netdev - Re: [RFC] Defining a home/maintenance model for non-NIC PHC devices using the /dev/ptpX API

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Message-ID: <ad261f12-82a1-4a02-9abd-a7d7c7e771e8@linux.alibaba.com>
Date: Wed, 14 Jan 2026 20:45:37 +0800
From: Wen Gu <guwen@...ux.alibaba.com>
To: Vadim Fedorenko <vadim.fedorenko@...ux.dev>
Cc: Thomas Gleixner <tglx@...utronix.de>,
 Richard Cochran <richardcochran@...il.com>,
 "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
 LKML <linux-kernel@...r.kernel.org>, Jakub Kicinski <kuba@...nel.org>,
 Dust Li <dust.li@...ux.alibaba.com>, Xuan Zhuo <xuanzhuo@...ux.alibaba.com>,
 Andrew Lunn <andrew+netdev@...n.ch>, David Woodhouse <dwmw2@...radead.org>,
 virtualization@...ts.linux.dev, Nick Shi <nick.shi@...adcom.com>,
 Paolo Abeni <pabeni@...hat.com>, linux-clk@...r.kernel.org,
 Sven Schnelle <svens@...ux.ibm.com>, Andrew Lunn <andrew@...n.ch>
Subject: Re: [RFC] Defining a home/maintenance model for non-NIC PHC devices
 using the /dev/ptpX API



On 2026/1/14 18:50, Vadim Fedorenko wrote:
> On 14/01/2026 09:13, Wen Gu wrote:
>>
>> Thank you all for your suggestions.
>>
>> The drivers under drivers/ptp can be divided into (to my knowledge):
>>
>> 1. Network/1588-oriented clocks, which allow the use of tools like
>>     ptp4l to synchronize the local PHC with an external reference clock
>>     (based on the network or other methods) via the 1588 protocol to
>>     maintain accuracy. Examples include:
>>
>>     - ptp_dte
>>     - ptp_qoriq
>>     - ptp_ines
>>     - ptp_pch
>>     - ptp_idt82p33
>>     - ptp_clockmatrix
>>     - ptp_fc3
>>     - ptp_mock (mock/testing)
>>     - ptp_dfl_tod
>>     - ptp_netc
>>     - ptp_ocp (a special case which provides a grandmaster
>>                clock for a PTP enabled network, generally
>>                serves as the reference clock)
> 
> ptp_ocp is a timecard driver, which doesn't require calibration by
> ptp4l/ts2phc. OCP TimeCards have their own Atomic Clock onboard which
> is disciplined by 1-PPS or 10mhz signal from configurable source. The
> disciplining algorithm is implemented in Atomic Clock package
> controller. The driver exposes ptp device mostly for reading the time.
> So I believe it belongs to group 2 rather than 1588 group.
> 

Thank you for the correction and detailed explanation. I will move
ptp_ocp to group 2.

>>
>> 2. Platform/infrastructure/hypervisor-provided clocks. They don't
>>     require calibration by ptp4l based on 1588 and reference clocks,
>>     instead the underlay handle this. Users generally read the time.
>>     They include:
>>
>>     - ptp_kvm
>>     - ptp_vmclock
>>     - ptp_vmw
>>     - ptp_s390
>>     - ptp_cipu (upstreaming)
>>
>>  From this perspective, I agree that "emulating" could be an appropriate
>> name for the second ones.
>>
>> And I would like to further group the first ones to "1588", thus
>> divide drivers/ptp to:
>>
>> - drivers/ptp/core
>> - drivers/ptp/1588
>> - drivers/ptp/emulating
>>
>> Regards.