net: axienet: Factor out TX descriptor chain cleanup

Factor out the code that cleans up a number of connected TX descriptors,
as we will need it to properly roll back a failed _xmit() call.
There are subtle differences between cleaning up a successfully sent
chain (unknown number of involved descriptors, total data size needed)
and a chain that was about to set up (number of descriptors known), so
cater for those variations with some extra parameters.

Signed-off-by: Andre Przywara <andre.przywara@arm.com>
Reviewed-by: Radhey Shyam Pandey <radhey.shyam.pandey@xilinx.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/net/ethernet/xilinx/xilinx_axienet_main.c b/drivers/net/ethernet/xilinx/xilinx_axienet_main.c
index 82ec7de..5c1b539 100644 (file)
--- a/drivers/net/ethernet/xilinx/xilinx_axienet_main.c
+++ b/drivers/net/ethernet/xilinx/xilinx_axienet_main.c
@@ -545,32 +545,46 @@ static int axienet_device_reset(struct net_device *ndev)
 }
 
 /**
- * axienet_start_xmit_done - Invoked once a transmit is completed by the
- * Axi DMA Tx channel.
+ * axienet_free_tx_chain - Clean up a series of linked TX descriptors.
  * @ndev:      Pointer to the net_device structure
+ * @first_bd:  Index of first descriptor to clean up
+ * @nr_bds:    Number of descriptors to clean up, can be -1 if unknown.
+ * @sizep:     Pointer to a u32 filled with the total sum of all bytes
+ *             in all cleaned-up descriptors. Ignored if NULL.
  *
- * This function is invoked from the Axi DMA Tx isr to notify the completion
- * of transmit operation. It clears fields in the corresponding Tx BDs and
- * unmaps the corresponding buffer so that CPU can regain ownership of the
- * buffer. It finally invokes "netif_wake_queue" to restart transmission if
- * required.
+ * Would either be called after a successful transmit operation, or after
+ * there was an error when setting up the chain.
+ * Returns the number of descriptors handled.
  */
-static void axienet_start_xmit_done(struct net_device *ndev)
+static int axienet_free_tx_chain(struct net_device *ndev, u32 first_bd,
+                                int nr_bds, u32 *sizep)
 {
-       u32 size = 0;
-       u32 packets = 0;
        struct axienet_local *lp = netdev_priv(ndev);
        struct axidma_bd *cur_p;
-       unsigned int status = 0;
+       int max_bds = nr_bds;
+       unsigned int status;
+       int i;
+
+       if (max_bds == -1)
+               max_bds = lp->tx_bd_num;
+
+       for (i = 0; i < max_bds; i++) {
+               cur_p = &lp->tx_bd_v[(first_bd + i) % lp->tx_bd_num];
+               status = cur_p->status;
+
+               /* If no number is given, clean up *all* descriptors that have
+                * been completed by the MAC.
+                */
+               if (nr_bds == -1 && !(status & XAXIDMA_BD_STS_COMPLETE_MASK))
+                       break;
 
-       cur_p = &lp->tx_bd_v[lp->tx_bd_ci];
-       status = cur_p->status;
-       while (status & XAXIDMA_BD_STS_COMPLETE_MASK) {
                dma_unmap_single(ndev->dev.parent, cur_p->phys,
                                (cur_p->cntrl & XAXIDMA_BD_CTRL_LENGTH_MASK),
                                DMA_TO_DEVICE);
-               if (cur_p->skb)
+
+               if (cur_p->skb && (status & XAXIDMA_BD_STS_COMPLETE_MASK))
                        dev_consume_skb_irq(cur_p->skb);
+
                cur_p->cntrl = 0;
                cur_p->app0 = 0;
                cur_p->app1 = 0;
@@ -579,15 +593,36 @@ static void axienet_start_xmit_done(struct net_device *ndev)
                cur_p->status = 0;
                cur_p->skb = NULL;
 
-               size += status & XAXIDMA_BD_STS_ACTUAL_LEN_MASK;
-               packets++;
-
-               if (++lp->tx_bd_ci >= lp->tx_bd_num)
-                       lp->tx_bd_ci = 0;
-               cur_p = &lp->tx_bd_v[lp->tx_bd_ci];
-               status = cur_p->status;
+               if (sizep)
+                       *sizep += status & XAXIDMA_BD_STS_ACTUAL_LEN_MASK;
        }
 
+       return i;
+}
+
+/**
+ * axienet_start_xmit_done - Invoked once a transmit is completed by the
+ * Axi DMA Tx channel.
+ * @ndev:      Pointer to the net_device structure
+ *
+ * This function is invoked from the Axi DMA Tx isr to notify the completion
+ * of transmit operation. It clears fields in the corresponding Tx BDs and
+ * unmaps the corresponding buffer so that CPU can regain ownership of the
+ * buffer. It finally invokes "netif_wake_queue" to restart transmission if
+ * required.
+ */
+static void axienet_start_xmit_done(struct net_device *ndev)
+{
+       struct axienet_local *lp = netdev_priv(ndev);
+       u32 packets = 0;
+       u32 size = 0;
+
+       packets = axienet_free_tx_chain(ndev, lp->tx_bd_ci, -1, &size);
+
+       lp->tx_bd_ci += packets;
+       if (lp->tx_bd_ci >= lp->tx_bd_num)
+               lp->tx_bd_ci -= lp->tx_bd_num;
+
        ndev->stats.tx_packets += packets;
        ndev->stats.tx_bytes += size;