netdev - Re: [PATCH net-next 2/5] eth: fbnic: add initial PHC support

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Message-ID: <c1003a1b-cf6f-4332-b0c7-5461a164097e@linux.dev>
Date: Wed, 11 Sep 2024 20:49:51 +0100
From: Vadim Fedorenko <vadim.fedorenko@...ux.dev>
To: Andrew Lunn <andrew@...n.ch>
Cc: Jakub Kicinski <kuba@...nel.org>, David Ahern <dsahern@...nel.org>,
 Paolo Abeni <pabeni@...hat.com>, "David S. Miller" <davem@...emloft.net>,
 Alexander Duyck <alexanderduyck@...com>, netdev@...r.kernel.org
Subject: Re: [PATCH net-next 2/5] eth: fbnic: add initial PHC support

On 11/09/2024 17:25, Andrew Lunn wrote:
> It appears that Richard has not been Cc:ed.

Ah, will do it in v2 for sure

>> +/* FBNIC timing & PTP implementation
>> + * Datapath uses truncated 40b timestamps for scheduling and event reporting.
>> + * We need to promote those to full 64b, hence we periodically cache the top
>> + * 32bit of the HW time counter. Since this makes our time reporting non-atomic
>> + * we leave the HW clock free running and adjust time offsets in SW as needed.
>> + * Time offset is 64bit - we need a seq counter for 32bit machines.
>> + * Time offset and the cache of top bits are independent so we don't need
>> + * a coherent snapshot of both - READ_ONCE()/WRITE_ONCE() + writer side lock
>> + * are enough.
>> + *
>> + * TBD: alias u64_stats_sync & co. with some more appropriate names upstream.
> 
> This is upstream, so maybe now is a good time to decide?

That's good question. Do we need another set of helpers just because of 
names? Obviously, the internals will be the same sequence magic.