@@ -109,7 +109,7 @@
#define TX_TIMEOUT (1*HZ)
-const char gfar_driver_version[] = "1.3";
+const char gfar_driver_version[] = "2.0";
static int gfar_enet_open(struct net_device *dev);
static int gfar_start_xmit(struct sk_buff *skb, struct net_device *dev);
@@ -207,6 +207,7 @@ static void gfar_init_bds(struct net_device *ndev)
rx_queue->next_to_clean = 0;
rx_queue->next_to_use = 0;
+ rx_queue->next_to_alloc = 0;
/* make sure next_to_clean != next_to_use after this
* by leaving at least 1 unused descriptor
@@ -222,7 +223,7 @@ static int gfar_alloc_skb_resources(struct net_device *ndev)
{
void *vaddr;
dma_addr_t addr;
- int i, j, k;
+ int i, j;
struct gfar_private *priv = netdev_priv(ndev);
struct device *dev = priv->dev;
struct gfar_priv_tx_q *tx_queue = NULL;
@@ -262,6 +263,7 @@ static int gfar_alloc_skb_resources(struct net_device *ndev)
rx_queue->rx_bd_base = vaddr;
rx_queue->rx_bd_dma_base = addr;
rx_queue->ndev = ndev;
+ rx_queue->dev = dev;
addr += sizeof(struct rxbd8) * rx_queue->rx_ring_size;
vaddr += sizeof(struct rxbd8) * rx_queue->rx_ring_size;
}
@@ -276,21 +278,17 @@ static int gfar_alloc_skb_resources(struct net_device *ndev)
if (!tx_queue->tx_skbuff)
goto cleanup;
- for (k = 0; k < tx_queue->tx_ring_size; k++)
- tx_queue->tx_skbuff[k] = NULL;
+ for (j = 0; j < tx_queue->tx_ring_size; j++)
+ tx_queue->tx_skbuff[j] = NULL;
}
for (i = 0; i < priv->num_rx_queues; i++) {
rx_queue = priv->rx_queue[i];
- rx_queue->rx_skbuff =
- kmalloc_array(rx_queue->rx_ring_size,
- sizeof(*rx_queue->rx_skbuff),
- GFP_KERNEL);
- if (!rx_queue->rx_skbuff)
+ rx_queue->rx_buff = kcalloc(rx_queue->rx_ring_size,
+ sizeof(*rx_queue->rx_buff),
+ GFP_KERNEL);
+ if (!rx_queue->rx_buff)
goto cleanup;
-
- for (j = 0; j < rx_queue->rx_ring_size; j++)
- rx_queue->rx_skbuff[j] = NULL;
}
gfar_init_bds(ndev);
@@ -335,10 +333,8 @@ static void gfar_init_rqprm(struct gfar_private *priv)
}
}
-static void gfar_rx_buff_size_config(struct gfar_private *priv)
+static void gfar_rx_offload_en(struct gfar_private *priv)
{
- int frame_size = priv->ndev->mtu + ETH_HLEN + ETH_FCS_LEN;
-
/* set this when rx hw offload (TOE) functions are being used */
priv->uses_rxfcb = 0;
@@ -347,16 +343,6 @@ static void gfar_rx_buff_size_config(struct gfar_private *priv)
if (priv->hwts_rx_en)
priv->uses_rxfcb = 1;
-
- if (priv->uses_rxfcb)
- frame_size += GMAC_FCB_LEN;
-
- frame_size += priv->padding;
-
- frame_size = (frame_size & ~(INCREMENTAL_BUFFER_SIZE - 1)) +
- INCREMENTAL_BUFFER_SIZE;
-
- priv->rx_buffer_size = frame_size;
}
static void gfar_mac_rx_config(struct gfar_private *priv)
@@ -590,7 +576,6 @@ static int gfar_alloc_rx_queues(struct gfar_private *priv)
if (!priv->rx_queue[i])
return -ENOMEM;
- priv->rx_queue[i]->rx_skbuff = NULL;
priv->rx_queue[i]->qindex = i;
priv->rx_queue[i]->ndev = priv->ndev;
}
@@ -1184,12 +1169,11 @@ void gfar_mac_reset(struct gfar_private *priv)
udelay(3);
- /* Compute rx_buff_size based on config flags */
- gfar_rx_buff_size_config(priv);
+ gfar_rx_offload_en(priv);
/* Initialize the max receive frame/buffer lengths */
- gfar_write(®s->maxfrm, priv->rx_buffer_size);
- gfar_write(®s->mrblr, priv->rx_buffer_size);
+ gfar_write(®s->maxfrm, GFAR_JUMBO_FRAME_SIZE);
+ gfar_write(®s->mrblr, GFAR_RXB_SIZE);
/* Initialize the Minimum Frame Length Register */
gfar_write(®s->minflr, MINFLR_INIT_SETTINGS);
@@ -1197,12 +1181,11 @@ void gfar_mac_reset(struct gfar_private *priv)
/* Initialize MACCFG2. */
tempval = MACCFG2_INIT_SETTINGS;
- /* If the mtu is larger than the max size for standard
- * ethernet frames (ie, a jumbo frame), then set maccfg2
- * to allow huge frames, and to check the length
+ /* eTSEC74 erratum: Rx frames of length MAXFRM or MAXFRM-1
+ * are marked as truncated. Avoid this by MACCFG2[Huge Frame]=1,
+ * and by checking RxBD[LG] and discarding larger than MAXFRM.
