Netdev Archive on lore.kernel.org
help / color / mirror / Atom feed
From: Richard Cochran <richardcochran@gmail.com>
To: Vladimir Oltean <olteanv@gmail.com>
Cc: Kurt Kanzenbach <kurt@linutronix.de>,
	Andrew Lunn <andrew@lunn.ch>,
	Vivien Didelot <vivien.didelot@gmail.com>,
	Florian Fainelli <f.fainelli@gmail.com>,
	"David S. Miller" <davem@davemloft.net>,
	Jakub Kicinski <kuba@kernel.org>,
	netdev@vger.kernel.org, Rob Herring <robh+dt@kernel.org>,
	devicetree@vger.kernel.org,
	Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
	Kamil Alkhouri <kamil.alkhouri@hs-offenburg.de>,
	ilias.apalodimas@linaro.org
Subject: Re: [PATCH v1 4/8] net: dsa: hellcreek: Add support for hardware timestamping
Date: Mon, 13 Jul 2020 08:38:31 -0700	[thread overview]
Message-ID: <20200713153831.GA29291@hoboy> (raw)
In-Reply-To: <20200713141217.ktgh5rtullmrjjsy@skbuf>

On Mon, Jul 13, 2020 at 05:12:17PM +0300, Vladimir Oltean wrote:
> On Mon, Jul 13, 2020 at 07:01:12AM -0700, Richard Cochran wrote:
> > I don't think it makes sense for DSA drivers to set this bit, as it
> > serves no purpose in the DSA context.
> > 
> 
> For whom does this bit serve a purpose, though, and how do you tell?

It had a historical purpose.  Originally, the stack delivered either a
hardware or a software time stamp, but not both.  This restriction was
eventually lifted via the SOF_TIMESTAMPING_OPT_TX_SWHW option, but
still the original behavior is preserved as the default.

You can see how SKBTX_IN_PROGRESS is used by the skb_tstamp_tx() path
here:

void __skb_tstamp_tx(struct sk_buff *orig_skb,
		     struct skb_shared_hwtstamps *hwtstamps,
		     struct sock *sk, int tstype)
{
	...

	if (!hwtstamps && !(sk->sk_tsflags & SOF_TIMESTAMPING_OPT_TX_SWHW) &&
	    skb_shinfo(orig_skb)->tx_flags & SKBTX_IN_PROGRESS)
		return;
}

It prevents SW time stamp when the flag is set.

Note that DSA drivers deliver TX time stamps via a different path,
namely skb_complete_tx_timestamp().  Also, DSA drivers don't provide
SW time stamping at all.

Q: When should drivers set SKBTX_IN_PROGRESS?

A: When the interface they represent offers both
   SOF_TIMESTAMPING_TX_HARDWARE and SOF_TIMESTAMPING_TX_SOFTWARE.

HTH,
Richard




  reply	other threads:[~2020-07-13 15:38 UTC|newest]

Thread overview: 31+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-10 11:36 [PATCH v1 0/8] Hirschmann Hellcreek DSA driver Kurt Kanzenbach
2020-07-10 11:36 ` [PATCH v1 1/8] net: dsa: Add tag handling for Hirschmann Hellcreek switches Kurt Kanzenbach
2020-07-12  2:57   ` Florian Fainelli
2020-07-10 11:36 ` [PATCH v1 2/8] net: dsa: Add DSA driver " Kurt Kanzenbach
2020-07-11 20:33   ` Florian Fainelli
2020-07-13  6:30     ` Kurt Kanzenbach
2020-07-16  8:29       ` Vladimir Oltean
2020-07-16  9:23         ` Kurt Kanzenbach
2020-07-16  9:39           ` Vladimir Oltean
2020-07-16 10:06             ` Kurt Kanzenbach
2020-07-10 11:36 ` [PATCH v1 3/8] net: dsa: hellcreek: Add PTP clock support Kurt Kanzenbach
2020-07-11 20:30   ` Richard Cochran
2020-07-11 20:38   ` Florian Fainelli
2020-07-13  6:34     ` Kurt Kanzenbach
2020-07-10 11:36 ` [PATCH v1 4/8] net: dsa: hellcreek: Add support for hardware timestamping Kurt Kanzenbach
2020-07-11 20:38   ` Richard Cochran
2020-07-13  6:35     ` Kurt Kanzenbach
2020-07-13  9:57   ` Vladimir Oltean
2020-07-13 10:57     ` Kurt Kanzenbach
2020-07-13 14:01       ` Richard Cochran
2020-07-13 14:12         ` Vladimir Oltean
2020-07-13 15:38           ` Richard Cochran [this message]
2020-07-10 11:36 ` [PATCH v1 5/8] net: dsa: hellcreek: Add TAPRIO offloading support Kurt Kanzenbach
2020-07-10 11:36 ` [PATCH v1 6/8] net: dsa: hellcreek: Add PTP status LEDs Kurt Kanzenbach
2020-07-10 11:36 ` [PATCH v1 7/8] dt-bindings: Add vendor prefix for Hirschmann Kurt Kanzenbach
2020-07-11 20:11   ` Florian Fainelli
2020-07-20 22:49   ` Rob Herring
2020-07-10 11:36 ` [PATCH v1 8/8] dt-bindings: net: dsa: Add documentation for Hellcreek switches Kurt Kanzenbach
2020-07-11 20:18   ` Florian Fainelli
2020-07-13  6:45     ` Kurt Kanzenbach
2020-07-13 14:44       ` Rob Herring

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20200713153831.GA29291@hoboy \
    --to=richardcochran@gmail.com \
    --cc=andrew@lunn.ch \
    --cc=bigeasy@linutronix.de \
    --cc=davem@davemloft.net \
    --cc=devicetree@vger.kernel.org \
    --cc=f.fainelli@gmail.com \
    --cc=ilias.apalodimas@linaro.org \
    --cc=kamil.alkhouri@hs-offenburg.de \
    --cc=kuba@kernel.org \
    --cc=kurt@linutronix.de \
    --cc=netdev@vger.kernel.org \
    --cc=olteanv@gmail.com \
    --cc=robh+dt@kernel.org \
    --cc=vivien.didelot@gmail.com \
    --subject='Re: [PATCH v1 4/8] net: dsa: hellcreek: Add support for hardware timestamping' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
on how to clone and mirror all data and code used for this inbox