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: Matt Carlson <mcarlson@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/net/tg3.c b/drivers/net/tg3.c
index 5e74a19..a2a5f31 100644 (file)
--- a/drivers/net/tg3.c
+++ b/drivers/net/tg3.c
@@ -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 |

diff --git a/drivers/net/tg3.h b/drivers/net/tg3.h
index 5efae2c..d029b4b 100644 (file)
--- a/drivers/net/tg3.h
+++ b/drivers/net/tg3.h
@@ -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;