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From: Grygorii Strashko <grygorii.strashko@ti.com>
To: Richard Cochran <richardcochran@gmail.com>
Cc: Murali Karicheri <m-karicheri2@ti.com>,
	Wingman Kwok <w-kwok2@ti.com>,
	"David S. Miller" <davem@davemloft.net>, <netdev@vger.kernel.org>,
	Mugunthan V N <mugunthanvnm@ti.com>, Sekhar Nori <nsekhar@ti.com>,
	<linux-kernel@vger.kernel.org>, <linux-omap@vger.kernel.org>,
	Rob Herring <robh+dt@kernel.org>, <devicetree@vger.kernel.org>
Subject: Re: [PATCH 4/6] net: ethernet: ti: cpts: add ptp pps support
Date: Fri, 2 Dec 2016 11:58:34 -0600	[thread overview]
Message-ID: <bfbebf2d-d057-6a21-845c-48f0a9ab0404@ti.com> (raw)
In-Reply-To: <20161202095848.GA14586@localhost.localdomain>

Hi Richard,

On 12/02/2016 03:58 AM, Richard Cochran wrote:
> On Wed, Nov 30, 2016 at 11:17:38PM +0100, Richard Cochran wrote:
>> On Wed, Nov 30, 2016 at 02:43:57PM -0600, Grygorii Strashko wrote:
>>> Sry, but this is questionable - code for pps comes from TI internal
>>> branches (SDK releases) where it survived for a pretty long time.
> 
> Actually, there is a way to get an accurate PPS from the am335x.  See
> this recent thread:
> 
>    https://www.mail-archive.com/linuxptp-devel@lists.sourceforge.net/msg01726.html
> 
> That is the way to go, and so, please drop this present patch.
> 

thanks for the links - it sounds very interesting.

As I understood, people trying to enable PPS on am335 device with the
goal to have PPS signal generated on some SoC pin and therefore they use DMtimer.
Also, as i understood, the Timer Load Register (TLDR) is corrected once
a second at each HW_TS_PUSH - as result, if freq was corrected during current sec
there will be some HW_TS_PUSH generation jitter any way.

Above solution is a bit complex for keystone 2 SoCs, as CPTS itself on these SoCs has
output pin (ts_comp) which can be used for PPS signal generation. So, I think,
similar results can be achieved by removing PPS correction code from cpts_ptp_adjfreq()
and updating CPTS_TS_LOAD_VAL once a sec in cpts_overflow_check().

or I missed smth?

-- 
regards,
-grygorii

WARNING: multiple messages have this Message-ID (diff)
From: Grygorii Strashko <grygorii.strashko@ti.com>
To: Richard Cochran <richardcochran@gmail.com>
Cc: Murali Karicheri <m-karicheri2@ti.com>,
	Wingman Kwok <w-kwok2@ti.com>,
	"David S. Miller" <davem@davemloft.net>,
	netdev@vger.kernel.org, Mugunthan V N <mugunthanvnm@ti.com>,
	Sekhar Nori <nsekhar@ti.com>,
	linux-kernel@vger.kernel.org, linux-omap@vger.kernel.org,
	Rob Herring <robh+dt@kernel.org>,
	devicetree@vger.kernel.org
Subject: Re: [PATCH 4/6] net: ethernet: ti: cpts: add ptp pps support
Date: Fri, 2 Dec 2016 11:58:34 -0600	[thread overview]
Message-ID: <bfbebf2d-d057-6a21-845c-48f0a9ab0404@ti.com> (raw)
In-Reply-To: <20161202095848.GA14586@localhost.localdomain>

Hi Richard,

On 12/02/2016 03:58 AM, Richard Cochran wrote:
> On Wed, Nov 30, 2016 at 11:17:38PM +0100, Richard Cochran wrote:
>> On Wed, Nov 30, 2016 at 02:43:57PM -0600, Grygorii Strashko wrote:
>>> Sry, but this is questionable - code for pps comes from TI internal
>>> branches (SDK releases) where it survived for a pretty long time.
> 
> Actually, there is a way to get an accurate PPS from the am335x.  See
> this recent thread:
> 
>    https://www.mail-archive.com/linuxptp-devel@lists.sourceforge.net/msg01726.html
> 
> That is the way to go, and so, please drop this present patch.
> 

thanks for the links - it sounds very interesting.

As I understood, people trying to enable PPS on am335 device with the
goal to have PPS signal generated on some SoC pin and therefore they use DMtimer.
Also, as i understood, the Timer Load Register (TLDR) is corrected once
a second at each HW_TS_PUSH - as result, if freq was corrected during current sec
there will be some HW_TS_PUSH generation jitter any way.

