[net-next,v5,2/2] net: ethernet: mediatek: enhance RX path by aggregating more SKBs into NAPI

From: Sean Wang <sean.wang@mediatek.com>

The patch adds support for aggregating more SKBs feed into NAPI in
order to get more benefits from generic receive offload (GRO) by
peeking at the RX ring status and moving more packets right before
returning from NAPI RX polling handler if NAPI budgets are still
available and some packets already present in hardware.

Signed-off-by: Sean Wang <sean.wang@mediatek.com>
---
 drivers/net/ethernet/mediatek/mtk_eth_soc.c | 31 ++++++++++++++++-------------
 1 file changed, 17 insertions(+), 14 deletions(-)

On 03/09/2016 11:59, sean.wang@mediatek.com wrote:
> From: Sean Wang <sean.wang@mediatek.com>
> 
> The patch adds support for aggregating more SKBs feed into NAPI in
> order to get more benefits from generic receive offload (GRO) by
> peeking at the RX ring status and moving more packets right before
> returning from NAPI RX polling handler if NAPI budgets are still
> available and some packets already present in hardware.
> 
> Signed-off-by: Sean Wang <sean.wang@mediatek.com>

this looks ok to me, gave it a quick try on my HW and it works well. i
am just not sure if this is something that is commonly done. someone
with more overview of how NAPI should be used might want to comment on this.

Tested-by: John Crispin <john@phrozen.org>


> ---
>  drivers/net/ethernet/mediatek/mtk_eth_soc.c | 31 ++++++++++++++++-------------
>  1 file changed, 17 insertions(+), 14 deletions(-)
> 
> diff --git a/drivers/net/ethernet/mediatek/mtk_eth_soc.c b/drivers/net/ethernet/mediatek/mtk_eth_soc.c
> index a1bdb53..66fd45a 100644
> --- a/drivers/net/ethernet/mediatek/mtk_eth_soc.c
> +++ b/drivers/net/ethernet/mediatek/mtk_eth_soc.c
> @@ -893,14 +893,14 @@ release_desc:
>  
>  		done++;
>  	}
> -	/* make sure that all changes to the dma ring are flushed before
> -	 * we continue
> -	 */
> -	wmb();
> -	mtk_w32(eth, ring->calc_idx, MTK_PRX_CRX_IDX0);
>  
> -	if (done < budget)
> -		mtk_w32(eth, MTK_RX_DONE_INT, MTK_PDMA_INT_STATUS);
> +	if (done) {
> +		/* make sure that all changes to the dma ring are flushed before
> +		 * we continue
> +		 */
> +		wmb();
> +		mtk_w32(eth, ring->calc_idx, MTK_PRX_CRX_IDX0);
> +	}
>  
>  	return done;
>  }
> @@ -1020,10 +1020,13 @@ static int mtk_napi_rx(struct napi_struct *napi, int budget)
>  	struct mtk_eth *eth = container_of(napi, struct mtk_eth, rx_napi);
>  	u32 status, mask;
>  	int rx_done = 0;
> +	int remain_budget = budget;
>  
>  	mtk_handle_status_irq(eth);
> +
> +poll_again:
>  	mtk_w32(eth, MTK_RX_DONE_INT, MTK_PDMA_INT_STATUS);
> -	rx_done = mtk_poll_rx(napi, budget, eth);
> +	rx_done = mtk_poll_rx(napi, remain_budget, eth);
>  
>  	if (unlikely(netif_msg_intr(eth))) {
>  		status = mtk_r32(eth, MTK_PDMA_INT_STATUS);
> @@ -1032,18 +1035,18 @@ static int mtk_napi_rx(struct napi_struct *napi, int budget)
>  			 "done rx %d, intr 0x%08x/0x%x\n",
>  			 rx_done, status, mask);
>  	}
> -
> -	if (rx_done == budget)
> +	if (rx_done == remain_budget)
>  		return budget;
>  
>  	status = mtk_r32(eth, MTK_PDMA_INT_STATUS);
> -	if (status & MTK_RX_DONE_INT)
> -		return budget;
> -
> +	if (status & MTK_RX_DONE_INT) {
> +		remain_budget -= rx_done;
> +		goto poll_again;
> +	}
>  	napi_complete(napi);
>  	mtk_irq_enable(eth, MTK_PDMA_INT_MASK, MTK_RX_DONE_INT);
>  
> -	return rx_done;
> +	return rx_done + budget - remain_budget;
>  }
>  
>  static int mtk_tx_alloc(struct mtk_eth *eth)
>