linux-kernel - Re: [PATCH net-next v4] ptp: add Alibaba CIPU PTP clock driver

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Message-ID: <2a98165b-a353-405d-83e0-ffbca1d41340@linux.alibaba.com>
Date: Sat, 16 Aug 2025 11:52:18 +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, Thomas Gleixner <tglx@...utronix.de>,
 David Woodhouse <dwmw2@...radead.org>
Subject: Re: [PATCH net-next v4] ptp: add Alibaba CIPU PTP clock driver



On 2025/8/16 02:38, Jakub Kicinski wrote:
> On Tue, 12 Aug 2025 19:53:21 +0800 Wen Gu wrote:
>> This adds a driver for Alibaba CIPU PTP clock. The CIPU, an underlying
>> infrastructure of Alibaba Cloud, synchronizes time with reference clocks
>> continuously and provides PTP clocks for VMs and bare metals in cloud.
> 
>> +static struct attribute *ptp_cipu_attrs[] = {
>> +	&dev_attr_reg_dev_feat.attr,
>> +	&dev_attr_reg_gst_feat.attr,
>> +	&dev_attr_reg_drv_ver.attr,
>> +	&dev_attr_reg_env_ver.attr,
>> +	&dev_attr_reg_dev_stat.attr,
>> +	&dev_attr_reg_sync_stat.attr,
>> +	&dev_attr_reg_tm_prec_ns.attr,
>> +	&dev_attr_reg_epo_base_yr.attr,
>> +	&dev_attr_reg_leap_sec.attr,
>> +	&dev_attr_reg_max_lat_ns.attr,
>> +	&dev_attr_reg_mt_tout_us.attr,
>> +	&dev_attr_reg_thresh_us.attr,
>> +
>> +	&dev_attr_ptp_gettm.attr,
>> +	&dev_attr_ptp_gettm_inval_err.attr,
>> +	&dev_attr_ptp_gettm_tout_err.attr,
>> +	&dev_attr_ptp_gettm_excd_thresh.attr,
>> +
>> +	&dev_attr_dev_clk_abn.attr,
>> +	&dev_attr_dev_clk_abn_rec.attr,
>> +	&dev_attr_dev_maint.attr,
>> +	&dev_attr_dev_maint_rec.attr,
>> +	&dev_attr_dev_maint_tout.attr,
>> +	&dev_attr_dev_busy.attr,
>> +	&dev_attr_dev_busy_rec.attr,
>> +	&dev_attr_dev_err.attr,
>> +	&dev_attr_dev_err_rec.attr,
> 
> This driver is lacking documentation. You need to describe how the user
> is expected to interact with the device and document all these sysfs
> attributes.
> 

OK. I will add the description.

Would you prefer me to create a related .rst file under Documentation/
(perhaps in a new Documentation/clock/ptp/ directory?), or add the
description comments directly in this driver source?

> Maybe it's just me, but in general I really wish someone stepped up
> and created a separate subsystem for all these cloud / vm clocks.
> They have nothing to do with PTP. In my mind PTP clocks are simple HW
> tickers on which we build all the time related stuff. While this driver
> reports the base year for the epoch and leap second status via sysfs.

These sysfs are intended to provide diagnostics and informations.
For users, interacting with this PTP clock works the same way as with other
PTP clock, through the exposed chardev. The 1588 protocol related work has
been done by the cloud infra so the driver only reads some registers.

Thanks.