Commit 6a632625 authored by Jonas Bonn's avatar Jonas Bonn Committed by David S. Miller
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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: default avatarJonas Bonn <jonas@southpole.se>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 4f64bcb2

drivers/net/ethoc.c

+13 −4
Original line number Diff line number Diff line
@@ -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;