On Wed, 16 Oct 2019 23:03:08 +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.
> mvneta driver can run on not cache coherent devices so it is
> necessary to sync DMA buffers before sending them to the device
> in order to avoid memory corruptions. Running perf analysis we can
> see a performance cost associated with this DMA-sync (anyway it is
> already there in the original driver code). In follow up patches we
> will add more logic to reduce DMA-sync as much as possible.
> 
> Signed-off-by: Ilias Apalodimas <ilias.apalodi...@linaro.org>
> Signed-off-by: Jesper Dangaard Brouer <bro...@redhat.com>
> Signed-off-by: Lorenzo Bianconi <lore...@kernel.org>
> ---
>  drivers/net/ethernet/marvell/mvneta.c | 201 ++++++++++++++------------
>  1 file changed, 107 insertions(+), 94 deletions(-)
> 
> diff --git a/drivers/net/ethernet/marvell/mvneta.c 
> b/drivers/net/ethernet/marvell/mvneta.c
> index 9e4d828787fd..2f8123224f6e 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;
> @@ -1817,6 +1821,7 @@ static int mvneta_rx_refill(struct mvneta_port *pp,
>                           struct mvneta_rx_queue *rxq,
>                           gfp_t gfp_mask)
>  {
> +     enum dma_data_direction dma_dir;
>       dma_addr_t phys_addr;
>       struct page *page;
>  
> @@ -1826,6 +1831,9 @@ static int mvneta_rx_refill(struct mvneta_port *pp,
>               return -ENOMEM;
>  
>       phys_addr = page_pool_get_dma_addr(page) + pp->rx_offset_correction;
> +     dma_dir = page_pool_get_dma_dir(rxq->page_pool);
> +     dma_sync_single_for_device(pp->dev->dev.parent, phys_addr,
> +                                MVNETA_MAX_RX_BUF_SIZE, dma_dir);

This belongs in patch 2.

>       mvneta_rx_desc_fill(rx_desc, phys_addr, page, rxq);
>  
>       return 0;
> @@ -1942,30 +1950,101 @@ int mvneta_rx_refill_queue(struct mvneta_port *pp, 
> struct mvneta_rx_queue *rxq)
>       return i;
>  }

>  /* Main rx processing when using software buffer management */
>  static int mvneta_rx_swbm(struct napi_struct *napi,
>                         struct mvneta_port *pp, int budget,
>                         struct mvneta_rx_queue *rxq)
>  {
> -     struct net_device *dev = pp->dev;
> -     int rx_todo, rx_proc;
> -     int refill = 0;
> -     u32 rcvd_pkts = 0;
> -     u32 rcvd_bytes = 0;
> +     int rcvd_pkts = 0, rcvd_bytes = 0;
> +     int rx_pending, refill, done = 0;
>  
>       /* Get number of received packets */
> -     rx_todo = mvneta_rxq_busy_desc_num_get(pp, rxq);
> -     rx_proc = 0;
> +     rx_pending = mvneta_rxq_busy_desc_num_get(pp, rxq);
>  
>       /* Fairness NAPI loop */
> -     while ((rcvd_pkts < budget) && (rx_proc < rx_todo)) {
> +     while (done < budget && done < rx_pending) {
>               struct mvneta_rx_desc *rx_desc = mvneta_rxq_next_desc_get(rxq);
>               unsigned char *data;
>               struct page *page;
> -             dma_addr_t phys_addr;
> -             u32 rx_status, index;
> -             int rx_bytes, skb_size, copy_size;
> -             int frag_num, frag_size, frag_offset;
> +             int index;
>  
>               index = rx_desc - rxq->descs;
>               page = (struct page *)rxq->buf_virt_addr[index];
> @@ -1973,98 +2052,33 @@ static int mvneta_rx_swbm(struct napi_struct *napi,
>               /* Prefetch header */
>               prefetch(data);
>  
> -             phys_addr = rx_desc->buf_phys_addr;
> -             rx_status = rx_desc->status;
> -             rx_proc++;
>               rxq->refill_num++;
> +             done++;
> +
> +             if (rx_desc->status & MVNETA_RXD_FIRST_DESC) {
> +                     int err;
>  
> -             if (rx_status & MVNETA_RXD_FIRST_DESC) {

If I may nit pick - not removing the rx_status and dev local variables
could make this chunk a little bit more readable - could you experiment
in moving that to a separate patch?

