ravb: minimize TX data copying
Renesas Ethernet AVB controller requires that all data are aligned on 4-byte
boundary. While it's easily achievable for the RX data with the help of
skb_reserve() (we even align on 128-byte boundary as recommended by the manual),
we can't do the same with the TX data, and it always comes unaligned from
the networking core. Originally we solved it an easy way, copying all packet
to a preallocated aligned buffer; however, it's enough to copy only up to
3 first bytes from each packet, doing the transfer using 2 TX descriptors
instead of just 1. Here's an implementation of the new TX algorithm that
significantly reduces the driver's memory requirements.
Signed-off-by: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/ethernet/renesas/ravb_main.c b/drivers/net/ethernet/renesas/ravb_main.c
index 779bb58..3d972d8 100644
--- a/drivers/net/ethernet/renesas/ravb_main.c
+++ b/drivers/net/ethernet/renesas/ravb_main.c
@@ -195,12 +195,8 @@
priv->tx_skb[q] = NULL;
/* Free aligned TX buffers */
- if (priv->tx_buffers[q]) {
- for (i = 0; i < priv->num_tx_ring[q]; i++)
- kfree(priv->tx_buffers[q][i]);
- }
- kfree(priv->tx_buffers[q]);
- priv->tx_buffers[q] = NULL;
+ kfree(priv->tx_align[q]);
+ priv->tx_align[q] = NULL;
if (priv->rx_ring[q]) {
ring_size = sizeof(struct ravb_ex_rx_desc) *
@@ -212,7 +208,7 @@
if (priv->tx_ring[q]) {
ring_size = sizeof(struct ravb_tx_desc) *
- (priv->num_tx_ring[q] + 1);
+ (priv->num_tx_ring[q] * NUM_TX_DESC + 1);
dma_free_coherent(NULL, ring_size, priv->tx_ring[q],
priv->tx_desc_dma[q]);
priv->tx_ring[q] = NULL;
@@ -227,7 +223,8 @@
struct ravb_tx_desc *tx_desc;
struct ravb_desc *desc;
int rx_ring_size = sizeof(*rx_desc) * priv->num_rx_ring[q];
- int tx_ring_size = sizeof(*tx_desc) * priv->num_tx_ring[q];
+ int tx_ring_size = sizeof(*tx_desc) * priv->num_tx_ring[q] *
+ NUM_TX_DESC;
dma_addr_t dma_addr;
int i;
@@ -260,11 +257,12 @@
memset(priv->tx_ring[q], 0, tx_ring_size);
/* Build TX ring buffer */
- for (i = 0; i < priv->num_tx_ring[q]; i++) {
- tx_desc = &priv->tx_ring[q][i];
+ for (i = 0, tx_desc = priv->tx_ring[q]; i < priv->num_tx_ring[q];
+ i++, tx_desc++) {
+ tx_desc->die_dt = DT_EEMPTY;
+ tx_desc++;
tx_desc->die_dt = DT_EEMPTY;
}
- tx_desc = &priv->tx_ring[q][i];
tx_desc->dptr = cpu_to_le32((u32)priv->tx_desc_dma[q]);
tx_desc->die_dt = DT_LINKFIX; /* type */
@@ -285,7 +283,6 @@
struct ravb_private *priv = netdev_priv(ndev);
struct sk_buff *skb;
int ring_size;
- void *buffer;
int i;
/* Allocate RX and TX skb rings */
@@ -305,19 +302,11 @@
}
/* Allocate rings for the aligned buffers */
- priv->tx_buffers[q] = kcalloc(priv->num_tx_ring[q],
- sizeof(*priv->tx_buffers[q]), GFP_KERNEL);
- if (!priv->tx_buffers[q])
+ priv->tx_align[q] = kmalloc(DPTR_ALIGN * priv->num_tx_ring[q] +
+ DPTR_ALIGN - 1, GFP_KERNEL);
+ if (!priv->tx_align[q])
goto error;
- for (i = 0; i < priv->num_tx_ring[q]; i++) {
- buffer = kmalloc(PKT_BUF_SZ + RAVB_ALIGN - 1, GFP_KERNEL);
- if (!buffer)
- goto error;
- /* Aligned TX buffer */
- priv->tx_buffers[q][i] = buffer;
- }
-
/* Allocate all RX descriptors. */
ring_size = sizeof(struct ravb_ex_rx_desc) * (priv->num_rx_ring[q] + 1);
priv->rx_ring[q] = dma_alloc_coherent(NULL, ring_size,
@@ -329,7 +318,8 @@
priv->dirty_rx[q] = 0;
/* Allocate all TX descriptors. */
- ring_size = sizeof(struct ravb_tx_desc) * (priv->num_tx_ring[q] + 1);
+ ring_size = sizeof(struct ravb_tx_desc) *
+ (priv->num_tx_ring[q] * NUM_TX_DESC + 1);
priv->tx_ring[q] = dma_alloc_coherent(NULL, ring_size,
&priv->tx_desc_dma[q],
GFP_KERNEL);
@@ -443,7 +433,8 @@
u32 size;
for (; priv->cur_tx[q] - priv->dirty_tx[q] > 0; priv->dirty_tx[q]++) {
