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Subject[PATCH 05/14] net: axienet: Factor out TX descriptor chain cleanup
Date
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>
---
.../net/ethernet/xilinx/xilinx_axienet_main.c | 75 ++++++++++++-------
1 file changed, 50 insertions(+), 25 deletions(-)

diff --git a/drivers/net/ethernet/xilinx/xilinx_axienet_main.c b/drivers/net/ethernet/xilinx/xilinx_axienet_main.c
index ec5d01adc1d5..82abe2b0f16a 100644
--- a/drivers/net/ethernet/xilinx/xilinx_axienet_main.c
+++ b/drivers/net/ethernet/xilinx/xilinx_axienet_main.c
@@ -543,33 +543,37 @@ static int axienet_device_reset(struct net_device *ndev)
return 0;
}

-/**
- * 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.
+/* Clean up a series of linked TX descriptors. 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);
+ int max_bds = (nr_bds != -1) ? nr_bds : lp->tx_bd_num;
struct axidma_bd *cur_p;
- unsigned int status = 0;
+ unsigned int status;
+ int i;
+
+ 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;
@@ -578,15 +582,36 @@ 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)
+{
+ u32 size = 0;
+ u32 packets = 0;
+ struct axienet_local *lp = netdev_priv(ndev);
+
+ 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;

--
2.17.1
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