[RFC][PATCH] net: fs_enet: fix tx error handling

[Mans Rullgard]

In some cases, the TXE flag is apparently set without any error
indication in the buffer descriptor status. When this happens, tx
stalls until the tx_restart() function is called via the device
watchdog which can take a long time.

To fix this, check for TXE in the napi poll function and trigger a
tx_restart() call as for errors reported in the buffer descriptor.

This change makes the FCC based Ethernet controller on MPC82xx devices
usable. It probably breaks the other modes (FEC, SCC) which I have no
way of testing.

Signed-off-by: Mans Rullgard <m...@mansr.com>
---
 .../ethernet/freescale/fs_enet/fs_enet-main.c | 47 +++++++------------
 .../net/ethernet/freescale/fs_enet/mac-fcc.c  |  2 +-
 2 files changed, 19 insertions(+), 30 deletions(-)

diff --git a/drivers/net/ethernet/freescale/fs_enet/fs_enet-main.c 
b/drivers/net/ethernet/freescale/fs_enet/fs_enet-main.c
index 78e008b81374..4276becd07cf 100644
--- a/drivers/net/ethernet/freescale/fs_enet/fs_enet-main.c
+++ b/drivers/net/ethernet/freescale/fs_enet/fs_enet-main.c
@@ -94,14 +94,22 @@ static int fs_enet_napi(struct napi_struct *napi, int 
budget)
        int curidx;
        int dirtyidx, do_wake, do_restart;
        int tx_left = TX_RING_SIZE;
+       u32 int_events;
 
        spin_lock(&fep->tx_lock);
        bdp = fep->dirty_tx;
+       do_wake = do_restart = 0;
+
+       int_events = (*fep->ops->get_int_events)(dev);
+
+       if (int_events & fep->ev_err) {
+               (*fep->ops->ev_error)(dev, int_events);
+               do_restart = 1;
+       }
 
        /* clear status bits for napi*/
        (*fep->ops->napi_clear_event)(dev);
 
-       do_wake = do_restart = 0;
        while (((sc = CBDR_SC(bdp)) & BD_ENET_TX_READY) == 0 && tx_left) {
                dirtyidx = bdp - fep->tx_bd_base;
 
@@ -318,43 +326,24 @@ fs_enet_interrupt(int irq, void *dev_id)
 {
        struct net_device *dev = dev_id;
        struct fs_enet_private *fep;
-       const struct fs_platform_info *fpi;
        u32 int_events;
-       u32 int_clr_events;
-       int nr, napi_ok;
-       int handled;
 
        fep = netdev_priv(dev);
-       fpi = fep->fpi;
 
-       nr = 0;
-       while ((int_events = (*fep->ops->get_int_events)(dev)) != 0) {
-               nr++;
+       int_events = (*fep->ops->get_int_events)(dev);
+       if (!int_events)
+               return IRQ_NONE;
 
-               int_clr_events = int_events;
-               int_clr_events &= ~fep->ev_napi;
+       int_events &= ~fep->ev_napi;
 
-               (*fep->ops->clear_int_events)(dev, int_clr_events);
-
-               if (int_events & fep->ev_err)
-                       (*fep->ops->ev_error)(dev, int_events);
-
-               if (int_events & fep->ev) {
-                       napi_ok = napi_schedule_prep(&fep->napi);
-
-                       (*fep->ops->napi_disable)(dev);
-                       (*fep->ops->clear_int_events)(dev, fep->ev_napi);
-
-                       /* NOTE: it is possible for FCCs in NAPI mode    */
-                       /* to submit a spurious interrupt while in poll  */
-                       if (napi_ok)
-                               __napi_schedule(&fep->napi);
-               }
+       (*fep->ops->clear_int_events)(dev, int_events);
 
+       if (napi_schedule_prep(&fep->napi)) {
+               (*fep->ops->napi_disable)(dev);
+               __napi_schedule(&fep->napi);
        }
 
-       handled = nr > 0;
-       return IRQ_RETVAL(handled);
+       return IRQ_HANDLED;
 }
 
 void fs_init_bds(struct net_device *dev)
diff --git a/drivers/net/ethernet/freescale/fs_enet/mac-fcc.c 
b/drivers/net/ethernet/freescale/fs_enet/mac-fcc.c
index b47490be872c..66c8f82a8333 100644
--- a/drivers/net/ethernet/freescale/fs_enet/mac-fcc.c
+++ b/drivers/net/ethernet/freescale/fs_enet/mac-fcc.c
@@ -124,7 +124,7 @@ static int do_pd_setup(struct fs_enet_private *fep)
        return ret;
 }
 
-#define FCC_NAPI_EVENT_MSK     (FCC_ENET_RXF | FCC_ENET_RXB | FCC_ENET_TXB)
+#define FCC_NAPI_EVENT_MSK     (FCC_ENET_RXF | FCC_ENET_RXB | FCC_ENET_TXB | 
FCC_ENET_TXE)
 #define FCC_EVENT              (FCC_ENET_RXF | FCC_ENET_TXB)
 #define FCC_ERR_EVENT_MSK      (FCC_ENET_TXE)
 
-- 
2.35.1