On 10/17/2018 12:53 PM, Christian Lamparter wrote:
> This patch enables TSO(v4) hw feature for emac driver.
> As atleast the APM82181's TCP/IP acceleration hardware
> controller (TAH) provides TCP segmentation support in
> the transmit path.
>
> Signed-off-by: Christian Lamparter <chunk...@gmail.com>
> ---
> drivers/net/ethernet/ibm/emac/core.c | 101 ++++++++++++++++++++++++++-
> drivers/net/ethernet/ibm/emac/core.h | 4 ++
> drivers/net/ethernet/ibm/emac/emac.h | 7 ++
> drivers/net/ethernet/ibm/emac/tah.c | 20 ++++++
> drivers/net/ethernet/ibm/emac/tah.h | 2 +
> 5 files changed, 133 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/net/ethernet/ibm/emac/core.c
> b/drivers/net/ethernet/ibm/emac/core.c
> index be560f9031f4..49ffbd6e1707 100644
> --- a/drivers/net/ethernet/ibm/emac/core.c
> +++ b/drivers/net/ethernet/ibm/emac/core.c
> @@ -38,6 +38,9 @@
> #include <linux/mii.h>
> #include <linux/bitops.h>
> #include <linux/if_vlan.h>
> +#include <linux/ip.h>
> +#include <linux/ipv6.h>
> +#include <linux/tcp.h>
> #include <linux/workqueue.h>
> #include <linux/of.h>
> #include <linux/of_address.h>
> @@ -1410,6 +1413,52 @@ static inline u16 emac_tx_csum(struct emac_instance
> *dev,
> return 0;
> }
>
> +const u32 tah_ss[TAH_NO_SSR] = { 9000, 4500, 1500, 1300, 576, 176 };
> +
> +static int emac_tx_tso(struct emac_instance *dev, struct sk_buff *skb,
> + u16 *ctrl)
> +{
> + if (emac_has_feature(dev, EMAC_FTR_TAH_HAS_TSO) &&
> + skb_is_gso(skb) && !!(skb_shinfo(skb)->gso_type &
> + (SKB_GSO_TCPV4 | SKB_GSO_TCPV6))) {
> + u32 seg_size = 0, i;
> +
> + /* Get the MTU */
> + seg_size = skb_shinfo(skb)->gso_size + tcp_hdrlen(skb)
> + + skb_network_header_len(skb);
> +
> + /* Restriction applied for the segmentation size
> + * to use HW segmentation offload feature: the size
> + * of the segment must not be less than 168 bytes for
> + * DIX formatted segments, or 176 bytes for
> + * IEEE formatted segments.
> + *
> + * I use value 176 to check for the segment size here
> + * as it can cover both 2 conditions above.
> + */
> + if (seg_size < 176)
> + return -ENODEV;
> +
> + /* Get the best suitable MTU */
> + for (i = 0; i < ARRAY_SIZE(tah_ss); i++) {
> + u32 curr_seg = tah_ss[i];
> +
> + if (curr_seg > dev->ndev->mtu ||
> + curr_seg > seg_size)
> + continue;
> +
> + *ctrl &= ~EMAC_TX_CTRL_TAH_CSUM;
> + *ctrl |= EMAC_TX_CTRL_TAH_SSR(i);
> + return 0;
This is something that you can possibly take out of your hot path and
recalculate when the MTU actually changes?
[snip]
> +static netdev_tx_t emac_sw_tso(struct sk_buff *skb, struct net_device *ndev)
> +{
> + struct emac_instance *dev = netdev_priv(ndev);
> + struct sk_buff *segs, *curr;
> +
> + segs = skb_gso_segment(skb, ndev->features &
> + ~(NETIF_F_TSO | NETIF_F_TSO6));
> + if (IS_ERR_OR_NULL(segs)) {
> + goto drop;
> + } else {
> + while (segs) {
> + /* check for overflow */
> + if (dev->tx_cnt >= NUM_TX_BUFF) {
> + dev_kfree_skb_any(segs);
> + goto drop;
> + }
Would setting dev->max_gso_segs somehow help make sure the stack does
not feed you oversized GSO'd skbs?
--
Florian
