netdev - Re: [PATCH v2 net-next 3/8] net: mvneta: rely on build_skb in mvneta_rx

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Date:   Thu, 10 Oct 2019 10:16:52 +0300
From:   Ilias Apalodimas <ilias.apalodimas@...aro.org>
To:     Lorenzo Bianconi <lorenzo@...nel.org>
Cc:     netdev@...r.kernel.org, lorenzo.bianconi@...hat.com,
        davem@...emloft.net, thomas.petazzoni@...tlin.com,
        brouer@...hat.com, matteo.croce@...hat.com, mw@...ihalf.com
Subject: Re: [PATCH v2 net-next 3/8] net: mvneta: rely on build_skb in
 mvneta_rx_swbm poll routine

Hi Lorenzo, 

On Thu, Oct 10, 2019 at 01:18:33AM +0200, Lorenzo Bianconi wrote:
> Refactor mvneta_rx_swbm code introducing mvneta_swbm_rx_frame and
> mvneta_swbm_add_rx_fragment routines. Rely on build_skb in oreder to
> allocate skb since the previous patch introduced buffer recycling using
> the page_pool API.
> This patch fixes even an issue in the original driver where dma buffers
> are accessed before dma sync
> 
> Signed-off-by: Ilias Apalodimas <ilias.apalodimas@...aro.org>
> Signed-off-by: Jesper Dangaard Brouer <brouer@...hat.com>
> Signed-off-by: Lorenzo Bianconi <lorenzo@...nel.org>
> ---
>  drivers/net/ethernet/marvell/mvneta.c | 198 ++++++++++++++------------
>  1 file changed, 104 insertions(+), 94 deletions(-)
> 
> diff --git a/drivers/net/ethernet/marvell/mvneta.c b/drivers/net/ethernet/marvell/mvneta.c
> index 31cecc1ed848..79a6bac0192b 100644
> --- a/drivers/net/ethernet/marvell/mvneta.c
> +++ b/drivers/net/ethernet/marvell/mvneta.c
> @@ -323,6 +323,11 @@
>  	      ETH_HLEN + ETH_FCS_LEN,			     \
>  	      cache_line_size())
>  
> +#define MVNETA_SKB_PAD	(SKB_DATA_ALIGN(sizeof(struct skb_shared_info) + \
> +			 NET_SKB_PAD))
> +#define MVNETA_SKB_SIZE(len)	(SKB_DATA_ALIGN(len) + MVNETA_SKB_PAD)
> +#define MVNETA_MAX_RX_BUF_SIZE	(PAGE_SIZE - MVNETA_SKB_PAD)
> +
>  #define IS_TSO_HEADER(txq, addr) \
>  	((addr >= txq->tso_hdrs_phys) && \
>  	 (addr < txq->tso_hdrs_phys + txq->size * TSO_HEADER_SIZE))
> @@ -646,7 +651,6 @@ static int txq_number = 8;
>  static int rxq_def;
>  
>  static int rx_copybreak __read_mostly = 256;
> -static int rx_header_size __read_mostly = 128;
>  
>  /* HW BM need that each port be identify by a unique ID */
>  static int global_port_id;
> +	if (rxq->left_size > MVNETA_MAX_RX_BUF_SIZE) {

[...]

> +		len = MVNETA_MAX_RX_BUF_SIZE;
> +		data_len = len;
> +	} else {
> +		len = rxq->left_size;
> +		data_len = len - ETH_FCS_LEN;
> +	}
> +	dma_dir = page_pool_get_dma_dir(rxq->page_pool);
> +	dma_sync_single_range_for_cpu(dev->dev.parent,
> +				      rx_desc->buf_phys_addr, 0,
> +				      len, dma_dir);
> +	if (data_len > 0) {
> +		/* refill descriptor with new buffer later */
> +		skb_add_rx_frag(rxq->skb,
> +				skb_shinfo(rxq->skb)->nr_frags,
> +				page, NET_SKB_PAD, data_len,
> +				PAGE_SIZE);
> +
> +		page_pool_release_page(rxq->page_pool, page);
> +		rx_desc->buf_phys_addr = 0;

Shouldn't we unmap and set the buf_phys_addr to 0 regardless of the data_len?

> +	}
> +	rxq->left_size -= len;
> +}
> +
>  		mvneta_rxq_buf_size_set(pp, rxq, PAGE_SIZE < SZ_64K ?

[...]

> -					PAGE_SIZE :
> +					MVNETA_MAX_RX_BUF_SIZE :
>  					MVNETA_RX_BUF_SIZE(pp->pkt_size));
>  		mvneta_rxq_bm_disable(pp, rxq);
>  		mvneta_rxq_fill(pp, rxq, rxq->size);
> @@ -4656,7 +4666,7 @@ static int mvneta_probe(struct platform_device *pdev)
>  	SET_NETDEV_DEV(dev, &pdev->dev);
>  
>  	pp->id = global_port_id++;
> -	pp->rx_offset_correction = 0; /* not relevant for SW BM */
> +	pp->rx_offset_correction = NET_SKB_PAD;
>  
>  	/* Obtain access to BM resources if enabled and already initialized */
>  	bm_node = of_parse_phandle(dn, "buffer-manager", 0);
> -- 
> 2.21.0
> 

Regards
/Ilias