Re: [PATCH net-next v7 15/16] net: ethtool: ts: Let the active time stamping layer be selectable

[Rahul Rameshbabu <rrameshbabu@nvidia.com>]

On Wed, 29 Nov, 2023 15:56:13 -0800 Jakub Kicinski <kuba@kernel.org> wrote:
> On Wed, 29 Nov 2023 23:00:34 +0100 Köry Maincent wrote:
>> > Not sure why you say "not used", though. Are you not planning to expose
>> > the qualifier as an attribute to the listing of hwtstamp providers
>> > offered to user space by ETHTOOL_MSG_TSINFO_GET?  
>> 
>> Yes I will, I was just saying that all the PHC would be set as precise for now.
>> Approximate timestamp quality won't be used because IIUC there are no NIC driver
>> supporting it yet.
>
> Agreed that we should add the attr from the start.
>
> Maybe we can ask/work with Rahul <rrameshbabu@nvidia.com>
> to implement the right thing in mlx5?

Thanks for looping me in. We were already looking at this patch series
out of interest. I saw your suggestion to rephrase "MAC / DMA" as
"precise / approximate", which we really like for mlx5 devices because
our "approximate" timestamping logic is not exactly a "MAC" timestamp
but its not a port timestamp that has the greater precision we use. I
have a task already for implementing support for this ethtool attribute.
If folks here are open to it, I can add mlx5 support for both modes in
this patch series for the next revision that will entail the discussed
changes.

>
> Failing that we can mark mlx5 as imprecise, until its sorted out.
> So that we have both types in the tree.

--
Thanks,

Rahul Rameshbabu