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From: Richard Cochran <richardcochran@gmail.com>
To: Olivier Dautricourt <olivier.dautricourt@orolia.com>
Cc: Giuseppe Cavallaro <peppe.cavallaro@st.com>,
	Alexandre Torgue <alexandre.torgue@st.com>,
	Jose Abreu <joabreu@synopsys.com>,
	"David S . Miller" <davem@davemloft.net>,
	netdev@vger.kernel.org
Subject: Re: [PATCH 0/3] Patch series for a PTP Grandmaster use case using stmmac/gmac3 ptp clock
Date: Thu, 14 May 2020 17:37:06 -0700	[thread overview]
Message-ID: <20200515003706.GB18192@localhost> (raw)
In-Reply-To: <20200514150900.GA12924@orolia.com>

On Thu, May 14, 2020 at 05:09:01PM +0200, Olivier Dautricourt wrote:
>   My issue is that the default behavior of the stmmac driver is to
>   set the mac into fine mode which implies to continuously do frequency
>   adjustment, So if i'm not mistaken using the nullf servo will not address
>   that issue even if we are not doing explicit clock_adjtime syscalls.

Why not use the external time stamps from your GPS to do one of the
following?

A) Feed them into a user space PI controller and do frequency
   correction, or

B) Feed the offsets into the hardware PLL (if that is present) using
   the new PHC ADJ_OFFSET support (found in net-next).

I don't see a need for changing any kernel interfaces at all.  If you
think there is such a need, then you will have to make some kind of
argument or justification for it.

BTW, support for B has been implemented in linuxptp, and the patches
will appear soon.  We can also add it into the ts2phc program if you
like.

Thanks,
Richard

  reply	other threads:[~2020-05-15  0:37 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-05-14 10:28 [PATCH 0/3] Patch series for a PTP Grandmaster use case using stmmac/gmac3 ptp clock Olivier Dautricourt
2020-05-14 10:28 ` [PATCH 1/3] net: stmmac: gmac3: add auxiliary snapshot support Olivier Dautricourt
2020-05-14 10:28 ` [PATCH 2/3] net: uapi: Add HWTSTAMP_FLAGS_ADJ_FINE/ADJ_COARSE Olivier Dautricourt
2020-05-14 13:38   ` Richard Cochran
2020-05-14 15:20     ` Olivier Dautricourt
2020-05-15  0:29       ` Richard Cochran
2020-05-14 10:28 ` [PATCH 3/3] net: stmmac: Support coarse mode through ioctl Olivier Dautricourt
2020-05-27  3:55   ` Richard Cochran
2020-06-03 16:12     ` Olivier Dautricourt
2020-05-14 13:53 ` [PATCH 0/3] Patch series for a PTP Grandmaster use case using stmmac/gmac3 ptp clock Richard Cochran
2020-05-14 15:09   ` Olivier Dautricourt
2020-05-15  0:37     ` Richard Cochran [this message]
2020-05-15 13:26       ` Julien Beraud
2020-05-15 23:30         ` Richard Cochran
2020-05-25 10:00           ` Olivier Dautricourt
2020-05-27  4:05         ` Richard Cochran
2020-06-03 15:17           ` Olivier Dautricourt

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