linux-kernel - Re: [PATCH] i40e: fix the wrong PTP frequency calculation

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Message-ID: <ef08645e-9891-0d12-2c87-39ce0be52aee@linux.dev>
Date:   Tue, 26 Sep 2023 09:54:29 +0800
From:   Yajun Deng <yajun.deng@...ux.dev>
To:     Tony Nguyen <anthony.l.nguyen@...el.com>,
        Jacob Keller <jacob.e.keller@...el.com>,
        jesse.brandeburg@...el.com, davem@...emloft.net,
        edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com,
        richardcochran@...il.com
Cc:     intel-wired-lan@...ts.osuosl.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, stable@...r.kernel.org
Subject: Re: [PATCH] i40e: fix the wrong PTP frequency calculation


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 <jacob.e.keller@...el.com>
>>>
>> 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