Subject: Re: [PATCH 3/3] gianfar: fix endianness for hardware timestamp

From: Richard Cochran <[email-masked]>
Date: Mon, 22 Feb 2016 09:48:03 +0100

On Mon, Feb 22, 2016 at 02:49:33PM +0800, Yangbo Lu wrote:
> @@ -2708,6 +2708,7 @@ static void gfar_clean_tx_ring(struct gfar_priv_tx_q *tx_queue)
>  			struct skb_shared_hwtstamps shhwtstamps;
>  			u64 *ns = (u64 *)(((uintptr_t)skb->data + 0x10) &
>  					  ~0x7UL);
> +			*ns = be64_to_cpu(*ns);
>  
>  			memset(&shhwtstamps, 0, sizeof(shhwtstamps));
>  			shhwtstamps.hwtstamp = ns_to_ktime(*ns);

There is no point in modifying the buffer data in place.

Instead, do this:

			memset(&shhwtstamps, 0, sizeof(shhwtstamps));
			shhwtstamps.hwtstamp = ns_to_ktime(be64_to_cpu(*ns));

or this:

			u64 ns, *ptr = (u64 *)(((uintptr_t)skb->data + 0x10) &
					       ~0x7UL);
			ns = be64_to_cpu(*ptr);

			memset(&shhwtstamps, 0, sizeof(shhwtstamps));
			shhwtstamps.hwtstamp = ns_to_ktime(ns);

> @@ -3037,6 +3038,7 @@ static void gfar_process_frame(struct net_device *ndev, struct sk_buff *skb)
>  	if (priv->hwts_rx_en) {
>  		struct skb_shared_hwtstamps *shhwtstamps = skb_hwtstamps(skb);
>  		u64 *ns = (u64 *) skb->data;
> +		*ns = be64_to_cpu(*ns);
>  
>  		memset(shhwtstamps, 0, sizeof(*shhwtstamps));
>  		shhwtstamps->hwtstamp = ns_to_ktime(*ns);

Same here.

Thanks,
Richard