Start/stop TTY on netdev open/close

This allows the ldisc to reset cleanly, and even after a UART error.
It also makes for a cleaner ldisc close().

diff --git a/module/elmcan.c b/module/elmcan.c
index 1ac12913d78b5f1466bbb8ff18e3ef827c87ec84..94d031a70ef10ca564433eae3530c27b9eec3a97 100644 (file)
--- a/module/elmcan.c
+++ b/module/elmcan.c
@@ -771,17 +771,19 @@ static int elmcan_netdev_open(struct net_device *dev)
        int err;
 
        spin_lock_bh(&elm->lock);
-       if (elm->uart_side_failure) {
-               netdev_err(elm->dev, "Refusing to open interface after a hardware fault has been detected.\n");
-               spin_unlock_bh(&elm->lock);
-               return -EIO;
-       }
 
        if (!elm->tty) {
                spin_unlock_bh(&elm->lock);
                return -ENODEV;
        }
 
+       if (elm->uart_side_failure)
+               netdev_warn(elm->dev, "Reopening netdev after a UART side fault has been detected.\n");
+
+       /* Clear TTY buffers */
+       elm->rxfill = 0;
+       elm->txleft = 0;
+
        /* open_candev() checks for elm->can.bittiming.bitrate != 0 */
        err = open_candev(dev);
        if (err) {
@@ -816,24 +818,19 @@ static int elmcan_netdev_close(struct net_device *dev)
 {
        struct elmcan *elm = netdev_priv(dev);
 
-       netif_stop_queue(dev);
-
+       /* Interrupt whatever the ELM327 is doing right now */
        spin_lock_bh(&elm->lock);
-       if (elm->tty) {
-               /* Interrupt whatever we're doing right now */
-               elm327_send(elm, ELM327_DUMMY_STRING, 1);
-
-               /* Clear the wakeup bit, as the netdev will be down and thus
-                * the wakeup handler won't clear it
-                */
-               clear_bit(TTY_DO_WRITE_WAKEUP, &elm->tty->flags);
+       elm327_send(elm, ELM327_DUMMY_STRING, 1);
+       spin_unlock_bh(&elm->lock);
 
-               spin_unlock_bh(&elm->lock);
+       /* Give UART one final chance to flush.
+        * This may netif_wake_queue(), so don't netif_stop_queue()
+        * before flushing the worker.
+        */
+       clear_bit(TTY_DO_WRITE_WAKEUP, &elm->tty->flags);
+       flush_work(&elm->tx_work);
 
-               flush_work(&elm->tx_work);
-       } else {
-               spin_unlock_bh(&elm->lock);
-       }
+       netif_stop_queue(dev);
 
        can_rx_offload_disable(&elm->offload);
        elm->can.state = CAN_STATE_STOPPED;
@@ -1066,7 +1063,6 @@ static int elmcan_ldisc_open(struct tty_struct *tty)
 
        /* Configure TTY interface */
        tty->receive_room = 65536; /* We don't flow control */
-       elm->txleft = 0; /* Clear TTY TX buffer */
        spin_lock_init(&elm->lock);
        INIT_WORK(&elm->tx_work, elmcan_ldisc_tx_worker);
 
@@ -1112,13 +1108,12 @@ static void elmcan_ldisc_close(struct tty_struct *tty)
 {
        struct elmcan *elm = (struct elmcan *)tty->disc_data;
 
-       /* unregister_netdev() calls .ndo_stop() so we don't have to. */
+       /* unregister_netdev() calls .ndo_stop() so we don't have to.
+        * Our .ndo_stop() also flushes the TTY write wakeup handler,
+        * so we can safely set elm->tty = NULL after this.
+        */
        unregister_candev(elm->dev);
 
-       /* Ensure that our worker won't be rescheduled */
-       clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
-       flush_work(&elm->tx_work);
-
        /* Mark channel as dead */
        spin_lock_bh(&elm->lock);
        tty->disc_data = NULL;