netdev - Re: [PATCH 4/5] net: ethernet: mediatek: enable rx path by reducing memory barrier

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Message-ID: <2b336217-2711-a716-78be-4df51591761e@cogentembedded.com>
Date:	Mon, 15 Aug 2016 22:06:30 +0300
From:	Sergei Shtylyov <sergei.shtylyov@...entembedded.com>
To:	Sean Wang <sean.wang@...iatek.com>, john@...ozen.org,
	davem@...emloft.net
Cc:	nbd@...nwrt.org, netdev@...r.kernel.org,
	linux-mediatek@...ts.infradead.org, keyhaede@...il.com
Subject: Re: [PATCH 4/5] net: ethernet: mediatek: enable rx path by reducing
 memory barrier

Hello.

On 08/15/2016 06:03 PM, Sean Wang wrote:

> The patch makes moving wmb() to outside the loop that could help
> rx path handling more faster although that rx descriptors aren't

    RX.

> freed for DMA to use as soon as possible, but based on my experiment
> and the result show it still can reach about 943Mbpis tested on the

    Shows.

> setup with one port using gigaphy and 256 rx descriptors for

    RX.

> DMA to move.
>
> Signed-off-by: Sean Wang <sean.wang@...iatek.com>
> ---
>  drivers/net/ethernet/mediatek/mtk_eth_soc.c |   11 ++++++-----
>  1 file changed, 6 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/net/ethernet/mediatek/mtk_eth_soc.c b/drivers/net/ethernet/mediatek/mtk_eth_soc.c
> index b782330..53e24c1 100644
> --- a/drivers/net/ethernet/mediatek/mtk_eth_soc.c
> +++ b/drivers/net/ethernet/mediatek/mtk_eth_soc.c
> @@ -893,14 +893,15 @@ release_desc:
>  		rxd->rxd2 = RX_DMA_PLEN0(ring->buf_size);
>
>  		ring->calc_idx = idx;
> -		/* make sure that all changes to the dma ring are flushed before
> -		 * we continue
> -		 */
> -		wmb();
> -		mtk_w32(eth, ring->calc_idx, MTK_QRX_CRX_IDX0);
>  		done++;
>  	}
>
> +    /* make sure that all changes to the dma ring are flushed before
> +     * we continue
> +     */

    Please indent the comment with a tab, like the code after it.

> +	wmb();
> +	mtk_w32(eth, ring->calc_idx, MTK_QRX_CRX_IDX0);
> +
>  	if (done < budget)
>  		mtk_w32(eth, MTK_RX_DONE_INT, MTK_QMTK_INT_STATUS);
>

MBR, Sergei