Re: [RFC PATCH net-next v4 1/2] macb: Add 1588 support in Cadence GEM.

From	Nicolas Ferre <nicolas.ferre@atmel.com>
Newsgroups	linux.kernel
Subject	Re: [RFC PATCH net-next v4 1/2] macb: Add 1588 support in Cadence GEM.
Date	2017-01-03 15:30 +0100
Message-ID	<sVyga-7AS-31@gated-at.bofh.it> (permalink)
References	(2 earlier) <sV986-6ct-33@gated-at.bofh.it> <sVc5X-843-3@gated-at.bofh.it> <sVdv3-YY-3@gated-at.bofh.it> <sVpwd-16x-3@gated-at.bofh.it> <sVuPf-4XV-15@gated-at.bofh.it>
Organization	atmel

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Le 03/01/2017 à 11:47, Rafal Ozieblo a écrit :
>> From: Harini Katakam [mailto:harinikatakamlinux@gmail.com] 
>> Sent: 3 stycznia 2017 06:06
>> Subject: Re: [RFC PATCH net-next v4 1/2] macb: Add 1588 support in Cadence GEM.
>>
>> Hi Richard,
>>
>> On Mon, Jan 2, 2017 at 9:43 PM, Richard Cochran <richardcochran@gmail.com> wrote:
>>> On Mon, Jan 02, 2017 at 03:47:07PM +0100, Nicolas Ferre wrote:
>>>> Le 02/01/2017 à 12:31, Richard Cochran a écrit :
>>>>> This Cadence IP core is a complete disaster.
>>>>
>>>> Well, it evolved and propose several options to different SoC 
>>>> integrators. This is not something unusual...
>>>> I suspect as well that some other network adapters have the same 
>>>> weakness concerning PTP timestamp in single register as the early 
>>>> revisions of this IP.
>>>
>>> It appears that this core can neither latch the time on read or write, 
>>> or even latch time stamps.  I have worked with many different PTP HW 
>>> implementations, even early ones like on the ixp4xx, and it is no 
>>> exaggeration to say that this one is uniquely broken.
>>>
>>>> I suspect that Rafal tend to jump too quickly to the latest IP 
>>>> revisions and add more options to this series: let's not try to pour 
>>>> too much things into this code right now.
>>>
>>> Why can't you check the IP version in the driver?
>>
>> There is an IP revision register but it would be probably be
>> better to rely on "caps" from the compatibility strings - to cover SoC specific
>> implementations. Also, when this extended BD is added (with timestamp),
>> additional words will need to be added statically which will be
>> consistent with Andrei's CONFIG_ checks.
> We can distinguish IP cores with and without PTP support by reading
> Design Configuration Register. But to distinguish IP cores with
> timestamps in buffer descriptors and which support only event
> registers, we can only check IP version by reading the revision ID
> register and base on that.
> I agree with Harini, compatibility strings could be better. But we
> might end up with many different configuration in the future.

Compatibility strings and associated configurations are cheap. It's not
a problem to have many different configurations and clearer for this
particular "composite" feature.

> We could use only descriptor approach but there are many Atmel's
> cores on the market which support only event registers.

Yes and once in silicon, it's hard to modify ;-)

Regards,
-- 
Nicolas Ferre

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[RFC PATCH net-next v4 1/2] macb: Add 1588 support in Cadence GEM. Andrei Pistirica <andrei.pistirica@microchip.com> - 2016-12-14 11:10 +0100
  Re: [RFC PATCH net-next v4 1/2] macb: Add 1588 support in Cadence  GEM. Richard Cochran <richardcochran@gmail.com> - 2016-12-28 09:20 +0100
  RE: [RFC PATCH net-next v4 1/2] macb: Add 1588 support in Cadence  GEM. Rafal Ozieblo <rafalo@cadence.com> - 2016-12-28 16:00 +0100
  RE: [RFC PATCH net-next v4 1/2] macb: Add 1588 support in Cadence  GEM. Rafal Ozieblo <rafalo@cadence.com> - 2017-01-02 10:40 +0100
    Re: [RFC PATCH net-next v4 1/2] macb: Add 1588 support in Cadence  GEM. Richard Cochran <richardcochran@gmail.com> - 2017-01-02 12:40 +0100
      Re: [RFC PATCH net-next v4 1/2] macb: Add 1588 support in Cadence GEM. Harini Katakam <harinikatakamlinux@gmail.com> - 2017-01-02 12:50 +0100
        Re: [RFC PATCH net-next v4 1/2] macb: Add 1588 support in Cadence  GEM. Richard Cochran <richardcochran@gmail.com> - 2017-01-02 17:10 +0100
      Re: [RFC PATCH net-next v4 1/2] macb: Add 1588 support in Cadence  GEM. Nicolas Ferre <nicolas.ferre@atmel.com> - 2017-01-02 15:50 +0100
        Re: [RFC PATCH net-next v4 1/2] macb: Add 1588 support in Cadence  GEM. Richard Cochran <richardcochran@gmail.com> - 2017-01-02 17:20 +0100
          Re: [RFC PATCH net-next v4 1/2] macb: Add 1588 support in Cadence GEM. Harini Katakam <harinikatakamlinux@gmail.com> - 2017-01-03 06:10 +0100
            Re: [RFC PATCH net-next v4 1/2] macb: Add 1588 support in Cadence  GEM. Richard Cochran <richardcochran@gmail.com> - 2017-01-03 11:30 +0100
            Re: [RFC PATCH net-next v4 1/2] macb: Add 1588 support in Cadence  GEM. Richard Cochran <richardcochran@gmail.com> - 2017-01-03 11:40 +0100
              Re: [RFC PATCH net-next v4 1/2] macb: Add 1588 support in Cadence GEM. Harini Katakam <harinikatakamlinux@gmail.com> - 2017-01-03 12:00 +0100
            Re: [RFC PATCH net-next v4 1/2] macb: Add 1588 support in Cadence  GEM. Richard Cochran <richardcochran@gmail.com> - 2017-01-03 12:20 +0100
              RE: [RFC PATCH net-next v4 1/2] macb: Add 1588 support in Cadence  GEM. <Andrei.Pistirica@microchip.com> - 2017-01-11 15:40 +0100
            RE: [RFC PATCH net-next v4 1/2] macb: Add 1588 support in Cadence  GEM. Rafal Ozieblo <rafalo@cadence.com> - 2017-01-03 11:50 +0100
              Re: [RFC PATCH net-next v4 1/2] macb: Add 1588 support in Cadence  GEM. Nicolas Ferre <nicolas.ferre@atmel.com> - 2017-01-03 15:30 +0100

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