Broken ethernet on SolidRun cubox-i

[Michael Walle]

Am 2021-01-08 12:53, schrieb Russell King - ARM Linux admin:
> 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?

I don't have a cubox. But it's just a device tree patch. I could
try to hack one based on Christophs dtb and he could just replace
it on his sd card and test. Seems easy enough.

-- 
-michael