Subject: Re: [PATCH v2 2/2] net: hisilicon: add hix5hd2 mac driver

From: Mark Rutland <[email-masked]>
Date: Tue, 27 May 2014 14:57:27 +0100

On Tue, May 27, 2014 at 01:44:27PM +0100, Zhangfei Gao wrote:
> Add support for the hix5hd2 XGMAC 1Gb ethernet device.
> The controller requires two queues for tx and two queues for rx.
> Controller fetch buffer from free queue and then push to used queue.
> Diver should prepare free queue and free buffer from used queue.
> 
> Signed-off-by: Zhangfei Gao <[email-masked]>
> ---
>  drivers/net/ethernet/Kconfig                  |    1 +
>  drivers/net/ethernet/Makefile                 |    1 +
>  drivers/net/ethernet/hisilicon/Kconfig        |   27 +
>  drivers/net/ethernet/hisilicon/Makefile       |    5 +
>  drivers/net/ethernet/hisilicon/hix5hd2_gmac.c | 1057 +++++++++++++++++++++++++
>  5 files changed, 1091 insertions(+)
>  create mode 100644 drivers/net/ethernet/hisilicon/Kconfig
>  create mode 100644 drivers/net/ethernet/hisilicon/Makefile
>  create mode 100644 drivers/net/ethernet/hisilicon/hix5hd2_gmac.c

[...]

> +struct hix5hd2_desc {
> +       __le32 buff_addr;
> +       __le32 cmd;
> +} __aligned(32);

[...]

> +static void hix5hd2_rx_refill(struct hix5hd2_priv *priv)
> +{
> +       struct hix5hd2_desc *desc;
> +       struct sk_buff *skb;
> +       u32 start, end, num, pos, i;
> +
> +       /* software write pointer */
> +       start = dma_cnt(readl_relaxed(priv->base + RX_FQ_WR_ADDR));
> +       /* logic read pointer */
> +       end = dma_cnt(readl_relaxed(priv->base + RX_FQ_RD_ADDR));
> +       num = CIRC_SPACE(start, end, RX_DESC_NUM);
> +
> +       for (i = 0, pos = start; i < num; i++) {
> +               if (priv->rx_skb[pos])
> +                       break;
> +               else {
> +                       skb = netdev_alloc_skb_ip_align(priv->netdev,
> +                               MAC_MAX_FRAME_SIZE);
> +                       if (unlikely(skb == NULL))
> +                               break;
> +               }
> +
> +               desc = priv->rx_fq.desc + pos;
> +               desc->buff_addr =
> +                       dma_map_single(priv->dev, skb->data,
> +                                       MAC_MAX_FRAME_SIZE, DMA_FROM_DEVICE);

buff_addr was declared as an __le32, but here we're pasting values of
the kernel's native endianness (which might not be little). You will
need to carefully convert the endianness of this value when dealing with
it.

> +               if (dma_mapping_error(priv->dev, desc->buff_addr)) {
> +                       dev_kfree_skb_any(skb);
> +                       break;
> +               }
> +
> +               priv->rx_skb[pos] = skb;
> +               desc->cmd = (MAC_MAX_FRAME_SIZE - 1) | DESC_VLD_FREE;

Likewise cmd was described as an __le32 and needs to be converted
appropriately.

Cheers,
Mark.