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Commit 287be12e authored by Matt Carlson's avatar Matt Carlson Committed by David S. Miller
Browse files

tg3: Clarify rx buffer relationships 



This patch attempts to document the various rx buffer sizes used by the
driver and how they relate to each other.

Signed-off-by: default avatarMatt Carlson <mcarlson@broadcom.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 8f666b07

drivers/net/tg3.c

+23 −19
Original line number Diff line number Diff line
@@ -125,8 +125,15 @@ 
				 TG3_TX_RING_SIZE)

#define NEXT_TX(N)		(((N) + 1) & (TG3_TX_RING_SIZE - 1))



#define RX_PKT_BUF_SZ		(1536 + tp->rx_offset + 64)

#define RX_JUMBO_PKT_BUF_SZ	(9046 + tp->rx_offset + 64)

#define TG3_DMA_BYTE_ENAB		64



#define TG3_RX_STD_DMA_SZ		1536

#define TG3_RX_JMB_DMA_SZ		9046



#define TG3_RX_DMA_TO_MAP_SZ(x)		((x) + TG3_DMA_BYTE_ENAB)



#define TG3_RX_STD_MAP_SZ		TG3_RX_DMA_TO_MAP_SZ(TG3_RX_STD_DMA_SZ)

#define TG3_RX_JMB_MAP_SZ		TG3_RX_DMA_TO_MAP_SZ(TG3_RX_JMB_DMA_SZ)



/* minimum number of free TX descriptors required to wake up TX process */

#define TG3_TX_WAKEUP_THRESH(tp)		((tp)->tx_pending / 4)
@@ -4354,7 +4361,7 @@ static int tg3_alloc_rx_skb(struct tg3 *tp, u32 opaque_key, 
		map = &tp->rx_std_buffers[dest_idx];

		if (src_idx >= 0)

			src_map = &tp->rx_std_buffers[src_idx];

		skb_size = tp->rx_pkt_buf_sz;

		skb_size = tp->rx_pkt_map_sz;

		break;



	case RXD_OPAQUE_RING_JUMBO:
@@ -4363,7 +4370,7 @@ static int tg3_alloc_rx_skb(struct tg3 *tp, u32 opaque_key, 
		map = &tp->rx_jumbo_buffers[dest_idx];

		if (src_idx >= 0)

			src_map = &tp->rx_jumbo_buffers[src_idx];

		skb_size = RX_JUMBO_PKT_BUF_SZ;

		skb_size = TG3_RX_JMB_MAP_SZ;

		break;



	default:
@@ -4376,14 +4383,13 @@ static int tg3_alloc_rx_skb(struct tg3 *tp, u32 opaque_key, 
	 * Callers depend upon this behavior and assume that

	 * we leave everything unchanged if we fail.

	 */

	skb = netdev_alloc_skb(tp->dev, skb_size);

	skb = netdev_alloc_skb(tp->dev, skb_size + tp->rx_offset);

	if (skb == NULL)

		return -ENOMEM;



	skb_reserve(skb, tp->rx_offset);



	mapping = pci_map_single(tp->pdev, skb->data,

				 skb_size - tp->rx_offset,

	mapping = pci_map_single(tp->pdev, skb->data, skb_size,

				 PCI_DMA_FROMDEVICE);



	map->skb = skb;
@@ -4540,8 +4546,7 @@ static int tg3_rx(struct tg3 *tp, int budget) 
			if (skb_size < 0)

				goto drop_it;



			pci_unmap_single(tp->pdev, dma_addr,

					 skb_size - tp->rx_offset,

			pci_unmap_single(tp->pdev, dma_addr, skb_size,

					 PCI_DMA_FROMDEVICE);



			skb_put(skb, len);
@@ -5531,7 +5536,7 @@ static void tg3_free_rings(struct tg3 *tp) 
			continue;

