netdev - Re: Regression in KSZ9477 dsa driver - KSZ9567 et al. do not support EEE

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Message-ID: <ZrGv3BEWnfaro39W@pengutronix.de>
Date: Tue, 6 Aug 2024 07:08:44 +0200
From: Oleksij Rempel <o.rempel@...gutronix.de>
To: Jakub Kicinski <kuba@...nel.org>
Cc: lukma@...x.de, Martin Whitaker <foss@...tin-whitaker.me.uk>,
	woojung.huh@...rochip.com, UNGLinuxDriver@...rochip.com,
	netdev@...r.kernel.org
Subject: Re: Regression in KSZ9477 dsa driver - KSZ9567 et al. do not support
 EEE

Hi Martin,

On Mon, Aug 05, 2024 at 01:54:55PM -0700, Jakub Kicinski wrote:
> On Mon, 5 Aug 2024 13:15:49 +0100 Martin Whitaker wrote:
> > I have an embedded processor board running Linux that incorporates a
> > KSZ9567 ethernet switch. When using Linux 6.1 I can establish a stable
> > connection between two of these boards. When using Linux 6.6, the link
> > repeatedly drops and reconnects every few seconds.
> > 
> >  From bisection, this bug was introduced in the patch series "net: add
> > EEE support for KSZ9477 switch family" which was merged in commit
> > 9b0bf4f77162.
> > 
> > As noted in the errata for these devices, EEE support is not fully
> > operational in the KSZ9477, KSZ9567, KSZ9896, and KSZ9897 devices,
> > causing link drops when connected to another device that supports EEE.
> > 
> > A fix for this regression was merged in commit 08c6d8bae48c2, but only
> > for the KSZ9477. This fix should be extended to the other affected
> > devices as follows:
> 
> Thanks for the analysis, adding to CC the folks who wrote the commits
> you mention.

Thank you!

> > diff --git a/drivers/net/dsa/microchip/ksz_common.c
> > b/drivers/net/dsa/microchip/ksz_common.c
> > index 419476d07fa2..091dae6ac921 100644
> > --- a/drivers/net/dsa/microchip/ksz_common.c
> > +++ b/drivers/net/dsa/microchip/ksz_common.c
> > @@ -2346,6 +2346,9 @@ static u32 ksz_get_phy_flags(struct dsa_switch
> > *ds, int port)
> >                          return MICREL_KSZ8_P1_ERRATA;
> >                  break;
> >          case KSZ9477_CHIP_ID:
> > +       case KSZ9567_CHIP_ID:
> > +       case KSZ9896_CHIP_ID:
> > +       case KSZ9897_CHIP_ID:
> >                  /* KSZ9477 Errata DS80000754C
> >                   *
> >                   * Module 4: Energy Efficient Ethernet (EEE) feature
> > select must
> > 
> > I have verified this fixes the bug for the KSZ9567 on my board.

I can confirm it, Microchip officially removed EEE support from the
datasheets for this chips and extended errata documentations.

KSZ9567S-Errata-DS80000756.pdf
Module 4: Energy Efficient Ethernet (EEE) feature select must be manually disabled

KSZ9896C-Errata-DS80000757.pdf
Module 3: Energy Efficient Ethernet (EEE) feature select must be manually disabled

KSZ9897S-Errata-DS80000759.pdf
Module 4: Energy Efficient Ethernet (EEE) feature select must be manually disabled

Would you like to send this patch against net and add references to this erratum
to the code?

Regards,
Oleksij
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