net: fec: fix the error to get the previous BD entry

Bug: error to get the previous BD entry. When the current BD
is the first BD, the previous BD entry must be the last BD,
not "bdp - 1" in current logic.

V4:
  * Optimize fec_enet_get_nextdesc() for code clean.
    Replace "ex_new_bd - ring_size" with "ex_base".
    Replace "new_bd - ring_size" with "base".

V3:
  * Restore the API name because David suggest to use fec_enet_
    prefix for all function in fec driver.
    So, change next_bd() -> fec_enet_get_nextdesc()
        change pre_bd()  -> fec_enet_get_prevdesc()
    * Reduce the two APIs parameters for easy to call.

V2:
  * Add tx_ring_size and rx_ring_size to struct fec_enet_private.
  * Replace api fec_enet_get_nextdesc() with next_bd().
    Replace api fec_enet_get_prevdesc() with pre_bd().

  * Move all ring size check logic to next_bd() and pre_bd(), which
    simplifies the code redundancy.

V1:
  * Add BD ring size check to get the previous BD entry in correctly.

Reviewed-by: Li Frank <B20596@freescale.com>
Signed-off-by: Fugang Duan  <B38611@freescale.com>
Acked-by: Frank Li <frank.li@freescale.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 66 insertions, 36 deletions

diff --git a/drivers/net/ethernet/freescale/fec_main.c b/drivers/net/ethernet/freescale/fec_main.c
index f49f43fef2aa..c0a531db1dbf 100644
--- a/drivers/net/ethernet/freescale/fec_main.c
+++ b/drivers/net/ethernet/freescale/fec_main.c
@@ -214,22 +214,63 @@ MODULE_PARM_DESC(macaddr, "FEC Ethernet MAC address");
 
 static int mii_cnt;
 
-static struct bufdesc *fec_enet_get_nextdesc(struct bufdesc *bdp, int is_ex)
+static inline
+struct bufdesc *fec_enet_get_nextdesc(struct bufdesc *bdp,
+        struct fec_enet_private *fep, int queue_id)
 {
-        struct bufdesc_ex *ex = (struct bufdesc_ex *)bdp;
-        if (is_ex)
-                return (struct bufdesc *)(ex + 1);
+        struct bufdesc *new_bd = bdp + 1;
+        struct bufdesc_ex *ex_new_bd = (struct bufdesc_ex *)bdp + 1;
+        struct fec_enet_priv_tx_q *tx_queue = fep->tx_queue[queue_id];
+        struct fec_enet_priv_rx_q *rx_queue = fep->rx_queue[queue_id];
+        struct bufdesc_ex *ex_base;
+        struct bufdesc *base;
+        int ring_size;
+
+        if (bdp >= tx_queue->tx_bd_base) {
+                base = tx_queue->tx_bd_base;
+                ring_size = tx_queue->tx_ring_size;
+                ex_base = (struct bufdesc_ex *)tx_queue->tx_bd_base;
+        } else {
+                base = rx_queue->rx_bd_base;
+                ring_size = rx_queue->rx_ring_size;
+                ex_base = (struct bufdesc_ex *)rx_queue->rx_bd_base;
+        }
+
+        if (fep->bufdesc_ex)
+                return (struct bufdesc *)((ex_new_bd >= (ex_base + ring_size)) ?
+                        ex_base : ex_new_bd);
         else
-                return bdp + 1;
+                return (new_bd >= (base + ring_size)) ?
+                        base : new_bd;
 }
 
-static struct bufdesc *fec_enet_get_prevdesc(struct bufdesc *bdp, int is_ex)
+static inline
+struct bufdesc *fec_enet_get_prevdesc(struct bufdesc *bdp,
+        struct fec_enet_private *fep, int queue_id)
 {
-        struct bufdesc_ex *ex = (struct bufdesc_ex *)bdp;
-        if (is_ex)
-                return (struct bufdesc *)(ex - 1);
+        struct bufdesc *new_bd = bdp - 1;
+        struct bufdesc_ex *ex_new_bd = (struct bufdesc_ex *)bdp - 1;
+        struct fec_enet_priv_tx_q *tx_queue = fep->tx_queue[queue_id];
+        struct fec_enet_priv_rx_q *rx_queue = fep->rx_queue[queue_id];
+        struct bufdesc_ex *ex_base;
+        struct bufdesc *base;
+        int ring_size;
+
+        if (bdp >= tx_queue->tx_bd_base) {
+                base = tx_queue->tx_bd_base;
+                ring_size = tx_queue->tx_ring_size;
+                ex_base = (struct bufdesc_ex *)tx_queue->tx_bd_base;
+        } else {
+                base = rx_queue->rx_bd_base;
+                ring_size = rx_queue->rx_ring_size;
+                ex_base = (struct bufdesc_ex *)rx_queue->rx_bd_base;
+        }
+
+        if (fep->bufdesc_ex)
+                return (struct bufdesc *)((ex_new_bd < ex_base) ?
+                        (ex_new_bd + ring_size) : ex_new_bd);
         else
-                return bdp - 1;
+                return (new_bd < base) ? (new_bd + ring_size) : new_bd;
 }
 
 static void *swap_buffer(void *bufaddr, int len)
@@ -372,7 +413,7 @@ fec_enet_start_xmit(struct sk_buff *skb, struct net_device *ndev)
                         | BD_ENET_TX_LAST | BD_ENET_TX_TC);
         bdp->cbd_sc = status;
 