		pci_unmap_single(tp->pdev,

				 pci_unmap_addr(rxp, mapping),

				 tp->rx_pkt_buf_sz - tp->rx_offset,

				 tp->rx_pkt_map_sz,

				 PCI_DMA_FROMDEVICE);

		dev_kfree_skb_any(rxp->skb);

		rxp->skb = NULL;
@@ -5544,7 +5549,7 @@ static void tg3_free_rings(struct tg3 *tp) 
			continue;

		pci_unmap_single(tp->pdev,

				 pci_unmap_addr(rxp, mapping),

				 RX_JUMBO_PKT_BUF_SZ - tp->rx_offset,

				 TG3_RX_JMB_MAP_SZ,

				 PCI_DMA_FROMDEVICE);

		dev_kfree_skb_any(rxp->skb);

		rxp->skb = NULL;
@@ -5581,7 +5586,7 @@ static void tg3_free_rings(struct tg3 *tp) 
 */

static int tg3_init_rings(struct tg3 *tp)

{

	u32 i;

	u32 i, rx_pkt_dma_sz;



	/* Free up all the SKBs. */

	tg3_free_rings(tp);
@@ -5592,10 +5597,11 @@ static int tg3_init_rings(struct tg3 *tp) 
	memset(tp->rx_rcb, 0, TG3_RX_RCB_RING_BYTES(tp));

	memset(tp->tx_ring, 0, TG3_TX_RING_BYTES);



	tp->rx_pkt_buf_sz = RX_PKT_BUF_SZ;

	rx_pkt_dma_sz = TG3_RX_STD_DMA_SZ;

	if ((tp->tg3_flags2 & TG3_FLG2_5780_CLASS) &&

	    (tp->dev->mtu > ETH_DATA_LEN))

		tp->rx_pkt_buf_sz = RX_JUMBO_PKT_BUF_SZ;

	    tp->dev->mtu > ETH_DATA_LEN)

		rx_pkt_dma_sz = TG3_RX_JMB_DMA_SZ;

	tp->rx_pkt_map_sz = TG3_RX_DMA_TO_MAP_SZ(rx_pkt_dma_sz);



	/* Initialize invariants of the rings, we only set this

	 * stuff once.  This works because the card does not
@@ -5605,8 +5611,7 @@ static int tg3_init_rings(struct tg3 *tp) 
		struct tg3_rx_buffer_desc *rxd;



		rxd = &tp->rx_std[i];

		rxd->idx_len = (tp->rx_pkt_buf_sz - tp->rx_offset - 64)

			<< RXD_LEN_SHIFT;

		rxd->idx_len = rx_pkt_dma_sz << RXD_LEN_SHIFT;

		rxd->type_flags = (RXD_FLAG_END << RXD_FLAGS_SHIFT);

		rxd->opaque = (RXD_OPAQUE_RING_STD |

			       (i << RXD_OPAQUE_INDEX_SHIFT));
@@ -5617,8 +5622,7 @@ static int tg3_init_rings(struct tg3 *tp) 
			struct tg3_rx_buffer_desc *rxd;



			rxd = &tp->rx_jumbo[i];

			rxd->idx_len = (RX_JUMBO_PKT_BUF_SZ - tp->rx_offset - 64)

				<< RXD_LEN_SHIFT;

			rxd->idx_len = TG3_RX_JMB_DMA_SZ << RXD_LEN_SHIFT;

			rxd->type_flags = (RXD_FLAG_END << RXD_FLAGS_SHIFT) |

				RXD_FLAG_JUMBO;

			rxd->opaque = (RXD_OPAQUE_RING_JUMBO |

drivers/net/tg3.h

+1 −1
Original line number Diff line number Diff line
@@ -2571,7 +2571,7 @@ struct tg3 { 
	struct tg3_rx_buffer_desc	*rx_rcb;

	dma_addr_t			rx_rcb_mapping;



	u32				rx_pkt_buf_sz;

	u32				rx_pkt_map_sz;



	/* begin "everything else" cacheline(s) section */

	struct net_device_stats		net_stats;