Subject: Re: [PATCH] i40e: fix the wrong PTP frequency calculation

From: Yajun Deng <[email-masked]>
Date: Tue, 26 Sep 2023 09:54:29 +0800

On 2023/9/26 07:59, Tony Nguyen wrote:
> On 9/25/2023 12:55 AM, Yajun Deng wrote:
>>
>> On 2023/6/28 04:20, Jacob Keller wrote:
>>>
>>> On 6/26/2023 7:26 PM, Yajun Deng wrote:
>>>> The new adjustment should be based on the base frequency, not the
>>>> I40E_PTP_40GB_INCVAL in i40e_ptp_adjfine().
>>>>
>>>> This issue was introduced in commit 3626a690b717 ("i40e: use
>>>> mul_u64_u64_div_u64 for PTP frequency calculation"), and was fixed in
>>>> commit 1060707e3809 ("ptp: introduce helpers to adjust by scaled
>>>> parts per million"). However the latter is a new feature and hasn't 
>>>> been
>>>> backported to the stable releases.
>>>>
>>>> This issue affects both v6.0 and v6.1 versions, and the v6.1 
>>>> version is
>>>> an LTS version.
>>>>
>
> ...
>
>>>
>>> Thanks for finding and fixing this mistake. I think its the simplest 
>>> fix
>>> to get into the stable kernel that are broken, since taking the
>>> adjust_by_scaled_ppm version would require additional patches.
>>>
>>> Reviewed-by: Jacob Keller <[email-masked]>
>>>
>> Kindly ping...
>
> As this patch looks to be for stable, you need to follow the process 
> for that. I believe your situation would fall into option 3:
> https://www.kernel.org/doc/html/latest/process/stable-kernel-rules.html#option-3 
>
>
Yes, it needs an upstream commit ID. But this patch didn't need to apply 
to the upstream.

As the commit of the patch, the issue was fixed in
commit 1060707e3809 ("ptp: introduce helpers to adjust by scaled
parts per million"). However the commit is a new feature and hasn't been
backported to the stable releases.

Therefore, the patch does not have an upstream commit ID, and only needs 
to be applied to stable.

> Thanks,
> Tony