linux-kernel - RE: [PATCH net] net: phy: Micrel KSZ8061: fix errata solution not taking effect problem

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Message-ID: <BYAPR11MB35587571DADF73195961A9DFECF32@BYAPR11MB3558.namprd11.prod.outlook.com>
Date: Thu, 30 May 2024 22:42:23 +0000
From: <Tristram.Ha@...rochip.com>
To: <pabeni@...hat.com>
CC: <davem@...emloft.net>, <edumazet@...gle.com>, <kuba@...nel.org>,
	<UNGLinuxDriver@...rochip.com>, <netdev@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, <andrew@...n.ch>, <hkallweit1@...il.com>,
	<linux@...linux.org.uk>
Subject: RE: [PATCH net] net: phy: Micrel KSZ8061: fix errata solution not
 taking effect problem

> Subject: Re: [PATCH net] net: phy: Micrel KSZ8061: fix errata solution not taking effect
> problem
> 
> On Tue, 2024-05-28 at 14:37 -0700, Tristram.Ha@...rochip.com wrote:
> > From: Tristram Ha <tristram.ha@...rochip.com>
> >
> > KSZ8061 needs to write to a MMD register at driver initialization to fix
> > an errata.  This worked in 4.14 kernel but not in newer kernels.  The
> > issue is the main phylib code no longer resets PHY at the very beginning.
> > Calling phy resuming code later will reset the chip if it is already
> > powered down at the beginning.  This wipes out the MMD register write.
> > Solution is to implement a phy resume function for KSZ8061 to take care
> > of this problem.
> >
> > Fixes: 232ba3a51cc2 ("net: phy: Micrel KSZ8061: link failure after cable connect")
> 
> As the blamed commit belongs to 5.0 and the changelog hints anything
> after 4.14 is broken, it looks like there is an inconsistency. Please
> fix the changelog or the tag.

A customer reported this problem and said they were using 4.14 and cited
this commit, so I assumed it was added in that kernel.  Indeed 4.19
kernel has this code, so it was probably backported.

I will update the comment.