gianfar: Make all BD status writes 32-bit

Whenever we want to update the status field in a BD, we usually want to
update the length field, too.  By combining them into one 32-bit field, we
reduce the number of stores to memory shared with the controller, and we
eliminate the need for order-enforcement, as the length and "READY" bit are
now updated atomically at the same time.

Signed-off-by: Dai Haruki <Dai.Haruki@freescale.com>
Signed-off-by: Andy Fleming <afleming@freescale.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 31 insertions, 25 deletions

diff --git a/drivers/net/gianfar.c b/drivers/net/gianfar.c
index e7e8201283a3..3e611a69df13 100644
--- a/drivers/net/gianfar.c
+++ b/drivers/net/gianfar.c
@@ -854,8 +854,7 @@ static void free_skb_resources(struct gfar_private *priv)
                                 priv->rx_skbuff[i] = NULL;
                         }
 
-                        rxbdp->status = 0;
-                        rxbdp->length = 0;
+                        rxbdp->lstatus = 0;
                         rxbdp->bufPtr = 0;
 
                         rxbdp++;
@@ -976,8 +975,7 @@ int startup_gfar(struct net_device *dev)
         /* Initialize Transmit Descriptor Ring */
         txbdp = priv->tx_bd_base;
         for (i = 0; i < priv->tx_ring_size; i++) {
-                txbdp->status = 0;
-                txbdp->length = 0;
+                txbdp->lstatus = 0;
                 txbdp->bufPtr = 0;
                 txbdp++;
         }
@@ -1216,7 +1214,7 @@ static int gfar_start_xmit(struct sk_buff *skb, struct net_device *dev)
         struct gfar_private *priv = netdev_priv(dev);
         struct txfcb *fcb = NULL;
         struct txbd8 *txbdp, *base;
-        u16 status;
+        u32 lstatus;
         unsigned long flags;
 
         /* Update transmit stats */
@@ -1230,26 +1228,25 @@ static int gfar_start_xmit(struct sk_buff *skb, struct net_device *dev)
         base = priv->tx_bd_base;
 
         /* Clear all but the WRAP status flags */
-        status = txbdp->status & TXBD_WRAP;
+        lstatus = txbdp->lstatus & BD_LFLAG(TXBD_WRAP);
 
         /* Set up checksumming */
         if (CHECKSUM_PARTIAL == skb->ip_summed) {
                 fcb = gfar_add_fcb(skb);
-                status |= TXBD_TOE;
+                lstatus |= BD_LFLAG(TXBD_TOE);
                 gfar_tx_checksum(skb, fcb);
         }
 
         if (priv->vlgrp && vlan_tx_tag_present(skb)) {
                 if (unlikely(NULL == fcb)) {
                         fcb = gfar_add_fcb(skb);
-                        status |= TXBD_TOE;
+                        lstatus |= BD_LFLAG(TXBD_TOE);
                 }
 
                 gfar_tx_vlan(skb, fcb);
         }
 
         /* Set buffer length and pointer */
-        txbdp->length = skb->len;
         txbdp->bufPtr = dma_map_single(&dev->dev, skb->data,
                         skb->len, DMA_TO_DEVICE);
 
@@ -1260,12 +1257,10 @@ static int gfar_start_xmit(struct sk_buff *skb, struct net_device *dev)
         priv->skb_curtx =
             (priv->skb_curtx + 1) & TX_RING_MOD_MASK(priv->tx_ring_size);
 
-        /* Flag the BD as interrupt-causing */
-        status |= TXBD_INTERRUPT;
-
-        /* Flag the BD as ready to go, last in frame, and  */
-        /* in need of CRC */
-        status |= (TXBD_READY | TXBD_LAST | TXBD_CRC);
+        /* Flag the BD as ready, interrupt-causing, last, and in need of CRC */
+        lstatus |=
+                BD_LFLAG(TXBD_READY | TXBD_LAST | TXBD_CRC | TXBD_INTERRUPT) |
+                skb->len;
 
         dev->trans_start = jiffies;
 
@@ -1278,7 +1273,7 @@ static int gfar_start_xmit(struct sk_buff *skb, struct net_device *dev)
          */
 
         eieio();
-        txbdp->status = status;
+        txbdp->lstatus = lstatus;
 
         txbdp = next_bd(txbdp, base, priv->tx_ring_size);
 
@@ -1546,20 +1541,19 @@ static void gfar_new_rxbdp(struct net_device *dev, struct rxbd8 *bdp,
                 struct sk_buff *skb)
 {
         struct gfar_private *priv = netdev_priv(dev);
-        u32 * status_len = (u32 *)bdp;
-        u16 flags;
+        u32 lstatus;
 
         bdp->bufPtr = dma_map_single(&dev->dev, skb->data,
                         priv->rx_buffer_size, DMA_FROM_DEVICE);
 
-        flags = RXBD_EMPTY | RXBD_INTERRUPT;
+        lstatus = BD_LFLAG(RXBD_EMPTY | RXBD_INTERRUPT);
 
         if (bdp == priv->rx_bd_base + priv->rx_ring_size - 1)
-                flags |= RXBD_WRAP;
+                lstatus |= BD_LFLAG(RXBD_WRAP);
 
         eieio();
 
-        *status_len = (u32)flags << 16;
+        bdp->lstatus = lstatus;
 }
 
 
diff --git a/drivers/net/gianfar.h b/drivers/net/gianfar.h
index 1ebf7ac27a3d..9c8974dc8dd5 100644
--- a/drivers/net/gianfar.h
+++ b/drivers/net/gianfar.h
@@ -311,6 +311,8 @@ extern const char gfar_driver_version[];
 #define ATTRELI_EI_MASK         0x00003fff
 #define ATTRELI_EI(x) (x)
 
+#define BD_LFLAG(flags) ((flags) << 16)
+#define BD_LENGTH_MASK          0x00ff
 
 /* TxBD status field bits */
 #define TXBD_READY              0x8000
@@ -374,8 +376,13 @@ extern const char gfar_driver_version[];
 
 struct txbd8
 {
-        u16     status; /* Status Fields */
-        u16     length; /* Buffer length */
+        union {
+                struct {
+                        u16     status; /* Status Fields */
+                        u16     length; /* Buffer length */
+                };
+                u32 lstatus;
+        };
         u32     bufPtr; /* Buffer Pointer */
 };
 
@@ -390,8 +397,13 @@ struct txfcb {
 
 struct rxbd8
 {
-        u16     status; /* Status Fields */
-        u16     length; /* Buffer Length */
+        union {
+                struct {
+                        u16     status; /* Status Fields */
+                        u16     length; /* Buffer Length */
+                };
+                u32 lstatus;
+        };
         u32     bufPtr; /* Buffer Pointer */
 };