Re: [PATCH net-next v6] net: phy: intel-xway: Add RGMII internal delay configuration

[Martin Schiller]

On 2023-02-24 09:04, Michael Walle wrote:
> Hi Martin,
>
> Am 2023-02-24 07:25, schrieb Martin Schiller:
> > On 2023-02-22 17:04, Michael Walle wrote:
> > > Hi Tim, Hi Martin,
> > >
> > > > I've got some boards with the GPY111 phy on them and I'm finding 
> > > > that
> > > > modifying XWAY_MDIO_MIICTRL to change the skew has no effect unless 
> > > > I
> > > > do a soft reset (BCMR_RESET) first. I don't see anything in the
> > > > datasheet which specifies this to be the case so I'm interested it
> > > > what you have found. Are you sure adjusting the skews like this
> > > > without a soft (or hard pin based) reset actually works?
> > >
> > > I do have the same PHY and I'm puzzled with the delay settings. Do
> > > you have an EEPROM attached to the PHY? According to my datasheet,
> > > that seems to make a difference. Apparently, only if there is an
> > > EEPROM, you can change the value (the value is then also written to
> > > the EEPROM according the datasheet).
> > > If you don't have one, the values will get overwritten by the
> > > external strappings on a soft reset. Therefore, it seems they cannot
> > > be set. (FWIW there is also a sticky bit, but that doesn't seem to
> > > help in this case).
> > >
> > > -michael
> >
> > Yes, you are right. The datasheet says: "In no-EEPROM mode, writing to
> > this register has no impact on operation of the device".
> >
> > But changing this settings without an EEPROM indeed has an impact.
> >
> > We don't use an EEPROM and without tuning this values some boards are
> > unable to communicate on the ethernet port(s).
>
> Thanks for confirming! Could you share your PHYID1/PHYID2 register and
> firmware version (FWV, 0x1E) contents?

I've 2 PHYs integrated into the VR268 SoC which shows this values:

STD_PHYID1(reg 0x02): 0xd565
STD_PHYID2(reg 0x03): 0xa409
PHY_FWV   (reg 0x1E): 0x8435

And then there are 2 external GPY111 with this values:

STD_PHYID1(reg 0x02): 0xd565
STD_PHYID2(reg 0x03): 0xa401
PHY_FWV   (reg 0x1E): 0x8435

And one external GPY112 with this values:

STD_PHYID1(reg 0x02): 0xd565
STD_PHYID2(reg 0x03): 0xa401
PHY_FWV   (reg 0x1E): 0x8435

> In our case, any changes in MIICTRL are lost after a soft reset.
>
> > I varied these values during operation in the uboot and was able to 
> > test
> > the limits very nicely.
>
> So I guess, the value you write into MIICTRL are retained on a soft 
> reset.

No, the value I write into MIICTRL are not retained on a soft reset.

> I.e.
>
> mii write <phyad> 0x17 0xffff
> mii write <phyad> 0x00 0x8000
> mii read <phyad> 0x17
>
> will still return 0xffff?

In my tests I always set the skew values in register 0x17 first and
then triggered a restart of the ANEG via register 0x0. This then led to
the new values being adopted.

> > I wouldn't have introduced this feature if it hasn't got any impact.
>
> Sure, I'm just trying to figure out the differences ;)
>
> Thanks,
> Michael

- Martin