Subject: Re: [PATCH net-next 6/8] net: phy: mscc: timestamping and PHC support

From: Richard Cochran <[email-masked]>
Date: Thu, 28 May 2020 07:34:40 -0700

On Wed, May 27, 2020 at 06:41:56PM +0200, Antoine Tenart wrote:

> +static struct vsc85xx_ptphdr *get_ptp_header(struct sk_buff *skb)
> +{
> +	struct ethhdr *ethhdr = eth_hdr(skb);
> +	struct iphdr *iphdr = ip_hdr(skb);
> +	struct udphdr *udphdr;
> +	__u8 proto;
> +
> +	if (ethhdr->h_proto == htons(ETH_P_1588))
> +		return (struct vsc85xx_ptphdr *)(((unsigned char *)ethhdr) +
> +					 skb_mac_header_len(skb));
> +
> +	if (ethhdr->h_proto != htons(ETH_P_IP))
> +		return NULL;
> +
> +	proto = iphdr->protocol;
> +	if (proto != IPPROTO_UDP)
> +		return NULL;
> +
> +	udphdr = udp_hdr(skb);
> +
> +	if (udphdr->source != ntohs(PTP_EV_PORT) ||
> +	    udphdr->dest != ntohs(PTP_EV_PORT))
> +		return NULL;
> +
> +	return (struct vsc85xx_ptphdr *)(((unsigned char *)udphdr) + UDP_HLEN);
> +}

This looks a lot like get_ptp_header_rx() below.  Are you sure you
need two almost identical methods?

> +static void vsc85xx_get_tx_ts(struct vsc85xx_ptp *ptp)
> +{
> +	struct skb_shared_hwtstamps shhwtstamps;
> +	struct sk_buff *skb, *first_skb = NULL;
> +	struct vsc85xx_ts_fifo fifo;
> +	u8 i, skb_sig[16], *p;
> +	unsigned long ns;
> +	s64 secs;
> +	u32 reg;
> +
> +next_in_fifo:
> +	memset(&fifo, 0, sizeof(fifo));
> +	p = (u8 *)&fifo;
> +
> +	reg = vsc85xx_ts_read_csr(ptp->phydev, PROCESSOR,
> +				  MSCC_PHY_PTP_EGR_TS_FIFO(0));
> +	if (reg & PTP_EGR_TS_FIFO_EMPTY)
> +		goto out;
> +
> +	*p++ = reg & 0xff;
> +	*p++ = (reg >> 8) & 0xff;
> +
> +	/* Reading FIFO6 pops the FIFO item */
> +	for (i = 1; i < 7; i++) {
> +		reg = vsc85xx_ts_read_csr(ptp->phydev, PROCESSOR,
> +					  MSCC_PHY_PTP_EGR_TS_FIFO(i));
> +		*p++ = reg & 0xff;
> +		*p++ = (reg >> 8) & 0xff;
> +		*p++ = (reg >> 16) & 0xff;
> +		*p++ = (reg >> 24) & 0xff;
> +	}
> +
> +next_in_queue:
> +	skb = skb_dequeue(&ptp->tx_queue);
> +	if (!skb || skb == first_skb)
> +		goto out;
> +
> +	/* Keep the first skb to avoid looping over it again. */
> +	if (!first_skb)
> +		first_skb = skb;
> +
> +	/* Can't get the signature of the packet, won't ever
> +	 * be able to have one so let's dequeue the packet.
> +	 */
> +	if (get_sig(skb, skb_sig) < 0)
> +		goto next_in_queue;
> +
> +	/* Valid signature but does not match the one of the
> +	 * packet in the FIFO right now, reschedule it for later
> +	 * packets.
> +	 */
> +	if (memcmp(skb_sig, fifo.sig, sizeof(fifo.sig))) {
> +		skb_queue_tail(&ptp->tx_queue, skb);
> +		goto next_in_queue;
> +	}
> +
> +	ns = fifo.ns;
> +	secs = fifo.secs;
> +
> +	memset(&shhwtstamps, 0, sizeof(shhwtstamps));
> +	shhwtstamps.hwtstamp = ktime_set(secs, ns);
> +	skb_complete_tx_timestamp(skb, &shhwtstamps);
> +
> +out:
> +	/* If other timestamps are available in the FIFO, process them. */
> +	reg = vsc85xx_ts_read_csr(ptp->phydev, PROCESSOR,
> +				  MSCC_PHY_PTP_EGR_TS_FIFO_CTRL);
> +	if (PTP_EGR_FIFO_LEVEL_LAST_READ(reg) > 1)
> +		goto next_in_fifo;
> +}

AFAICT, there is no need for labels and jumps here.  Two nested 'for'
loops will do nicely.  The inner skb loop can be in a helper function
for clarity.  Be sure to use the "safe" iterator over the skbs.

> +static void vsc85xx_txtstamp(struct mii_timestamper *mii_ts,
> +			     struct sk_buff *skb, int type)
> +{
> +	struct vsc8531_private *vsc8531 =
> +		container_of(mii_ts, struct vsc8531_private, mii_ts);
> +
> +	if (!skb || !vsc8531->ptp->configured)

The skb cannot be NULL here.  See net/core/timestamping.c

> +		return;
> +
> +	if (vsc8531->ptp->tx_type == HWTSTAMP_TX_OFF) {
> +		kfree_skb(skb);
> +		return;
> +	}
> +
> +	skb_shinfo(skb)->tx_flags |= SKBTX_IN_PROGRESS;
> +	skb_queue_tail(&vsc8531->ptp->tx_queue, skb);
> +	/* Scheduling the work for the TS FIFO is handled by the IRQ routine */
> +}
> +
> +static bool vsc85xx_rxtstamp(struct mii_timestamper *mii_ts,
> +			     struct sk_buff *skb, int type)
> +{
> +	struct vsc8531_private *vsc8531 =
> +		container_of(mii_ts, struct vsc8531_private, mii_ts);
> +	struct skb_shared_hwtstamps *shhwtstamps = NULL;
> +	struct vsc85xx_ptphdr *ptphdr;
> +	struct timespec64 ts;
> +	unsigned long ns;
> +
> +	if (!skb || !vsc8531->ptp->configured)

Again, skb can't be null.

Thanks,
Richard