netdev - Re: [RFC PATCH v4 0/4] Create common DPLL/clock configuration API

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Message-ID: <Y5MHlrZYe11ZglUS@nanopsycho>
Date:   Fri, 9 Dec 2022 11:01:58 +0100
From:   Jiri Pirko <jiri@...nulli.us>
To:     "Kubalewski, Arkadiusz" <arkadiusz.kubalewski@...el.com>
Cc:     Vadim Fedorenko <vfedorenko@...ek.ru>,
        Jakub Kicinski <kuba@...nel.org>,
        Jonathan Lemon <jonathan.lemon@...il.com>,
        Paolo Abeni <pabeni@...hat.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-clk@...r.kernel.org" <linux-clk@...r.kernel.org>
Subject: Re: [RFC PATCH v4 0/4] Create common DPLL/clock configuration API

Fri, Dec 09, 2022 at 12:05:43AM CET, arkadiusz.kubalewski@...el.com wrote:
>>From: Jiri Pirko <jiri@...nulli.us>
>>Sent: Thursday, December 8, 2022 12:59 PM
>>
>>>>From: Jiri Pirko <jiri@...nulli.us>
>>>>Sent: Friday, December 2, 2022 5:12 PM
>>>>
>>>>Fri, Dec 02, 2022 at 12:27:24PM CET, arkadiusz.kubalewski@...el.com
>>wrote:
>>>>>>From: Jiri Pirko <jiri@...nulli.us>
>>>>>>Sent: Wednesday, November 30, 2022 1:32 PM
>>>>>>
>>>>>>Tue, Nov 29, 2022 at 10:37:20PM CET, vfedorenko@...ek.ru wrote:

[...]

>>>>This you have to clearly specify when you define driver API.
>>>>This const attrs should be passed during pin creation/registration.
>>>>
>>>>Talking about dpll instance itself, the clock_id, clock_quality, these
>>>>should be also const attrs.
>>>>
>>>
>>>Actually, clock_quality can also vary on runtime (i.e. ext/synce). We
>>cannot
>>>determine what Quality Level signal user has connected to the SMA or was
>>>received from the network. Only gnss/oscilattor could have const depending
>>>on used HW. But generally it shall not be const.
>>
>>Sec. I'm talkign about the actual dpll quality, means the internal
>>clock. How it can vary?
>
>Yes, the DPLL has some holdover capacity, thus can translate this into QL and
>it shall not ever change. Sure, we could add this.
>
>I was thinking about a source Quality Level. If that would be available here,
>the ptp-profiles implementation would be simpler, as ptp daemon could read it
>and embed that information in its frames.
>Although, this would have to be configurable from user space, at least for EXT
>and SYNCE pin types.

The kernel would serve as a holder or info shared from one daemon to
another one. That does not sound correct. PTP should ask SyncE deamon
directly, I believe.