Re: [PATCH 1/2 v2] mv643xx_eth: use sw csum for big packets

From: Lennert Buytenhek
Date: Thu Jun 10 2010 - 02:43:50 EST


On Wed, Jun 09, 2010 at 11:51:23AM +0300, Saeed Bishara wrote:

> diff --git a/drivers/net/mv643xx_eth.c b/drivers/net/mv643xx_eth.c
> index e345ec8..2d0e06b 100644
> --- a/drivers/net/mv643xx_eth.c
> +++ b/drivers/net/mv643xx_eth.c
> @@ -289,6 +289,7 @@ struct mv643xx_eth_shared_private {
> unsigned int t_clk;
> int extended_rx_coal_limit;
> int tx_bw_control;
> + int tx_csum_limit;
> };
>
> #define TX_BW_CONTROL_ABSENT 0
> @@ -782,7 +783,8 @@ static int txq_submit_skb(struct tx_queue *txq, struct sk_buff *skb)
> skb->protocol != htons(ETH_P_8021Q));
>
> tag_bytes = (void *)ip_hdr(skb) - (void *)skb->data - ETH_HLEN;
> - if (unlikely(tag_bytes & ~12)) {
> + if (unlikely(tag_bytes & ~12) ||
> + skb->len > mp->shared->tx_csum_limit) {

Please line up skb->len with unlikely() on the line above it.


> @@ -2666,6 +2668,9 @@ static int mv643xx_eth_shared_probe(struct platform_device *pdev)
> * Detect hardware parameters.
> */
> msp->t_clk = (pd != NULL && pd->t_clk != 0) ? pd->t_clk : 133000000;
> + msp->tx_csum_limit = pd->tx_csum_limit ? pd->tx_csum_limit : 9 * 1024;
> + /* add header count so we can compare against skb->len */
> + msp->tx_csum_limit += ETH_HLEN;
> infer_hw_params(msp);

Is the limit 9 * 1024 + 14 for the whole packet, or 9 * 1024 for the IP
part?

I.e. what happens if skb->len is 9 * 1024 + 15, but there is one VLAN
tag present -- will the hardware be able to do the checksum offload or
not?
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