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Subject[PATCH 3.16 016/294] net: bcmgenet: Fix unmapping of fragments in bcmgenet_xmit()
3.16.50-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Doug Berger <opendmb@gmail.com>

commit 876dbadd53a7102e2a84afc84ea2bd3ee6dc5636 upstream.

In case we fail to map a single fragment, we would be leaving the
transmit ring populated with stale entries.

This commit introduces the helper function bcmgenet_put_txcb()
which takes care of rewinding the per-ring write pointer back to
where we left.

It also consolidates the functionality of bcmgenet_xmit_single()
and bcmgenet_xmit_frag() into the bcmgenet_xmit() function to
make the unmapping of control blocks cleaner.

Fixes: 1c1008c793fa ("net: bcmgenet: add main driver file")
Suggested-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: Doug Berger <opendmb@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
[bwh: Backported to 3.16:
- There's no tx_dma_failed statistic
- Adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
drivers/net/ethernet/broadcom/genet/bcmgenet.c | 191 +++++++++++--------------
1 file changed, 85 insertions(+), 106 deletions(-)

--- a/drivers/net/ethernet/broadcom/genet/bcmgenet.c
+++ b/drivers/net/ethernet/broadcom/genet/bcmgenet.c
@@ -900,6 +900,23 @@ static struct enet_cb *bcmgenet_get_txcb
return tx_cb_ptr;
}

+static struct enet_cb *bcmgenet_put_txcb(struct bcmgenet_priv *priv,
+ struct bcmgenet_tx_ring *ring)
+{
+ struct enet_cb *tx_cb_ptr;
+
+ tx_cb_ptr = ring->cbs;
+ tx_cb_ptr += ring->write_ptr - ring->cb_ptr;
+
+ /* Rewinding local write pointer */
+ if (ring->write_ptr == ring->cb_ptr)
+ ring->write_ptr = ring->end_ptr;
+ else
+ ring->write_ptr--;
+
+ return tx_cb_ptr;
+}
+
/* Simple helper to free a control block's resources */
static void bcmgenet_free_cb(struct enet_cb *cb)
{
@@ -1030,93 +1047,6 @@ static void bcmgenet_tx_reclaim_all(stru
bcmgenet_tx_reclaim(dev, &priv->tx_rings[DESC_INDEX]);
}

-/* Transmits a single SKB (either head of a fragment or a single SKB)
- * caller must hold priv->lock
- */
-static int bcmgenet_xmit_single(struct net_device *dev,
- struct sk_buff *skb,
- u16 dma_desc_flags,
- struct bcmgenet_tx_ring *ring)
-{
- struct bcmgenet_priv *priv = netdev_priv(dev);
- struct device *kdev = &priv->pdev->dev;
- struct enet_cb *tx_cb_ptr;
- unsigned int skb_len;
- dma_addr_t mapping;
- u32 length_status;
- int ret;
-
- tx_cb_ptr = bcmgenet_get_txcb(priv, ring);
-
- if (unlikely(!tx_cb_ptr))
- BUG();
-
- tx_cb_ptr->skb = skb;
-
- skb_len = skb_headlen(skb);
-
- mapping = dma_map_single(kdev, skb->data, skb_len, DMA_TO_DEVICE);
- ret = dma_mapping_error(kdev, mapping);
- if (ret) {
- netif_err(priv, tx_err, dev, "Tx DMA map failed\n");
- dev_kfree_skb(skb);
- return ret;
- }
-
- dma_unmap_addr_set(tx_cb_ptr, dma_addr, mapping);
- dma_unmap_len_set(tx_cb_ptr, dma_len, skb_len);
- length_status = (skb_len << DMA_BUFLENGTH_SHIFT) | dma_desc_flags |
- (priv->hw_params->qtag_mask << DMA_TX_QTAG_SHIFT) |
- DMA_TX_APPEND_CRC;
-
- if (skb->ip_summed == CHECKSUM_PARTIAL)
- length_status |= DMA_TX_DO_CSUM;
-
- dmadesc_set(priv, tx_cb_ptr->bd_addr, mapping, length_status);
-
- return 0;
-}
-
-/* Transmit a SKB fragement */
-static int bcmgenet_xmit_frag(struct net_device *dev,
- skb_frag_t *frag,
- u16 dma_desc_flags,
- struct bcmgenet_tx_ring *ring)
-{
- struct bcmgenet_priv *priv = netdev_priv(dev);
- struct device *kdev = &priv->pdev->dev;
- struct enet_cb *tx_cb_ptr;
- unsigned int frag_size;
- dma_addr_t mapping;
- int ret;
-
- tx_cb_ptr = bcmgenet_get_txcb(priv, ring);
-
- if (unlikely(!tx_cb_ptr))
- BUG();
-
- tx_cb_ptr->skb = NULL;
-
- frag_size = skb_frag_size(frag);
-
- mapping = skb_frag_dma_map(kdev, frag, 0, frag_size, DMA_TO_DEVICE);
- ret = dma_mapping_error(kdev, mapping);
- if (ret) {
- netif_err(priv, tx_err, dev, "%s: Tx DMA map failed\n",
- __func__);
- return ret;
- }
-
- dma_unmap_addr_set(tx_cb_ptr, dma_addr, mapping);
- dma_unmap_len_set(tx_cb_ptr, dma_len, frag_size);
-
- dmadesc_set(priv, tx_cb_ptr->bd_addr, mapping,
- (frag_size << DMA_BUFLENGTH_SHIFT) | dma_desc_flags |
- (priv->hw_params->qtag_mask << DMA_TX_QTAG_SHIFT));
-
- return 0;
-}
-
/* Reallocate the SKB to put enough headroom in front of it and insert
* the transmit checksum offsets in the descriptors
*/
@@ -1182,11 +1112,16 @@ static int bcmgenet_put_tx_csum(struct n
static netdev_tx_t bcmgenet_xmit(struct sk_buff *skb, struct net_device *dev)
{
struct bcmgenet_priv *priv = netdev_priv(dev);
+ struct device *kdev = &priv->pdev->dev;
struct bcmgenet_tx_ring *ring = NULL;
+ struct enet_cb *tx_cb_ptr;
struct netdev_queue *txq;
unsigned long flags = 0;
int nr_frags, index;
- u16 dma_desc_flags;
+ dma_addr_t mapping;
+ unsigned int size;
+ skb_frag_t *frag;
+ u32 len_stat;
int ret;
int i;

