netdev - Re: [PATCH net-next 2/3] net: stmmac: Allow supporting coarse adjustment mode

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Message-ID: <ac505a82-1a01-4c1d-8f9b-826133a07ecf@bootlin.com>
Date: Thu, 23 Oct 2025 10:29:26 +0200
From: Maxime Chevallier <maxime.chevallier@...tlin.com>
To: Jakub Kicinski <kuba@...nel.org>
Cc: Alexandre Torgue <alexandre.torgue@...s.st.com>,
 Jose Abreu <joabreu@...opsys.com>, Andrew Lunn <andrew+netdev@...n.ch>,
 davem@...emloft.net, Eric Dumazet <edumazet@...gle.com>,
 Paolo Abeni <pabeni@...hat.com>, Maxime Coquelin
 <mcoquelin.stm32@...il.com>, Richard Cochran <richardcochran@...il.com>,
 Russell King <linux@...linux.org.uk>,
 Köry Maincent <kory.maincent@...tlin.com>,
 Alexis Lothoré <alexis.lothore@...tlin.com>,
 Thomas Petazzoni <thomas.petazzoni@...tlin.com>, netdev@...r.kernel.org,
 linux-stm32@...md-mailman.stormreply.com,
 linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next 2/3] net: stmmac: Allow supporting coarse
 adjustment mode



On 22/10/2025 01:02, Jakub Kicinski wrote:
> On Tue, 21 Oct 2025 10:02:01 +0200 Maxime Chevallier wrote:
>> Let me know if you need more clarifications on this
> 
> The explanation was excellent, thank you. I wonder why it's designed
> in such an odd way, instead of just having current_time with some
> extra/fractional bits not visible in the timestamp. Sigh.
> 
> In any case, I don't feel strongly but it definitely seems to me like
> the crucial distinction here is not the precision of the timestamp but
> whether the user intends to dial the frequency.

Yes indeed. I don't have a clear view on wether this is something unique
to stmmac or if this is common enough to justify using the tsconfig API.

As we discuss this, I would tend to think devlink is the way, as this
all boils down to how this particular HW works. Moreover, if we use a
dedicated hwprov qualifier, where do we make it sit in the current
hierarchy (precise > approx) that's used for the TS source selection ?

Maxime