netdev - Re: [PATCH v2] net: fec: Add ECR bit macros, fix FEC_ECR

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Date: Tue, 11 Jun 2024 10:04:39 +0200
From: Csókás Bence <csokas.bence@...lan.hu>
To: Andrew Lunn <andrew@...n.ch>
CC: <imx@...ts.linux.dev>, <netdev@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, Wei Fang <wei.fang@....com>, Shenwei Wang
	<shenwei.wang@....com>, Clark Wang <xiaoning.wang@....com>, "David S. Miller"
	<davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski
	<kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, Richard Cochran
	<richardcochran@...il.com>
Subject: Re: [PATCH v2] net: fec: Add ECR bit macros, fix FEC_ECR_EN1588 being
 cleared on link-down

Hi!

On 6/10/24 21:13, Andrew Lunn wrote:
> On Fri, Jun 07, 2024 at 10:18:55AM +0200, Csókás, Bence wrote:
>> FEC_ECR_EN1588 bit gets cleared after MAC reset in `fec_stop()`, which
>> makes all 1588 functionality shut down on link-down. However, some
>> functionality needs to be retained (e.g. PPS) even without link.
> 
> I don't know much about PPS. Could you point to some documentation,
> list email etc, which indicated PPS without link is expected to work.
> 
> Please also Cc: Richard Cochran for changes like this.
> 
> Thanks
> 	Andrew

This is what Richard said two years ago on the now-reverted patch:

Link: https://lore.kernel.org/netdev/YvRdTwRM4JBc5RuV@hoboy.vegasvil.org

 > IMO the least surprising behavior is that once enabled, a feature
 > stays on until explicitly disabled.

The point of PPS is, it is a 1 Hz clock reference. We don't want to take 
away a clock signal because of an unexpected link fault, for instance.

Plus, this patch doesn't even re-enable PPS or any other 1588 functions, 
it just prevents the adapter from forgetting it is even 1588-capable. 
I'll resubmit with more clear wording and appropriate "Fixes:" and "Cc:" 
tags.

Bence