[LEDE-DEV] [PATCH] ag71xx: Add some unlikely calls + rearange some stuff in hard_start_xmit.

[Rosen Penev]

On Tue, Feb 13, 2018 at 10:52 PM, John Crispin <john at phrozen.org> wrote:
>
>
> On 13/02/18 23:53, Rosen Penev wrote:
>>
>> Based on Qualcomm driver. Improves iperf3 throughput by ~20mbps on
>> transmit on Archer C7v4.
>
>
> this is missing the description of what the patch does.
Unfortunately I have no real idea as of yet.
>
>     John
>
>>
>> Signed-off-by: Rosen Penev <rosenp at gmail.com>
>> ---
>>   .../drivers/net/ethernet/atheros/ag71xx/ag71xx_main.c      | 14
>> +++++++-------
>>   1 file changed, 7 insertions(+), 7 deletions(-)
>>
>> diff --git
>> a/target/linux/ar71xx/files/drivers/net/ethernet/atheros/ag71xx/ag71xx_main.c
>> b/target/linux/ar71xx/files/drivers/net/ethernet/atheros/ag71xx/ag71xx_main.c
>> index 95682b7641..d32f220178 100644
>> ---
>> a/target/linux/ar71xx/files/drivers/net/ethernet/atheros/ag71xx/ag71xx_main.c
>> +++
>> b/target/linux/ar71xx/files/drivers/net/ethernet/atheros/ag71xx/ag71xx_main.c
>> @@ -797,11 +797,14 @@ static netdev_tx_t ag71xx_hard_start_xmit(struct
>> sk_buff *skb,
>>         if (ag71xx_has_ar8216(ag))
>>                 ag71xx_add_ar8216_header(ag, skb);
>>   -     if (skb->len <= 4) {
>> +       dma_cache_sync (NULL, skb->data, skb->len, DMA_TO_DEVICE);
>> +
>> +       if (unlikely(skb->len <= 4)) {
>>                 DBG("%s: packet len is too small\n", ag->dev->name);
>>                 goto err_drop;
>>         }
>>   +     netdev_sent_queue(dev, skb->len);
>>         dma_addr = dma_map_single(&dev->dev, skb->data, skb->len,
>>                                   DMA_TO_DEVICE);
>>   @@ -817,27 +820,24 @@ static netdev_tx_t ag71xx_hard_start_xmit(struct
>> sk_buff *skb,
>>         ring->buf[i].len = skb->len;
>>         ring->buf[i].skb = skb;
>>   -     netdev_sent_queue(dev, skb->len);
>> -
>>         skb_tx_timestamp(skb);
>>         desc->ctrl &= ~DESC_EMPTY;
>>         ring->curr += n;
>>   -     /* flush descriptor */
>> -       wmb();
>> -
>>         ring_min = 2;
>>         if (ring->desc_split)
>>             ring_min *= AG71XX_TX_RING_DS_PER_PKT;
>>   -     if (ring->curr - ring->dirty >= ring_size - ring_min) {
>> +       if (unlikely(ring->curr - ring->dirty >= ring_size - ring_min)) {
>>                 DBG("%s: tx queue full\n", dev->name);
>>                 netif_stop_queue(dev);
>>         }
>>         DBG("%s: packet injected into TX queue\n", ag->dev->name);
>>   +     /* flush descriptor */
>> +       wmb();
>>         /* enable TX engine */
>>         ag71xx_wr(ag, AG71XX_REG_TX_CTRL, TX_CTRL_TXE);
>>
>
>