Above solution is a bit complex for keystone 2 SoCs, as CPTS itself on these SoCs has
output pin (ts_comp) which can be used for PPS signal generation. So, I think,
similar results can be achieved by removing PPS correction code from cpts_ptp_adjfreq()
and updating CPTS_TS_LOAD_VAL once a sec in cpts_overflow_check().

or I missed smth?

-- 
regards,
-grygorii

  reply	other threads:[~2016-12-02 17:58 UTC|newest]

Thread overview: 65+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-11-28 23:04 [PATCH 0/6] net: ethernet: ti: cpts: update and enable support on keystone 2 socs Grygorii Strashko
2016-11-28 23:04 ` Grygorii Strashko
2016-11-28 23:04 ` [PATCH 1/6] net: ethernet: ti: netcp: add support of cpts Grygorii Strashko
2016-11-28 23:04   ` Grygorii Strashko
2016-11-30  9:44   ` Richard Cochran
2016-11-30 17:31     ` Grygorii Strashko
2016-11-30 17:31       ` Grygorii Strashko
2016-11-30 17:31       ` Grygorii Strashko
2016-11-30 18:22       ` Richard Cochran
2016-12-05 14:49   ` Rob Herring
2016-12-05 18:25     ` Grygorii Strashko
2016-12-05 18:25       ` Grygorii Strashko
2016-12-05 19:30       ` Richard Cochran
2016-11-28 23:04 ` [PATCH 2/6] net: ethernet: ti: cpts: add support for ext rftclk selection Grygorii Strashko
2016-11-28 23:04   ` Grygorii Strashko
2016-11-30  9:56   ` Richard Cochran
2016-11-30  9:56     ` Richard Cochran
2016-11-30 17:35     ` Grygorii Strashko
2016-11-30 17:35       ` Grygorii Strashko
2016-11-30 17:35       ` Grygorii Strashko
2016-12-06 19:39       ` Grygorii Strashko
2016-12-06 19:39         ` Grygorii Strashko
2016-12-06 20:25         ` Richard Cochran
2016-12-06 20:40           ` Grygorii Strashko
2016-12-06 20:40             ` Grygorii Strashko
2016-12-06 20:40             ` Grygorii Strashko
2016-12-09  0:47         ` Stephen Boyd
2016-12-09 23:29           ` Grygorii Strashko
2016-12-09 23:29             ` Grygorii Strashko
2016-12-09 23:29             ` Grygorii Strashko
2016-12-05 14:51   ` Rob Herring
2016-11-28 23:04 ` [PATCH 3/6] net: ethernet: ti: cpts: add support of cpts HW_TS_PUSH Grygorii Strashko
2016-11-28 23:04   ` Grygorii Strashko
2016-11-30 10:19   ` Richard Cochran
2016-11-30 10:19     ` Richard Cochran
2016-11-30 11:08   ` Jan Lübbe
2016-11-30 20:15     ` Grygorii Strashko
2016-11-30 20:15       ` Grygorii Strashko
2016-12-03 23:21   ` Richard Cochran
2016-12-08 19:04     ` Grygorii Strashko
2016-12-08 19:04       ` Grygorii Strashko
2016-12-08 19:04       ` Grygorii Strashko
2016-12-09  8:50       ` Richard Cochran
2016-11-28 23:04 ` [PATCH 4/6] net: ethernet: ti: cpts: add ptp pps support Grygorii Strashko
2016-11-28 23:04   ` Grygorii Strashko
2016-11-30 10:05   ` Richard Cochran
2016-12-06 18:08     ` Richard Cochran
2016-12-06 18:08       ` Richard Cochran
2016-12-06 20:43       ` Grygorii Strashko
2016-12-06 20:43         ` Grygorii Strashko
2016-11-30 11:01   ` Jan Lübbe
2016-11-30 18:45   ` Richard Cochran
2016-11-30 20:43     ` Grygorii Strashko
2016-11-30 20:43       ` Grygorii Strashko
2016-11-30 22:17       ` Richard Cochran
2016-12-02  9:58         ` Richard Cochran
2016-12-02 17:58           ` Grygorii Strashko [this message]
2016-12-02 17:58             ` Grygorii Strashko
2016-12-02 19:28             ` Richard Cochran
2016-12-02 19:28               ` Richard Cochran
2016-11-28 23:04 ` [PATCH 5/6] ARM: keystone: dts: fix netcp clocks and add names Grygorii Strashko
2016-11-28 23:04   ` Grygorii Strashko
2016-11-28 23:04   ` Grygorii Strashko
2016-11-28 23:04 ` [PATCH 6/6] ARM: dts: keystone: enable time synchronization (cpts) submodule Grygorii Strashko
2016-11-28 23:04   ` Grygorii Strashko

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