Re: [PATCH 3/3] net: hisilicon: add hix5hd2 mac driver

Hi Arnd,

Thanks for the kind suggestions.

On 05/26/2014 10:51 PM, Arnd Bergmann wrote:

On Monday 19 May 2014, Zhangfei Gao wrote:

I only noticed one real issue with the driver:

quoted

+struct hix5hd2_desc {
+	__le32 buff_addr;
+	__le32 buff_len:11;
+	__le32 reserve2:5;
+	__le32 data_len:11;
+	__le32 reserve1:2;
+	__le32 fl:2;
+	__le32 descvid:1;
+} __aligned(32);
+

You should generall not use bitfields in hardware data structures, as that is
not endian safe and will prevent running a big-endian kernel on this machine.
Better convert this to a set of __le32 fields and explicit shifts and masks.

Got it, will update.

More knowledge about big-endian kernel is appreciated, in which case we 
should consider such kernel.
Can we only consider this driver is only running on arm, which is 
little-endian.

Two smaller things you should think about, I'm not entirely sure about these:

quoted

+static int hix5hd2_rx(struct net_device *dev, int limit)
+{
+	struct hix5hd2_priv *priv = netdev_priv(dev);
+	struct sk_buff *skb;
+	struct hix5hd2_desc *desc;
+	dma_addr_t dma_addr;
+	u32 start, end, num, pos, i, len;
+
+	/* software read pointer */
+	start = dma_cnt(readl_relaxed(priv->base + RX_BQ_RD_ADDR));
+	/* logic write pointer */
+	end = dma_cnt(readl_relaxed(priv->base + RX_BQ_WR_ADDR));

I think one of these needs to be readl() instead of readl_relaxed(),
to ensure the data is correctly ordered with regard to the pointer
access.

readl_relaxed can ensure the sequence.

quoted

+	if (pos != start)
+		writel(dma_byte(pos), priv->base + TX_RQ_RD_ADDR);

While this looks like it could be writel_relaxed().

En, I think all three cases can use xxx_relaxed.
These accesses are just update pointer used by internal logic and get 
pointer updated by internal logic.

Thanks

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