*/
- if (priv->rx_buffer_size > DEFAULT_RX_BUFFER_SIZE ||
- gfar_has_errata(priv, GFAR_ERRATA_74))
+ if (gfar_has_errata(priv, GFAR_ERRATA_74))
tempval |= MACCFG2_HUGEFRAME | MACCFG2_LENGTHCHECK;
gfar_write(®s->maccfg2, tempval);
@@ -1413,8 +1396,6 @@ static int gfar_probe(struct platform_device *ofdev)
priv->device_flags & FSL_GIANFAR_DEV_HAS_TIMER)
dev->needed_headroom = GMAC_FCB_LEN;
- priv->rx_buffer_size = DEFAULT_RX_BUFFER_SIZE;
-
/* Initializing some of the rx/tx queue level parameters */
for (i = 0; i < priv->num_tx_queues; i++) {
priv->tx_queue[i]->tx_ring_size = DEFAULT_TX_RING_SIZE;
@@ -1911,26 +1892,32 @@ static void free_skb_tx_queue(struct gfar_priv_tx_q *tx_queue)
static void free_skb_rx_queue(struct gfar_priv_rx_q *rx_queue)
{
- struct rxbd8 *rxbdp;
- struct gfar_private *priv = netdev_priv(rx_queue->ndev);
int i;
- rxbdp = rx_queue->rx_bd_base;
+ struct rxbd8 *rxbdp = rx_queue->rx_bd_base;
+
+ if (rx_queue->skb)
+ dev_kfree_skb(rx_queue->skb);
for (i = 0; i < rx_queue->rx_ring_size; i++) {
- if (rx_queue->rx_skbuff[i]) {
- dma_unmap_single(priv->dev, be32_to_cpu(rxbdp->bufPtr),
- priv->rx_buffer_size,
- DMA_FROM_DEVICE);
- dev_kfree_skb_any(rx_queue->rx_skbuff[i]);
- rx_queue->rx_skbuff[i] = NULL;
- }
+ struct gfar_rx_buff *rxb = &rx_queue->rx_buff[i];
+
rxbdp->lstatus = 0;
rxbdp->bufPtr = 0;
rxbdp++;
+
+ if (!rxb->page)
+ continue;
+
+ dma_unmap_single(rx_queue->dev, rxb->dma,
+ PAGE_SIZE, DMA_FROM_DEVICE);
+ __free_page(rxb->page);
+
+ rxb->page = NULL;
}
- kfree(rx_queue->rx_skbuff);
- rx_queue->rx_skbuff = NULL;
+
+ kfree(rx_queue->rx_buff);
+ rx_queue->rx_buff = NULL;
}
/* If there are any tx skbs or rx skbs still around, free them.
