netdev - Re: [PATCH net-next 4/9] mlxsw: reg: Add Management UTC Register

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Date:   Thu, 6 Jun 2019 09:11:29 +0000
From:   Shalom Toledo <shalomt@...lanox.com>
To:     Richard Cochran <richardcochran@...il.com>
CC:     Ido Schimmel <idosch@...sch.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "davem@...emloft.net" <davem@...emloft.net>,
        Jiri Pirko <jiri@...lanox.com>,
        Petr Machata <petrm@...lanox.com>, mlxsw <mlxsw@...lanox.com>,
        Ido Schimmel <idosch@...lanox.com>
Subject: Re: [PATCH net-next 4/9] mlxsw: reg: Add Management UTC Register

On 06/06/2019 5:37, Richard Cochran wrote:
> On Wed, Jun 05, 2019 at 06:55:18PM +0000, Shalom Toledo wrote:
>> On 05/06/2019 20:23, Richard Cochran wrote:
>>> On Wed, Jun 05, 2019 at 11:30:06AM +0000, Shalom Toledo wrote:
>>>> On 04/06/2019 17:17, Richard Cochran wrote:
>>>>> On Mon, Jun 03, 2019 at 03:12:39PM +0300, Ido Schimmel wrote:
>>>>>> From: Shalom Toledo <shalomt@...lanox.com>
>>>>>>
>>>>>> The MTUTC register configures the HW UTC counter.
>>>>>
>>>>> Why is this called the "UTC" counter?
>>>>>
>>>>> The PTP time scale is TAI.  Is this counter intended to reflect the
>>>>> Linux CLOCK_REALTIME system time?
>>>>
>>>> Exactly. The hardware doesn't have the ability to convert the FRC to UTC, so
>>>> we, as a driver, need to do it and align the hardware with this value.
>>>
>>> What does "FRC" mean?
>>
>> Free Running Counter
> 
> Okay, so then you want to convert it into TAI (for PTP) rather than UTC.

No, the HW interface is in UTC format. This is part of the HW machine that
responsible for adding the UTC time stamping on R-SPAN mirror packets.

> 
> Thanks,
> Richard
>