ucc_geth: Fix hangs after switching from full to half duplex

MPC8360 QE UCC ethernet controllers hang when changing link duplex
under a load (a bit of NFS activity is enough).

  PHY: mdio@e0102120:00 - Link is Up - 1000/Full
  sh-3.00# ethtool -s eth0 speed 100 duplex half autoneg off
  PHY: mdio@e0102120:00 - Link is Down
  PHY: mdio@e0102120:00 - Link is Up - 100/Half
  NETDEV WATCHDOG: eth0 (ucc_geth): transmit queue 0 timed out
  ------------[ cut here ]------------
  Badness at c01fcbd0 [verbose debug info unavailable]
  NIP: c01fcbd0 LR: c01fcbd0 CTR: c0194e44
  ...

The cure is to disable the controller before changing speed/duplex
and enable it afterwards.

Though, disabling the controller might take quite a while, so we
better not grab any spinlocks in adjust_link(). Instead, we quiesce
the driver's activity, and only then disable the controller.

Signed-off-by: Anton Vorontsov <avorontsov@ru.mvista.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 31 insertions, 5 deletions

diff --git a/drivers/net/ucc_geth.c b/drivers/net/ucc_geth.c
index a39368a46352..4469f2451a6f 100644
--- a/drivers/net/ucc_geth.c
+++ b/drivers/net/ucc_geth.c
@@ -1561,6 +1561,25 @@ static int ugeth_disable(struct ucc_geth_private *ugeth, enum comm_dir mode)
         return 0;
 }
 
+static void ugeth_quiesce(struct ucc_geth_private *ugeth)
+{
+        /* Wait for and prevent any further xmits. */
+        netif_tx_disable(ugeth->ndev);
+
+        /* Disable the interrupt to avoid NAPI rescheduling. */
+        disable_irq(ugeth->ug_info->uf_info.irq);
+
+        /* Stop NAPI, and possibly wait for its completion. */
+        napi_disable(&ugeth->napi);
+}
+
+static void ugeth_activate(struct ucc_geth_private *ugeth)
+{
+        napi_enable(&ugeth->napi);
+        enable_irq(ugeth->ug_info->uf_info.irq);
+        netif_tx_wake_all_queues(ugeth->ndev);
+}
+
 /* Called every time the controller might need to be made
  * aware of new link state.  The PHY code conveys this
  * information through variables in the ugeth structure, and this
@@ -1574,14 +1593,11 @@ static void adjust_link(struct net_device *dev)
         struct ucc_geth __iomem *ug_regs;
         struct ucc_fast __iomem *uf_regs;
         struct phy_device *phydev = ugeth->phydev;
-        unsigned long flags;
         int new_state = 0;
 
         ug_regs = ugeth->ug_regs;
         uf_regs = ugeth->uccf->uf_regs;
 
-        spin_lock_irqsave(&ugeth->lock, flags);
-
         if (phydev->link) {
                 u32 tempval = in_be32(&ug_regs->maccfg2);
                 u32 upsmr = in_be32(&uf_regs->upsmr);
@@ -1632,9 +1648,21 @@ static void adjust_link(struct net_device *dev)
                         ugeth->oldspeed = phydev->speed;
                 }
 
+                /*
+                 * To change the MAC configuration we need to disable the
+                 * controller. To do so, we have to either grab ugeth->lock,
+                 * which is a bad idea since 'graceful stop' commands might
+                 * take quite a while, or we can quiesce driver's activity.
+                 */
+                ugeth_quiesce(ugeth);
+                ugeth_disable(ugeth, COMM_DIR_RX_AND_TX);
+
                 out_be32(&ug_regs->maccfg2, tempval);
                 out_be32(&uf_regs->upsmr, upsmr);
 
+                ugeth_enable(ugeth, COMM_DIR_RX_AND_TX);
+                ugeth_activate(ugeth);
+
                 if (!ugeth->oldlink) {
                         new_state = 1;
                         ugeth->oldlink = 1;
@@ -1648,8 +1676,6 @@ static void adjust_link(struct net_device *dev)
 
         if (new_state && netif_msg_link(ugeth))
                 phy_print_status(phydev);
-
-        spin_unlock_irqrestore(&ugeth->lock, flags);
 }
 
 /* Initialize TBI PHY interface for communicating with the