@@ -1955,7 +1942,7 @@ static void free_skb_resources(struct gfar_private *priv)
for (i = 0; i < priv->num_rx_queues; i++) {
rx_queue = priv->rx_queue[i];
- if (rx_queue->rx_skbuff)
+ if (rx_queue->rx_buff)
free_skb_rx_queue(rx_queue);
}
@@ -2513,7 +2500,7 @@ static int gfar_change_mtu(struct net_device *dev, int new_mtu)
struct gfar_private *priv = netdev_priv(dev);
int frame_size = new_mtu + ETH_HLEN;
- if ((frame_size < 64) || (frame_size > JUMBO_FRAME_SIZE)) {
+ if ((frame_size < 64) || (frame_size > GFAR_JUMBO_FRAME_SIZE)) {
netif_err(priv, drv, dev, "Invalid MTU setting\n");
return -EINVAL;
}
@@ -2567,15 +2554,6 @@ static void gfar_timeout(struct net_device *dev)
schedule_work(&priv->reset_task);
}
-static void gfar_align_skb(struct sk_buff *skb)
-{
- /* We need the data buffer to be aligned properly. We will reserve
- * as many bytes as needed to align the data properly
- */
- skb_reserve(skb, RXBUF_ALIGNMENT -
- (((unsigned long) skb->data) & (RXBUF_ALIGNMENT - 1)));
-}
-
/* Interrupt Handler for Transmit complete */
static void gfar_clean_tx_ring(struct gfar_priv_tx_q *tx_queue)
{
@@ -2682,28 +2660,27 @@ static void gfar_clean_tx_ring(struct gfar_priv_tx_q *tx_queue)
netdev_tx_completed_queue(txq, howmany, bytes_sent);
}
-static struct sk_buff *gfar_new_skb(struct net_device *ndev,
- dma_addr_t *bufaddr)
+static bool gfar_new_page(struct gfar_priv_rx_q *rxq, struct gfar_rx_buff *rxb)
{
- struct gfar_private *priv = netdev_priv(ndev);
- struct sk_buff *skb;
+ struct page *page;
dma_addr_t addr;
- skb = netdev_alloc_skb(ndev, priv->rx_buffer_size + RXBUF_ALIGNMENT);
- if (!skb)
- return NULL;
+ page = dev_alloc_page();
+ if (unlikely(!page))
+ return false;
- gfar_align_skb(skb);
+ addr = dma_map_page(rxq->dev, page, 0, PAGE_SIZE, DMA_FROM_DEVICE);
+ if (unlikely(dma_mapping_error(rxq->dev, addr))) {
+ __free_page(page);
- addr = dma_map_single(priv->dev, skb->data,
- priv->rx_buffer_size, DMA_FROM_DEVICE);
- if (unlikely(dma_mapping_error(priv->dev, addr))) {
- dev_kfree_skb_any(skb);
- return NULL;
+ return false;
}
- *bufaddr = addr;
- return skb;
+ rxb->dma = addr;
+ rxb->page = page;
+ rxb->page_offset = 0;
+
+ return true;
}
static void gfar_rx_alloc_err(struct gfar_priv_rx_q *rx_queue)
@@ -2718,41 +2695,40 @@ static void gfar_rx_alloc_err(struct gfar_priv_rx_q *rx_queue)
static void gfar_alloc_rx_buffs(struct gfar_priv_rx_q *rx_queue,
int alloc_cnt)
{
- struct net_device *ndev = rx_queue->ndev;
- struct rxbd8 *bdp, *base;
- dma_addr_t bufaddr;
+ struct rxbd8 *bdp;
+ struct gfar_rx_buff *rxb;
int i;
i = rx_queue->next_to_use;
- base = rx_queue->rx_bd_base;
bdp = &rx_queue->rx_bd_base[i];
+ rxb = &rx_queue->rx_buff[i];
while (alloc_cnt--) {
- struct sk_buff *skb = rx_queue->rx_skbuff[i];
-
- if (likely(!skb)) {
- skb = gfar_new_skb(ndev, &bufaddr);
- if (unlikely(!skb)) {
+ /* try reuse page */
+ if (unlikely(!rxb->page)) {
+ if (unlikely(!gfar_new_page(rx_queue, rxb))) {
gfar_rx_alloc_err(rx_queue);
break;
}
- } else { /* restore from sleep state */
- bufaddr = be32_to_cpu(bdp->bufPtr);
}
- rx_queue->rx_skbuff[i] = skb;
-
/* Setup the new RxBD */
- gfar_init_rxbdp(rx_queue, bdp, bufaddr);
+ gfar_init_rxbdp(rx_queue, bdp,
+ rxb->dma + rxb->page_offset + RXBUF_ALIGNMENT);
/* Update to the next pointer */
