On Sun, Dec 27, 2020 at 04:11:14PM +0000, Russell King - ARM Linux admin wrote:
> On Sun, Dec 27, 2020 at 04:59:39PM +0100, Michael Walle wrote:
> > Am 2020-12-27 16:33, schrieb Michael Walle:
> > > Am 2020-12-26 13:34, schrieb Russell King - ARM Linux admin:
> > > > I'd forgotten that there were boards out there with this problem...
> > > > the PHY address configuration is done via the LED_ACT pin, and
> > > > SolidRun
> > > > omitted a pull resistor on it, so it "floats" with the leakage current
> > > > of the LED/pin - resulting in it sometimes appearing at address 0 and
> > > > sometimes at address 4.
> > > 
> > > Mh, I've guessed that too, but there must be more to it. The datasheet
> > > says it has an internal weak pull-up. Or Atheros messed up and it
> > > doesn't
> > > reliably work if there is actually an LED attached to it. But then, why
> > > would any other stronger pull-up/down work..
> > 
> > Mhh, nevermind, from the commit log [1].
> > 
> >   "The LED_ACT pin on the carrier-one boards had a pull down that
> >   forces the phy address to 0x0; where on CuBox-i and the production
> >   HummingBoard that pin is connected directly to LED that depending
> >   on the pull down strength of the LED it might be sampled as '0' or '1'
> > thus
> >   the phy address might appear as either address 0x0 or 0x4."
> > 
> > So it actually depends on the forward voltage of the LED and the
> > hi/low thresholds of the AT8035.. nice! Oh and btw. this pin also
> > switches between high and low-active LED output. So the missing
> > pull-down might not only switch the PHY address to 4 but also invert
> > the LED state.
> 
> Indeed. And whether it appears at address 0 or 4 will depend on many
> factors, including temperature - LEDs have a decrease of 2mV/°C.
> 
> I wonder if we can just delete the phy-handle property, and list a
> PHY at both address 0 and 4 with the appropriate configuration...

Michael, can you try the attached patch please?

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