Re: [PATCH net v1 1/1] net: dsa: microchip: don't try do read Gbit registers on non Gbit chips

[Oleksij Rempel <o.rempel@pengutronix.de>]

On Thu, Jul 28, 2022 at 03:25:35PM +0200, Andrew Lunn wrote:
> On Thu, Jul 28, 2022 at 03:17:25PM +0200, Oleksij Rempel wrote:
> > Do not try to read not existing or wrong register on chips without
> > GBIT_SUPPORT.
> > 
> > Fixes: c2e866911e25 ("net: dsa: microchip: break KSZ9477 DSA driver into two files")
> > Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
> > ---
> >  drivers/net/dsa/microchip/ksz9477.c | 8 +++++++-
> >  1 file changed, 7 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/net/dsa/microchip/ksz9477.c b/drivers/net/dsa/microchip/ksz9477.c
> > index c73bb6d383ad..f6bbd9646c85 100644
> > --- a/drivers/net/dsa/microchip/ksz9477.c
> > +++ b/drivers/net/dsa/microchip/ksz9477.c
> > @@ -316,7 +316,13 @@ void ksz9477_r_phy(struct ksz_device *dev, u16 addr, u16 reg, u16 *data)
> >  			break;
> >  		}
> >  	} else {
> > -		ksz_pread16(dev, addr, 0x100 + (reg << 1), &val);
> > +		/* No gigabit support.  Do not read wrong registers. */
> > +		if (!(dev->features & GBIT_SUPPORT) &&
> > +		    (reg == MII_CTRL1000 || reg == MII_ESTATUS ||
> > +		     reg == MII_STAT1000))
> 
> Does this actually happen?

Yes. I just discovered it after adding regmap ranges validation for
KSZ9893 chip.
> 
> If i remember this code correctly, it tries to make the oddly looking
> PHY look like a normal PHY. phylib is then used to drive the PHY?
> 
> If i have that correct, why is phylib trying to read these registers?
> It should know there is no 1G support, and should skip them.

I didn't investigated it so far. Will try to look deeper tomorrow.

Regards,
Oleksij
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