diff options
| author | Jonas Bonn <jonas@southpole.se> | 2010-11-25 02:30:32 +0000 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2010-11-28 11:16:38 -0800 |
| commit | 6a632625c7da7594d059b88dae0e9c591af147ba (patch) | |
| tree | d062b16340e3b2d10575ad06882cdbaa1c6014b5 | |
| parent | 4f64bcb2fc093a3a9d7d41220004491ce88e4dd3 (diff) | |
| download | lwn-6a632625c7da7594d059b88dae0e9c591af147ba.tar.gz lwn-6a632625c7da7594d059b88dae0e9c591af147ba.zip | |
ethoc: remove division from loops
Calculating the BD entry using a modulus operation isn't optimal, especially
inside the loop. This patch removes the modulus operations in favour of:
i) simply checking for wrapping in the case of cur_rx
ii) forcing num_tx to be a power of two and using it to mask out the
entry from cur_tx
The also prevents possible issues related overflow of the cur_rx and cur_tx
counters.
Signed-off-by: Jonas Bonn <jonas@southpole.se>
Signed-off-by: David S. Miller <davem@davemloft.net>
| -rw-r--r-- | drivers/net/ethoc.c | 17 |
1 files changed, 13 insertions, 4 deletions
diff --git a/drivers/net/ethoc.c b/drivers/net/ethoc.c index 93b50d674b1e..b79d7e1555d5 100644 --- a/drivers/net/ethoc.c +++ b/drivers/net/ethoc.c @@ -412,7 +412,7 @@ static int ethoc_rx(struct net_device *dev, int limit) unsigned int entry; struct ethoc_bd bd; - entry = priv->num_tx + (priv->cur_rx % priv->num_rx); + entry = priv->num_tx + priv->cur_rx; ethoc_read_bd(priv, entry, &bd); if (bd.stat & RX_BD_EMPTY) { ethoc_ack_irq(priv, INT_MASK_RX); @@ -456,7 +456,8 @@ static int ethoc_rx(struct net_device *dev, int limit) bd.stat &= ~RX_BD_STATS; bd.stat |= RX_BD_EMPTY; ethoc_write_bd(priv, entry, &bd); - priv->cur_rx++; + if (++priv->cur_rx == priv->num_rx) + priv->cur_rx = 0; } return count; @@ -503,7 +504,7 @@ static int ethoc_tx(struct net_device *dev, int limit) for (count = 0; count < limit; ++count) { unsigned int entry; - entry = priv->dty_tx % priv->num_tx; + entry = priv->dty_tx & (priv->num_tx-1); ethoc_read_bd(priv, entry, &bd); @@ -1000,9 +1001,17 @@ static int __devinit ethoc_probe(struct platform_device *pdev) /* calculate the number of TX/RX buffers, maximum 128 supported */ num_bd = min_t(unsigned int, 128, (netdev->mem_end - netdev->mem_start + 1) / ETHOC_BUFSIZ); - priv->num_tx = max(2, num_bd / 4); + if (num_bd < 4) { + ret = -ENODEV; + goto error; + } + /* num_tx must be a power of two */ + priv->num_tx = rounddown_pow_of_two(num_bd >> 1); priv->num_rx = num_bd - priv->num_tx; + dev_dbg(&pdev->dev, "ethoc: num_tx: %d num_rx: %d\n", + priv->num_tx, priv->num_rx); + priv->vma = devm_kzalloc(&pdev->dev, num_bd*sizeof(void*), GFP_KERNEL); if (!priv->vma) { ret = -ENOMEM; |