>                       /* Check errors only for FIRST descriptor */
> -                     if (rx_status & MVNETA_RXD_ERR_SUMMARY) {
> +                     if (rx_desc->status & MVNETA_RXD_ERR_SUMMARY) {
>                               mvneta_rx_error(pp, rx_desc);
> -                             dev->stats.rx_errors++;
> +                             pp->dev->stats.rx_errors++;
>                               /* leave the descriptor untouched */
>                               continue;
>                       }
> -                     rx_bytes = rx_desc->data_size -
> -                                (ETH_FCS_LEN + MVNETA_MH_SIZE);
>  
> -                     /* Allocate small skb for each new packet */
> -                     skb_size = max(rx_copybreak, rx_header_size);
> -                     rxq->skb = netdev_alloc_skb_ip_align(dev, skb_size);
> -                     if (unlikely(!rxq->skb)) {
> -                             netdev_err(dev,
> -                                        "Can't allocate skb on queue %d\n",
> -                                        rxq->id);
> -                             dev->stats.rx_dropped++;
> -                             rxq->skb_alloc_err++;
> +                     err = mvneta_swbm_rx_frame(pp, rx_desc, rxq, page);
> +                     if (err)
>                               continue;
> -                     }
> -                     copy_size = min(skb_size, rx_bytes);
> -
> -                     /* Copy data from buffer to SKB, skip Marvell header */
> -                     memcpy(rxq->skb->data, data + MVNETA_MH_SIZE,
> -                            copy_size);
> -                     skb_put(rxq->skb, copy_size);
> -                     rxq->left_size = rx_bytes - copy_size;
> -
> -                     mvneta_rx_csum(pp, rx_status, rxq->skb);
> -                     if (rxq->left_size == 0) {
> -                             int size = copy_size + MVNETA_MH_SIZE;
> -
> -                             dma_sync_single_range_for_cpu(dev->dev.parent,
> -                                                           phys_addr, 0,
> -                                                           size,
> -                                                           DMA_FROM_DEVICE);
> -
> -                             /* leave the descriptor and buffer untouched */
> -                     } else {
> -                             /* refill descriptor with new buffer later */
> -                             rx_desc->buf_phys_addr = 0;
> -
> -                             frag_num = 0;
> -                             frag_offset = copy_size + MVNETA_MH_SIZE;
> -                             frag_size = min(rxq->left_size,
> -                                             (int)(PAGE_SIZE - frag_offset));
> -                             skb_add_rx_frag(rxq->skb, frag_num, page,
> -                                             frag_offset, frag_size,
> -                                             PAGE_SIZE);
> -                             page_pool_release_page(rxq->page_pool, page);
> -                             rxq->left_size -= frag_size;
> -                     }
>               } else {
> -                     /* Middle or Last descriptor */
>                       if (unlikely(!rxq->skb)) {
>                               pr_debug("no skb for rx_status 0x%x\n",
> -                                      rx_status);
> +                                      rx_desc->status);
>                               continue;
>                       }
> -                     if (!rxq->left_size) {
> -                             /* last descriptor has only FCS */
> -                             /* and can be discarded */
> -                             dma_sync_single_range_for_cpu(dev->dev.parent,
> -                                                           phys_addr, 0,
> -                                                           ETH_FCS_LEN,
> -                                                           DMA_FROM_DEVICE);
> -                             /* leave the descriptor and buffer untouched */
> -                     } else {
> -                             /* refill descriptor with new buffer later */
> -                             rx_desc->buf_phys_addr = 0;
> -
> -                             frag_num = skb_shinfo(rxq->skb)->nr_frags;
> -                             frag_offset = 0;
> -                             frag_size = min(rxq->left_size,
> -                                             (int)(PAGE_SIZE - frag_offset));
> -                             skb_add_rx_frag(rxq->skb, frag_num, page,
> -                                             frag_offset, frag_size,
> -                                             PAGE_SIZE);
> -
> -                             page_pool_release_page(rxq->page_pool, page);
> -                             rxq->left_size -= frag_size;
> -                     }
> +                     mvneta_swbm_add_rx_fragment(pp, rx_desc, rxq, page);
>               } /* Middle or Last descriptor */
>  
> -             if (!(rx_status & MVNETA_RXD_LAST_DESC))
> +             if (!(rx_desc->status & MVNETA_RXD_LAST_DESC))
>                       /* no last descriptor this time */
>                       continue;
>  
> @@ -2080,13 +2094,12 @@ static int mvneta_rx_swbm(struct napi_struct *napi,
>               rcvd_bytes += rxq->skb->len;
>  
>               /* Linux processing */
> -             rxq->skb->protocol = eth_type_trans(rxq->skb, dev);
> +             rxq->skb->protocol = eth_type_trans(rxq->skb, pp->dev);
>  
>               napi_gro_receive(napi, rxq->skb);
>  
>               /* clean uncomplete skb pointer in queue */
>               rxq->skb = NULL;
> -             rxq->left_size = 0;
>       }
>  
>       mvneta_update_stats(pp, rcvd_pkts, rcvd_bytes, false);

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