- entry = priv->dirty_tx[q] % priv->num_tx_ring[q];
+ entry = priv->dirty_tx[q] % (priv->num_tx_ring[q] *
+ NUM_TX_DESC);
desc = &priv->tx_ring[q][entry];
if (desc->die_dt != DT_FEMPTY)
break;
@@ -451,14 +442,18 @@
dma_rmb();
size = le16_to_cpu(desc->ds_tagl) & TX_DS;
/* Free the original skb. */
- if (priv->tx_skb[q][entry]) {
+ if (priv->tx_skb[q][entry / NUM_TX_DESC]) {
dma_unmap_single(&ndev->dev, le32_to_cpu(desc->dptr),
size, DMA_TO_DEVICE);
- dev_kfree_skb_any(priv->tx_skb[q][entry]);
- priv->tx_skb[q][entry] = NULL;
+ /* Last packet descriptor? */
+ if (entry % NUM_TX_DESC == NUM_TX_DESC - 1) {
+ entry /= NUM_TX_DESC;
+ dev_kfree_skb_any(priv->tx_skb[q][entry]);
+ priv->tx_skb[q][entry] = NULL;
+ stats->tx_packets++;
+ }
free_num++;
}
- stats->tx_packets++;
stats->tx_bytes += size;
desc->die_dt = DT_EEMPTY;
}
@@ -1284,37 +1279,53 @@
u32 dma_addr;
void *buffer;
u32 entry;
+ u32 len;
spin_lock_irqsave(&priv->lock, flags);
- if (priv->cur_tx[q] - priv->dirty_tx[q] >= priv->num_tx_ring[q]) {
+ if (priv->cur_tx[q] - priv->dirty_tx[q] > (priv->num_tx_ring[q] - 1) *
+ NUM_TX_DESC) {
netif_err(priv, tx_queued, ndev,
"still transmitting with the full ring!\n");
netif_stop_subqueue(ndev, q);
spin_unlock_irqrestore(&priv->lock, flags);
return NETDEV_TX_BUSY;
}
- entry = priv->cur_tx[q] % priv->num_tx_ring[q];
- priv->tx_skb[q][entry] = skb;
+ entry = priv->cur_tx[q] % (priv->num_tx_ring[q] * NUM_TX_DESC);
+ priv->tx_skb[q][entry / NUM_TX_DESC] = skb;
if (skb_put_padto(skb, ETH_ZLEN))
goto drop;
- buffer = PTR_ALIGN(priv->tx_buffers[q][entry], RAVB_ALIGN);
- memcpy(buffer, skb->data, skb->len);
- desc = &priv->tx_ring[q][entry];
- desc->ds_tagl = cpu_to_le16(skb->len);
- dma_addr = dma_map_single(&ndev->dev, buffer, skb->len, DMA_TO_DEVICE);
+ buffer = PTR_ALIGN(priv->tx_align[q], DPTR_ALIGN) +
+ entry / NUM_TX_DESC * DPTR_ALIGN;
+ len = PTR_ALIGN(skb->data, DPTR_ALIGN) - skb->data;
+ memcpy(buffer, skb->data, len);
+ dma_addr = dma_map_single(&ndev->dev, buffer, len, DMA_TO_DEVICE);
if (dma_mapping_error(&ndev->dev, dma_addr))
goto drop;
+
+ desc = &priv->tx_ring[q][entry];
+ desc->ds_tagl = cpu_to_le16(len);
+ desc->dptr = cpu_to_le32(dma_addr);
+
+ buffer = skb->data + len;
+ len = skb->len - len;
+ dma_addr = dma_map_single(&ndev->dev, buffer, len, DMA_TO_DEVICE);
+ if (dma_mapping_error(&ndev->dev, dma_addr))
+ goto unmap;
+
+ desc++;
+ desc->ds_tagl = cpu_to_le16(len);
desc->dptr = cpu_to_le32(dma_addr);
/* TX timestamp required */
if (q == RAVB_NC) {
ts_skb = kmalloc(sizeof(*ts_skb), GFP_ATOMIC);
if (!ts_skb) {
- dma_unmap_single(&ndev->dev, dma_addr, skb->len,
+ desc--;
+ dma_unmap_single(&ndev->dev, dma_addr, len,
DMA_TO_DEVICE);
- goto drop;
+ goto unmap;
}
ts_skb->skb = skb;
ts_skb->tag = priv->ts_skb_tag++;
@@ -1330,13 +1341,15 @@
/* Descriptor type must be set after all the above writes */
dma_wmb();
- desc->die_dt = DT_FSINGLE;
+ desc->die_dt = DT_FEND;
+ desc--;
+ desc->die_dt = DT_FSTART;
ravb_write(ndev, ravb_read(ndev, TCCR) | (TCCR_TSRQ0 << q), TCCR);
- priv->cur_tx[q]++;
- if (priv->cur_tx[q] - priv->dirty_tx[q] >= priv->num_tx_ring[q] &&
- !ravb_tx_free(ndev, q))
+ priv->cur_tx[q] += NUM_TX_DESC;
+ if (priv->cur_tx[q] - priv->dirty_tx[q] >
+ (priv->num_tx_ring[q] - 1) * NUM_TX_DESC && !ravb_tx_free(ndev, q))
netif_stop_subqueue(ndev, q);
exit:
@@ -1344,9 +1357,12 @@
spin_unlock_irqrestore(&priv->lock, flags);
return NETDEV_TX_OK;
+unmap:
+ dma_unmap_single(&ndev->dev, le32_to_cpu(desc->dptr),
+ le16_to_cpu(desc->ds_tagl), DMA_TO_DEVICE);
drop:
dev_kfree_skb_any(skb);
- priv->tx_skb[q][entry] = NULL;
+ priv->tx_skb[q][entry / NUM_TX_DESC] = NULL;
goto exit;
}