&dev->rx_napi);
+                req = NULL;
+        }
+        if (req)
+                rx_submit(dev, req, GFP_ATOMIC);
 }
 
 static int prealloc(struct list_head *list, struct usb_ep *ep, unsigned n)
@@ -391,24 +414,16 @@ static void rx_fill(struct eth_dev *dev, gfp_t gfp_flags)
 {
         struct usb_request      *req;
         unsigned long           flags;
-        int                     rx_counts = 0;
 
         /* fill unused rxq slots with some skb */
         spin_lock_irqsave(&dev->req_lock, flags);
         while (!list_empty(&dev->rx_reqs)) {
-
-                if (++rx_counts > qlen(dev->gadget, dev->qmult))
-                        break;
-
                 req = container_of(dev->rx_reqs.next,
                                 struct usb_request, list);
                 list_del_init(&req->list);
                 spin_unlock_irqrestore(&dev->req_lock, flags);
 
                 if (rx_submit(dev, req, gfp_flags) < 0) {
-                        spin_lock_irqsave(&dev->req_lock, flags);
-                        list_add(&req->list, &dev->rx_reqs);
-                        spin_unlock_irqrestore(&dev->req_lock, flags);
                         defer_kevent(dev, WORK_RX_MEMORY);
                         return;
                 }
@@ -418,41 +433,6 @@ static void rx_fill(struct eth_dev *dev, gfp_t gfp_flags)
         spin_unlock_irqrestore(&dev->req_lock, flags);
 }
 
-static int gether_poll(struct napi_struct *napi, int budget)
-{
-        struct eth_dev  *dev = container_of(napi, struct eth_dev, rx_napi);
-        struct sk_buff  *skb;
-        unsigned int    work_done = 0;
-        int             status = 0;
-
-        while ((skb = skb_dequeue(&dev->rx_frames))) {
-                if (status < 0
-                                || ETH_HLEN > skb->len
-                                || skb->len > VLAN_ETH_FRAME_LEN) {
-                        dev->net->stats.rx_errors++;
-                        dev->net->stats.rx_length_errors++;
-                        DBG(dev, "rx length %d\n", skb->len);
-                        dev_kfree_skb_any(skb);
-                        continue;
-                }
-                skb->protocol = eth_type_trans(skb, dev->net);
-                dev->net->stats.rx_packets++;
-                dev->net->stats.rx_bytes += skb->len;
-
-                status = netif_rx_ni(skb);
-        }
-
-        if (netif_running(dev->net)) {
-                rx_fill(dev, GFP_KERNEL);
-                work_done++;
-        }
-
-        if (work_done < budget)
-                napi_complete(&dev->rx_napi);
-
-        return work_done;
-}
-
 static void eth_work(struct work_struct *work)
 {
         struct eth_dev  *dev = container_of(work, struct eth_dev, work);
@@ -645,7 +625,6 @@ static void eth_start(struct eth_dev *dev, gfp_t gfp_flags)
         /* and open the tx floodgates */
         atomic_set(&dev->tx_qlen, 0);
         netif_wake_queue(dev->net);
-        napi_enable(&dev->rx_napi);
 }
 
 static int eth_open(struct net_device *net)
@@ -672,7 +651,6 @@ static int eth_stop(struct net_device *net)
         unsigned long   flags;
 
         VDBG(dev, "%s\n", __func__);
-        napi_disable(&dev->rx_napi);
         netif_stop_queue(net);
 
         DBG(dev, "stop stats: rx/tx %ld/%ld, errs %ld/%ld\n",
@@ -790,7 +768,6 @@ struct eth_dev *gether_setup_name(struct usb_gadget *g,
                 return ERR_PTR(-ENOMEM);
 
         dev = netdev_priv(net);
-        netif_napi_add(net, &dev->rx_napi, gether_poll, GETHER_NAPI_WEIGHT);
         spin_lock_init(&dev->lock);
         spin_lock_init(&dev->req_lock);
         INIT_WORK(&dev->work, eth_work);
@@ -853,7 +830,6 @@ struct net_device *gether_setup_name_default(const char *netname)
                 return ERR_PTR(-ENOMEM);
 
         dev = netdev_priv(net);
-        netif_napi_add(net, &dev->rx_napi, gether_poll, GETHER_NAPI_WEIGHT);
         spin_lock_init(&dev->lock);
         spin_lock_init(&dev->req_lock);
         INIT_WORK(&dev->work, eth_work);
@@ -1137,7 +1113,6 @@ void gether_disconnect(struct gether *link)
 {
         struct eth_dev          *dev = link->ioport;
         struct usb_request      *req;
-        struct sk_buff          *skb;
 
         WARN_ON(!dev);
         if (!dev)
@@ -1164,12 +1139,6 @@ void gether_disconnect(struct gether *link)
                 spin_lock(&dev->req_lock);
         }
         spin_unlock(&dev->req_lock);
-
-        spin_lock(&dev->rx_frames.lock);
-        while ((skb = __skb_dequeue(&dev->rx_frames)))
-                dev_kfree_skb_any(skb);
-        spin_unlock(&dev->rx_frames.lock);
-
         link->in_ep->driver_data = NULL;
         link->in_ep->desc = NULL;