@@ -1235,26 +1170,48 @@ static netdev_tx_t bcmgenet_xmit(struct
}
}

- dma_desc_flags = DMA_SOP;
- if (nr_frags == 0)
- dma_desc_flags |= DMA_EOP;
-
- /* Transmit single SKB or head of fragment list */
- ret = bcmgenet_xmit_single(dev, skb, dma_desc_flags, ring);
- if (ret) {
- ret = NETDEV_TX_OK;
- goto out;
- }
+ for (i = 0; i <= nr_frags; i++) {
+ tx_cb_ptr = bcmgenet_get_txcb(priv, ring);

- /* xmit fragment */
- for (i = 0; i < nr_frags; i++) {
- ret = bcmgenet_xmit_frag(dev,
- &skb_shinfo(skb)->frags[i],
- (i == nr_frags - 1) ? DMA_EOP : 0, ring);
+ if (unlikely(!tx_cb_ptr))
+ BUG();
+
+ if (!i) {
+ /* Transmit single SKB or head of fragment list */
+ tx_cb_ptr->skb = skb;
+ size = skb_headlen(skb);
+ mapping = dma_map_single(kdev, skb->data, size,
+ DMA_TO_DEVICE);
+ } else {
+ /* xmit fragment */
+ tx_cb_ptr->skb = NULL;
+ frag = &skb_shinfo(skb)->frags[i - 1];
+ size = skb_frag_size(frag);
+ mapping = skb_frag_dma_map(kdev, frag, 0, size,
+ DMA_TO_DEVICE);
+ }
+
+ ret = dma_mapping_error(kdev, mapping);
if (ret) {
+ netif_err(priv, tx_err, dev, "Tx DMA map failed\n");
ret = NETDEV_TX_OK;
- goto out;
+ goto out_unmap_frags;
}
+ dma_unmap_addr_set(tx_cb_ptr, dma_addr, mapping);
+ dma_unmap_len_set(tx_cb_ptr, dma_len, size);
+
+ len_stat = (size << DMA_BUFLENGTH_SHIFT) |
+ (priv->hw_params->qtag_mask << DMA_TX_QTAG_SHIFT);
+
+ if (!i) {
+ len_stat |= DMA_TX_APPEND_CRC | DMA_SOP;
+ if (skb->ip_summed == CHECKSUM_PARTIAL)
+ len_stat |= DMA_TX_DO_CSUM;
+ }
+ if (i == nr_frags)
+ len_stat |= DMA_EOP;
+
+ dmadesc_set(priv, tx_cb_ptr->bd_addr, mapping, len_stat);
}

skb_tx_timestamp(skb);
@@ -1276,6 +1233,30 @@ out:
spin_unlock_irqrestore(&ring->lock, flags);

return ret;
+
+out_unmap_frags:
+ /* Back up for failed control block mapping */
+ bcmgenet_put_txcb(priv, ring);
+
+ /* Unmap successfully mapped control blocks */
+ while (i-- > 0) {
+ tx_cb_ptr = bcmgenet_put_txcb(priv, ring);
+ if (tx_cb_ptr->skb)
+ dma_unmap_single(kdev,
+ dma_unmap_addr(tx_cb_ptr, dma_addr),
+ dma_unmap_len(tx_cb_ptr, dma_len),
+ DMA_TO_DEVICE);
+ else
+ dma_unmap_page(kdev,
+ dma_unmap_addr(tx_cb_ptr, dma_addr),
+ dma_unmap_len(tx_cb_ptr, dma_len),
+ DMA_TO_DEVICE);
+ dma_unmap_addr_set(tx_cb_ptr, dma_addr, 0);
+ tx_cb_ptr->skb = NULL;
+ }
+
+ dev_kfree_skb(skb);
+ goto out;
}

static struct sk_buff *bcmgenet_rx_refill(struct bcmgenet_priv *priv,
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