-        bdp_pre = fec_enet_get_prevdesc(bdp, fep->bufdesc_ex);
+        bdp_pre = fec_enet_get_prevdesc(bdp, fep, queue);
         if ((id_entry->driver_data & FEC_QUIRK_ERR006358) &&
             !(bdp_pre->cbd_sc & BD_ENET_TX_READY)) {
                 fep->delay_work.trig_tx = queue + 1;
@@ -381,10 +422,7 @@ fec_enet_start_xmit(struct sk_buff *skb, struct net_device *ndev)
         }
 
         /* If this was the last BD in the ring, start at the beginning again. */
-        if (status & BD_ENET_TX_WRAP)
-                bdp = txq->tx_bd_base;
-        else
-                bdp = fec_enet_get_nextdesc(bdp, fep->bufdesc_ex);
+        bdp = fec_enet_get_nextdesc(bdp, fep, queue);
 
         skb_tx_timestamp(skb);
 
@@ -426,11 +464,11 @@ static void fec_enet_bd_init(struct net_device *dev)
                                 bdp->cbd_sc = BD_ENET_RX_EMPTY;
                         else
                                 bdp->cbd_sc = 0;
-                        bdp = fec_enet_get_nextdesc(bdp, fep->bufdesc_ex);
+                        bdp = fec_enet_get_nextdesc(bdp, fep, i);
                 }
 
                 /* Set the last buffer to wrap */
-                bdp = fec_enet_get_prevdesc(bdp, fep->bufdesc_ex);
+                bdp = fec_enet_get_prevdesc(bdp, fep, i);
                 bdp->cbd_sc |= BD_SC_WRAP;
 
                 rx_queue->cur_rx = rx_queue->rx_bd_base;
@@ -451,11 +489,11 @@ static void fec_enet_bd_init(struct net_device *dev)
                                 tx_queue->tx_skbuff[i] = NULL;
                         }
                         bdp->cbd_bufaddr = 0;
-                        bdp = fec_enet_get_nextdesc(bdp, fep->bufdesc_ex);
+                        bdp = fec_enet_get_nextdesc(bdp, fep, i);
                 }
 
                 /* Set the last buffer to wrap */
-                bdp = fec_enet_get_prevdesc(bdp, fep->bufdesc_ex);
+                bdp = fec_enet_get_prevdesc(bdp, fep, i);
                 bdp->cbd_sc |= BD_SC_WRAP;
                 tx_queue->dirty_tx = bdp;
         }
@@ -816,10 +854,7 @@ fec_enet_tx(struct net_device *ndev)
                 bdp = txq->dirty_tx;
 
                 /* get next bdp of dirty_tx */
-                if (bdp->cbd_sc & BD_ENET_TX_WRAP)
-                        bdp = txq->tx_bd_base;
-                else
-                        bdp = fec_enet_get_nextdesc(bdp, fep->bufdesc_ex);
+                bdp = fec_enet_get_nextdesc(bdp, fep, queue_id);
 
                 while (((status = bdp->cbd_sc) & BD_ENET_TX_READY) == 0) {
 
@@ -889,10 +924,7 @@ fec_enet_tx(struct net_device *ndev)
                         txq->dirty_tx = bdp;
 
                         /* Update pointer to next buffer descriptor to be transmitted */
-                        if (status & BD_ENET_TX_WRAP)
-                                bdp = txq->tx_bd_base;
-                        else
-                                bdp = fec_enet_get_nextdesc(bdp, fep->bufdesc_ex);
+                        bdp = fec_enet_get_nextdesc(bdp, fep, queue_id);
 
                         /* Since we have freed up a buffer, the ring is no longer full
                          */
@@ -1098,10 +1130,8 @@ rx_processing_done:
                         }
 
                         /* Update BD pointer to next entry */
-                        if (status & BD_ENET_RX_WRAP)
-                                bdp = rxq->rx_bd_base;
-                        else
-                                bdp = fec_enet_get_nextdesc(bdp, fep->bufdesc_ex);
+                        bdp = fec_enet_get_nextdesc(bdp, fep, queue_id);
+
                         /* Doing this here will keep the FEC running while we process
                          * incoming frames.  On a heavily loaded network, we should be
                          * able to keep up at the expense of system resources.
@@ -1961,7 +1991,7 @@ static void fec_enet_free_buffers(struct net_device *ndev)
                                                 DMA_FROM_DEVICE);
                         if (skb)
                                 dev_kfree_skb(skb);
-                        bdp = fec_enet_get_nextdesc(bdp, fep->bufdesc_ex);
+                        bdp = fec_enet_get_nextdesc(bdp, fep, j);
                 }
         }
 
@@ -2013,11 +2043,11 @@ static int fec_enet_alloc_buffers(struct net_device *ndev)
                                 ebdp->cbd_esc = BD_ENET_RX_INT;
                         }
 
-                        bdp = fec_enet_get_nextdesc(bdp, fep->bufdesc_ex);
+                        bdp = fec_enet_get_nextdesc(bdp, fep, j);
                 }
 
                 /* Set the last buffer to wrap. */
-                bdp = fec_enet_get_prevdesc(bdp, fep->bufdesc_ex);
+                bdp = fec_enet_get_prevdesc(bdp, fep, j);
                 bdp->cbd_sc |= BD_SC_WRAP;
         }
 
@@ -2043,11 +2073,11 @@ static int fec_enet_alloc_buffers(struct net_device *ndev)
                                 ebdp->cbd_esc = BD_ENET_TX_INT;
                         }
 
-                        bdp = fec_enet_get_nextdesc(bdp, fep->bufdesc_ex);
+                        bdp = fec_enet_get_nextdesc(bdp, fep, j);
                 }
 
                 /* Set the last buffer to wrap. */
-                bdp = fec_enet_get_prevdesc(bdp, fep->bufdesc_ex);
+                bdp = fec_enet_get_prevdesc(bdp, fep, j);
                 bdp->cbd_sc |= BD_SC_WRAP;
         }