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

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Message-ID: <8a74f801-1de5-4a1d-adc7-66a91221485d@linux.alibaba.com>
Date: Wed, 5 Nov 2025 18:22:19 +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 2025/11/1 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.

> 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.

Regards.