RE: [PATCH 09/10] dpaa_eth: add support for hardware timestamping

[Y.b. Lu]

Hi Richard,

> -----Original Message-----
> From: Richard Cochran [mailto:richardcochran@xxxxxxxxx]
> Sent: Monday, June 4, 2018 9:49 PM
> To: Y.b. Lu <yangbo.lu@xxxxxxx>
> Cc: netdev@xxxxxxxxxxxxxxx; Madalin-cristian Bucur
> <madalin.bucur@xxxxxxx>; Rob Herring <robh+dt@xxxxxxxxxx>; Shawn Guo
> <shawnguo@xxxxxxxxxx>; David S . Miller <davem@xxxxxxxxxxxxx>;
> devicetree@xxxxxxxxxxxxxxx; linuxppc-dev@xxxxxxxxxxxxxxxx;
> linux-arm-kernel@xxxxxxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx
> Subject: Re: [PATCH 09/10] dpaa_eth: add support for hardware timestamping
> 
> On Mon, Jun 04, 2018 at 03:08:36PM +0800, Yangbo Lu wrote:
> 
> > +if FSL_DPAA_ETH
> > +config FSL_DPAA_ETH_TS
> > +	bool "DPAA hardware timestamping support"
> > +	select PTP_1588_CLOCK_QORIQ
> > +	default n
> > +	help
> > +	  Enable DPAA hardware timestamping support.
> > +	  This option is useful for applications to get
> > +	  hardware time stamps on the Ethernet packets
> > +	  using the SO_TIMESTAMPING API.
> > +endif
> 
> You should drop this #ifdef.  In general, if a MAC supports time stamping and
> PHC, then the driver support should simply be compiled in.
> 
> [ When time stamping incurs a large run time performance penalty to
>   non-PTP users, then it might make sense to have a Kconfig option to
>   disable it, but that doesn't appear to be the case here. ]

[Y.b. Lu] Actually these timestamping codes affected DPAA networking performance in our previous performance test.
That's why we used ifdef for it.

> 
> > @@ -1615,6 +1635,24 @@ static int dpaa_eth_refill_bpools(struct
> dpaa_priv *priv)
> >  	skbh = (struct sk_buff **)phys_to_virt(addr);
> >  	skb = *skbh;
> >
> > +#ifdef CONFIG_FSL_DPAA_ETH_TS
> > +	if (priv->tx_tstamp &&
> > +	    skb_shinfo(skb)->tx_flags & SKBTX_HW_TSTAMP) {
> 
> This condition fits on one line easily.

[Y.b. Lu] Right. I will use one line in next version.

> 
> > +		struct skb_shared_hwtstamps shhwtstamps;
> > +		u64 ns;
> 
> Local variables belong at the top of the function.

[Y.b. Lu] Ok, will move them to the top in next verison.

> 
> > +		memset(&shhwtstamps, 0, sizeof(shhwtstamps));
> > +
> > +		if (!dpaa_get_tstamp_ns(priv->net_dev, &ns,
> > +					priv->mac_dev->port[TX],
> > +					(void *)skbh)) {
> > +			shhwtstamps.hwtstamp = ns_to_ktime(ns);
> > +			skb_tstamp_tx(skb, &shhwtstamps);
> > +		} else {
> > +			dev_warn(dev, "dpaa_get_tstamp_ns failed!\n");
> > +		}
> > +	}
> > +#endif
> >  	if (unlikely(qm_fd_get_format(fd) == qm_fd_sg)) {
> >  		nr_frags = skb_shinfo(skb)->nr_frags;
> >  		dma_unmap_single(dev, addr, qm_fd_get_offset(fd) + @@ -2086,6
> > +2124,14 @@ static int dpaa_start_xmit(struct sk_buff *skb, struct
> net_device *net_dev)
> >  	if (unlikely(err < 0))
> >  		goto skb_to_fd_failed;
> >
> > +#ifdef CONFIG_FSL_DPAA_ETH_TS
> > +	if (priv->tx_tstamp &&
> > +	    skb_shinfo(skb)->tx_flags & SKBTX_HW_TSTAMP) {
> 
> One line please.

[Y.b. Lu] No problem.

> 
> > +		fd.cmd |= FM_FD_CMD_UPD;
> > +		skb_shinfo(skb)->tx_flags |= SKBTX_IN_PROGRESS;
> > +	}
> > +#endif
> > +
> >  	if (likely(dpaa_xmit(priv, percpu_stats, queue_mapping, &fd) == 0))
> >  		return NETDEV_TX_OK;
> >
> 
> Thanks,
> Richard