- bdp = next_bd(bdp, base, rx_queue->rx_ring_size);
+ bdp++;
+ rxb++;
- if (unlikely(++i == rx_queue->rx_ring_size))
+ if (unlikely(++i == rx_queue->rx_ring_size)) {
i = 0;
+ bdp = rx_queue->rx_bd_base;
+ rxb = rx_queue->rx_buff;
+ }
}
rx_queue->next_to_use = i;
+ rx_queue->next_to_alloc = i;
}
static void count_errors(u32 lstatus, struct net_device *ndev)
@@ -2839,6 +2815,93 @@ static irqreturn_t gfar_transmit(int irq, void *grp_id)
return IRQ_HANDLED;
}
+static bool gfar_add_rx_frag(struct gfar_rx_buff *rxb, u32 lstatus,
+ struct sk_buff *skb, bool first)
+{
+ unsigned int size = lstatus & BD_LENGTH_MASK;
+ struct page *page = rxb->page;
+
+ /* Remove the FCS from the packet length */
+ if (likely(lstatus & BD_LFLAG(RXBD_LAST)))
+ size -= ETH_FCS_LEN;
+
+ if (likely(first))
+ skb_put(skb, size);
+ else
+ skb_add_rx_frag(skb, skb_shinfo(skb)->nr_frags, page,
+ rxb->page_offset + RXBUF_ALIGNMENT,
+ size, GFAR_RXB_TRUESIZE);
+
+ /* try reuse page */
+ if (unlikely(page_count(page) != 1))
+ return false;
+
+ /* change offset to the other half */
+ rxb->page_offset ^= GFAR_RXB_TRUESIZE;
+
+ atomic_inc(&page->_count);
+
+ return true;
+}
+
+static void gfar_reuse_rx_page(struct gfar_priv_rx_q *rxq,
+ struct gfar_rx_buff *old_rxb)
+{
+ struct gfar_rx_buff *new_rxb;
+ u16 nta = rxq->next_to_alloc;
+
+ new_rxb = &rxq->rx_buff[nta];
+
+ /* find next buf that can reuse a page */
+ nta++;
+ rxq->next_to_alloc = (nta < rxq->rx_ring_size) ? nta : 0;
+
+ /* copy page reference */
+ *new_rxb = *old_rxb;
+
+ /* sync for use by the device */
+ dma_sync_single_range_for_device(rxq->dev, old_rxb->dma,
+ old_rxb->page_offset,
+ GFAR_RXB_TRUESIZE, DMA_FROM_DEVICE);
+}
+
+static struct sk_buff *gfar_get_next_rxbuff(struct gfar_priv_rx_q *rx_queue,
+ u32 lstatus, struct sk_buff *skb)
+{
+ struct gfar_rx_buff *rxb = &rx_queue->rx_buff[rx_queue->next_to_clean];
+ struct page *page = rxb->page;
+ bool first = false;
+
+ if (likely(!skb)) {
+ void *buff_addr = page_address(page) + rxb->page_offset;
+
+ skb = build_skb(buff_addr, GFAR_SKBFRAG_SIZE);
+ if (unlikely(!skb)) {
+ gfar_rx_alloc_err(rx_queue);
+ return NULL;
+ }
+ skb_reserve(skb, RXBUF_ALIGNMENT);
+ first = true;
+ }
+
+ dma_sync_single_range_for_cpu(rx_queue->dev, rxb->dma, rxb->page_offset,
+ GFAR_RXB_TRUESIZE, DMA_FROM_DEVICE);
+
+ if (gfar_add_rx_frag(rxb, lstatus, skb, first)) {
+ /* reuse the free half of the page */
+ gfar_reuse_rx_page(rx_queue, rxb);
+ } else {
+ /* page cannot be reused, unmap it */
+ dma_unmap_page(rx_queue->dev, rxb->dma,
+ PAGE_SIZE, DMA_FROM_DEVICE);
+ }
+
+ /* clear rxb content */
+ rxb->page = NULL;
+
+ return skb;
+}
+
static inline void gfar_rx_checksum(struct sk_buff *skb, struct rxfcb *fcb)
{
/* If valid headers were found, and valid sums
@@ -2902,14 +2965,14 @@ static void gfar_process_frame(struct net_device *ndev, struct sk_buff *skb)
int gfar_clean_rx_ring(struct gfar_priv_rx_q *rx_queue, int rx_work_limit)
{
struct net_device *ndev = rx_queue->ndev;
- struct rxbd8 *bdp, *base;
- struct sk_buff *skb;
+ struct gfar_private *priv = netdev_priv(ndev);
+ struct rxbd8 *bdp;
int i, howmany = 0;
+ struct sk_buff *skb = rx_queue->skb;
int cleaned_cnt = gfar_rxbd_unused(rx_queue);
- struct gfar_private *priv = netdev_priv(ndev);
