linux-kernel - Re: [PATCH net-next v5 1/2] ptp: introduce Alibaba CIPU PHC driver

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Message-ID: <34b30157-6d67-46ec-abde-da9087fbf318@linux.alibaba.com>
Date: Thu, 27 Nov 2025 13:48:47 +0800
From: Wen Gu <guwen@...ux.alibaba.com>
To: Jakub Kicinski <kuba@...nel.org>
Cc: richardcochran@...il.com, andrew+netdev@...n.ch, davem@...emloft.net,
 edumazet@...gle.com, pabeni@...hat.com, xuanzhuo@...ux.alibaba.com,
 dust.li@...ux.alibaba.com, netdev@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next v5 1/2] ptp: introduce Alibaba CIPU PHC driver



On 2025/11/6 08:24, Jakub Kicinski wrote:
> On Wed, 5 Nov 2025 18:22:19 +0800 Wen Gu wrote:
>> On 2025/11/1 07:58, Jakub Kicinski wrote:
>>> On Thu, 30 Oct 2025 20:13:13 +0800 Wen Gu wrote:
>>>> This adds a driver for Alibaba CIPU PTP clock. The CIPU, an underlying
>>>> infrastructure of Alibaba Cloud, synchronizes time with atomic clocks
>>>> via the network and provides microsecond or sub-microsecond precision
>>>> timestamps for VMs and bare metals on cloud.
>>>>
>>>> User space processes, such as chrony, running in VMs or on bare metals
>>>> can get the high precision time through the PTP device exposed by this
>>>> driver.
>>>
>>> As mentioned on previous revisions this is a pure clock device which has
>>> nothing to do with networking and PTP.
>>
>> I don't quite agree that this has nothing to do with PTP.
>>
>> What is the difference between this CIPU PTP driver and other PTP drivers
>> under drivers/ptp? such as ptp_s390, ptp_vmw, ptp_pch, and others. Most of
>> these PTP drivers do not directly involve IEEE 1588 or networking as well.
> 

Sorry for the late reply due to a vacation.

> We can't delete existing drivers. It used to be far less annoying
> until every cloud vendor under the sun decided to hack up their own
> implementation of something as simple as the clock.
> 

So what kind of drivers do you think are qualified to be placed in the
drivers/ptp? I checked some docs, e.g.[1], and codes in drivers/ptp,
but I am not sure what the deciding factor is, assuming that exposing
a PTP character device is not sufficient.

[1] https://docs.kernel.org/driver-api/ptp.html

Regards.

>>> There should be a separate class
>>> for "hypervisor clocks", if not a common driver.
>>
>> 'hypervisor clock' is not very accurate. CIPU PTP can be used in VM and
>> bare metal scenarios, and bare metals do not need hypervisors.
> 
> I know.