linux-kernel - RE: [EXTERNAL] [PATCH] net: fec: Refactor MAC reset to function

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Message-ID:
 <DM4PR17MB59691A9B9E59DD9D1F6493BBDFE12@DM4PR17MB5969.namprd17.prod.outlook.com>
Date: Wed, 22 Jan 2025 15:22:53 +0000
From: "Badel, Laurent" <LaurentBadel@...on.com>
To: Csókás Bence <csokas.bence@...lan.hu>, Jakub Kicinski
	<kuba@...nel.org>, "imx@...ts.linux.dev" <imx@...ts.linux.dev>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC: Wei Fang <wei.fang@....com>, Shenwei Wang <shenwei.wang@....com>, Clark
 Wang <xiaoning.wang@....com>, Andrew Lunn <andrew+netdev@...n.ch>, "David S.
 Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, Paolo
 Abeni <pabeni@...hat.com>
Subject: RE: [EXTERNAL] [PATCH] net: fec: Refactor MAC reset to function

Hi Bence, thank you for your explanations. It's clearer to me now what you
aim to achieve here. 

> To me, the name `FEC_QUIRK_NO_HARD_RESET`, and its doc-comment seems to
> suggest that we do *not* want to hard-reset this MAC *ever*; not in the
> codepath of `fec_restart()` and not in `fec_stop()`. 

Perhaps a bit misleading I have to agree. It's really only meant to avoid 
the link being dropped due to the hard reset, which I don't think is a 
concern in fec_stop().

> Did you observe
> problems on i.MX28 if you soft-reset it in stop()? I _might_ be able to
> get my hands on an i.MX287 and test, but I have no idea if it is
> working; I took it out from the junk bin.

I did not observe any problems. I just tested it today on iMX28 (which is 
the only SoC currently bearing the FEC_QUIRK_NO_HARD_RESET flag - iMX27 is 
a different family so I'm not sure if it is needed in that case) and it 
works fine, I can bring the interface down and back up, pull the cord, 
change the pause settings, all without any apparent change in behavior. 

I tested on the 5.10.233 tag which is the branch I am using. For 
completeness I am currently trying to test it on 6.13 but it will take some
time for the build to complete so I will report later in the unlikely case
I find an issue.

If there is any other relevant tests you have in mind, please let me know 
and I'll try it out if possible.

I don't think there is any significant risk in changing from hard to soft 
reset because it only applies to iMX28 and the hard reset should be asserted
on the next call to fec_restart() anyway.  Given the stated reason for the 
modification and some basic test results, my opinion is now that we can 
proceed with the modification.

Best regards,

Laurent