+ unsigned int total_bytes = 0, total_pkts = 0;
/* Get the first full descriptor */
- base = rx_queue->rx_bd_base;
i = rx_queue->next_to_clean;
while (rx_work_limit--) {
@@ -2929,54 +2992,51 @@ int gfar_clean_rx_ring(struct gfar_priv_rx_q *rx_queue, int rx_work_limit)
rmb();
/* fetch next to clean buffer from the ring */
- skb = rx_queue->rx_skbuff[i];
+ skb = gfar_get_next_rxbuff(rx_queue, lstatus, skb);
+ if (unlikely(!skb))
+ break;
- dma_unmap_single(priv->dev, be32_to_cpu(bdp->bufPtr),
- priv->rx_buffer_size, DMA_FROM_DEVICE);
+ cleaned_cnt++;
+ howmany++;
- if (unlikely(!(lstatus & BD_LFLAG(RXBD_ERR)) &&
- (lstatus & BD_LENGTH_MASK) > priv->rx_buffer_size))
- lstatus |= BD_LFLAG(RXBD_LARGE);
+ if (unlikely(++i == rx_queue->rx_ring_size))
+ i = 0;
+
+ rx_queue->next_to_clean = i;
+
+ /* fetch next buffer if not the last in frame */
+ if (!(lstatus & BD_LFLAG(RXBD_LAST)))
+ continue;
- if (unlikely(!(lstatus & BD_LFLAG(RXBD_LAST)) ||
- (lstatus & BD_LFLAG(RXBD_ERR)))) {
+ if (unlikely(lstatus & BD_LFLAG(RXBD_ERR))) {
count_errors(lstatus, ndev);
/* discard faulty buffer */
dev_kfree_skb(skb);
+ skb = NULL;
+ rx_queue->stats.rx_dropped++;
+ continue;
+ }
- } else {
- /* Increment the number of packets */
- rx_queue->stats.rx_packets++;
- howmany++;
-
- if (likely(skb)) {
- int pkt_len = (lstatus & BD_LENGTH_MASK) -
- ETH_FCS_LEN;
- /* Remove the FCS from the packet length */
- skb_put(skb, pkt_len);
- rx_queue->stats.rx_bytes += pkt_len;
- skb_record_rx_queue(skb, rx_queue->qindex);
- gfar_process_frame(ndev, skb);
-
- /* Send the packet up the stack */
- napi_gro_receive(&rx_queue->grp->napi_rx, skb);
+ /* Increment the number of packets */
+ total_pkts++;
+ total_bytes += skb->len;
- } else {
- netif_warn(priv, rx_err, ndev, "Missing skb!\n");
- rx_queue->stats.rx_dropped++;
- atomic64_inc(&priv->extra_stats.rx_skbmissing);
- }
+ skb_record_rx_queue(skb, rx_queue->qindex);
- }
+ gfar_process_frame(ndev, skb);
- rx_queue->rx_skbuff[i] = NULL;
- cleaned_cnt++;
- if (unlikely(++i == rx_queue->rx_ring_size))
- i = 0;
+ /* Send the packet up the stack */
+ napi_gro_receive(&rx_queue->grp->napi_rx, skb);
+
+ skb = NULL;
}
- rx_queue->next_to_clean = i;
+ /* Store incomplete frames for completion */
+ rx_queue->skb = skb;
+
+ rx_queue->stats.rx_packets += total_pkts;
+ rx_queue->stats.rx_bytes += total_bytes;
if (cleaned_cnt)
gfar_alloc_rx_buffs(rx_queue, cleaned_cnt);
@@ -71,11 +71,6 @@ struct ethtool_rx_list {
/* Number of bytes to align the rx bufs to */
#define RXBUF_ALIGNMENT 64
-/* The number of bytes which composes a unit for the purpose of
- * allocating data buffers. ie-for any given MTU, the data buffer
- * will be the next highest multiple of 512 bytes. */
-#define INCREMENTAL_BUFFER_SIZE 512
-
#define PHY_INIT_TIMEOUT 100000
#define DRV_NAME "gfar-enet"
@@ -105,11 +100,14 @@ extern const char gfar_driver_version[];
#define DEFAULT_RX_LFC_THR 16
#define DEFAULT_LFC_PTVVAL 4
-#define DEFAULT_RX_BUFFER_SIZE 1536
+#define GFAR_RXB_SIZE 1536
+#define GFAR_SKBFRAG_SIZE (RXBUF_ALIGNMENT + GFAR_RXB_SIZE \
+ + SKB_DATA_ALIGN(sizeof(struct skb_shared_info)))
+#define GFAR_RXB_TRUESIZE 2048
+
#define TX_RING_MOD_MASK(size) (size-1)
#define RX_RING_MOD_MASK(size) (size-1)
-#define JUMBO_BUFFER_SIZE 9728
