netdev - Re: [PATCH 3/4] net: dsa: microchip: check erratum workaround through indirect register read

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Message-ID: <CAHvy4ArmWx78aP=2O1a2F=GXqro2N6GxjdYO+AGs32petpL4+Q@mail.gmail.com>
Date: Thu, 18 Jul 2024 15:45:13 +0200
From: Pieter <vtpieter@...il.com>
To: Andrew Lunn <andrew@...n.ch>
Cc: devicetree@...r.kernel.org, woojung.huh@...rochip.com, 
	UNGLinuxDriver@...rochip.com, netdev@...r.kernel.org, o.rempel@...gutronix.de, 
	Pieter Van Trappen <pieter.van.trappen@...n.ch>
Subject: Re: [PATCH 3/4] net: dsa: microchip: check erratum workaround through
 indirect register read

On Thu, Jul 18, 2024 at 04:24, Andrew Lunn <andrew@...n.ch> wrote :
> On Wed, Jul 17, 2024 at 09:37:24PM +0200, vtpieter@...il.com wrote:
> > From: Pieter Van Trappen <pieter.van.trappen@...n.ch>
> >
> > Check the erratum workaround application which ensures in addition
> > that indirect register write and read work as expected.
> >
> > Commit b7fb7729c94f ("net: dsa: microchip: fix register write order in
> > ksz8_ind_write8()") would have been found faster like this.
> >
> > Also fix the register naming as in the datasheet.
>
> We are in the merge window at the moment, so net-next is closed at the
> moment. Please repost in two weeks.

Right sorry I only realize this now. I did some reading up on netdev
patches; will make sure to rebase on net-next tree as well when I
submit the v2 in 2 weeks.

> >
> >       /* KSZ87xx Errata DS80000687C.
> >        * Module 2: Link drops with some EEE link partners.
> > @@ -1981,8 +1982,13 @@ static int ksz8_handle_global_errata(struct dsa_switch *ds)
> >        *   KSZ879x/KSZ877x/KSZ876x and some EEE link partners may result in
> >        *   the link dropping.
> >        */
> > -     if (dev->info->ksz87xx_eee_link_erratum)
> > -             ret = ksz8_ind_write8(dev, TABLE_EEE, REG_IND_EEE_GLOB2_HI, 0);
> > +     if (dev->info->ksz87xx_eee_link_erratum) {
> > +             ret = ksz8_ind_write8(dev, TABLE_EEE, REG_IND_EEE_GLOB2_LO, 0);
> > +             if (!ret)
> > +                     ret = ksz8_ind_read8(dev, TABLE_EEE, REG_IND_EEE_GLOB2_LO, &data);
> > +             if (!ret && data)
> > +                     dev_err(dev->dev, "failed to disable EEE next page exchange (erratum)\n");
>
> If data is not 0, should it be considered fatal? Maybe return -EIO ?

Indeed that would make more sense; will return -EIO for v2.

Thanks, Pieter