-#define JUMBO_FRAME_SIZE 9600
+#define GFAR_JUMBO_FRAME_SIZE 9600
#define DEFAULT_FIFO_TX_THR 0x100
#define DEFAULT_FIFO_TX_STARVE 0x40
@@ -654,7 +652,6 @@ struct gfar_extra_stats {
atomic64_t eberr;
atomic64_t tx_babt;
atomic64_t tx_underrun;
- atomic64_t rx_skbmissing;
atomic64_t tx_timeout;
};
@@ -1015,9 +1012,15 @@ struct rx_q_stats {
unsigned long rx_dropped;
};
+struct gfar_rx_buff {
+ dma_addr_t dma;
+ struct page *page;
+ unsigned int page_offset;
+};
+
/**
* struct gfar_priv_rx_q - per rx queue structure
- * @rx_skbuff: skb pointers
+ * @rx_buff: Array of buffer info metadata structs
* @rx_bd_base: First rx buffer descriptor
* @next_to_use: index of the next buffer to be alloc'd
* @next_to_clean: index of the next buffer to be cleaned
@@ -1029,14 +1032,17 @@ struct rx_q_stats {
*/
struct gfar_priv_rx_q {
- struct sk_buff **rx_skbuff __aligned(SMP_CACHE_BYTES);
+ struct gfar_rx_buff *rx_buff __aligned(SMP_CACHE_BYTES);
struct rxbd8 *rx_bd_base;
struct net_device *ndev;
- struct gfar_priv_grp *grp;
+ struct device *dev;
u16 rx_ring_size;
u16 qindex;
+ struct gfar_priv_grp *grp;
u16 next_to_clean;
u16 next_to_use;
+ u16 next_to_alloc;
+ struct sk_buff *skb;
struct rx_q_stats stats;
u32 __iomem *rfbptr;
unsigned char rxcoalescing;
@@ -1111,7 +1117,6 @@ struct gfar_private {
struct device *dev;
struct net_device *ndev;
enum gfar_errata errata;
- unsigned int rx_buffer_size;
u16 uses_rxfcb;
u16 padding;
@@ -74,7 +74,6 @@ static const char stat_gstrings[][ETH_GSTRING_LEN] = {
"ethernet-bus-error",
"tx-babbling-errors",
"tx-underrun-errors",
- "rx-skb-missing-errors",
"tx-timeout-errors",
/* rmon stats */
"tx-rx-64-frames",
The eTSEC h/w is capable of scatter/gather on the receive side too if MAXFRM > MRBLR, when the allowed maximum Rx frame size is set to be greater than the maximum Rx buffer size (MRBLR). It's about time the driver makes use of this h/w capability, by supporting fixed buffer sizes and Rx S/G. The buffer size given to eTSEC for reception is fixed to 1536B (must be multiple of 64), which is the same default buffer size as before, used to accommodate standard MTU (1500B) size frames. As before, eTSEC can receive frames of up to 9600B. Individual Rx buffers are mapped to page halves (page size for eTSEC systems is 4KB). The skb is built around the first buffer of a frame (using build_skb()). In case the frame spans multiple buffers, the trailing buffers are added as Rx fragments to the skb. The last buffer in frame is marked by the L status flag. A mechanism is in place to reuse the pages owned by the driver (for Rx) for subsequent receptions. Supporting fixed size buffers allows the implementation of Rx S/G, which in turn removes the memory pressure issues the driver had before when MTU was set for jumbo frame reception. Also, in most cases, the Rx path becomes faster due to Rx page reusal, since the overhead of allocating new rx buffers is removed from the fast path. Signed-off-by: Claudiu Manoil <claudiu.manoil@freescale.com> --- v2: use lstatus as u32 consistently drivers/net/ethernet/freescale/gianfar.c | 320 ++++++++++++++--------- drivers/net/ethernet/freescale/gianfar.h | 31 ++- drivers/net/ethernet/freescale/gianfar_ethtool.c | 1 - 3 files changed, 208 insertions(+), 144 deletions(-)