[PATCH] net: bcmgenet: Don't set ID_MODE_DIS when not using RGMII

[Nicolas Saenz Julienne]

Hi Matthias,

On Thu, 2020-02-20 at 19:58 +0100, Matthias Brugger wrote:
> 
> On 20/02/2020 17:36, Nicolas Saenz Julienne wrote:
> > As per Linux's driver, ID_MODE_DIS is only set when the PHY interface is
> > RGMII. Don't enable it for the rest of setups.
> > 
> > This has been seen to misconfigure RPi4's PHY when booting Linux.
> > 
> > Signed-off-by: Nicolas Saenz Julienne <nsaenzjulienne at suse.de>
> > ---
> >  drivers/net/bcmgenet.c | 5 ++++-
> >  1 file changed, 4 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/net/bcmgenet.c b/drivers/net/bcmgenet.c
> > index 8f4848aec6..e971b556ac 100644
> > --- a/drivers/net/bcmgenet.c
> > +++ b/drivers/net/bcmgenet.c
> > @@ -448,7 +448,10 @@ static int bcmgenet_adjust_link(struct
> > bcmgenet_eth_priv *priv)
> >  	}
> >  
> >  	clrsetbits_32(priv->mac_reg + EXT_RGMII_OOB_CTRL, OOB_DISABLE,
> > -			RGMII_LINK | RGMII_MODE_EN | ID_MODE_DIS);
> > +			RGMII_LINK | RGMII_MODE_EN);
> > +
> > +	if (phy_dev->interface == PHY_INTERFACE_MODE_RGMII)
> > +		setbits_32(priv->mac_reg + EXT_RGMII_OOB_CTRL, ID_MODE_DIS);
> 
> Is this given because by different DTS? Shouldn't that be uniform on the RPi4?

The interface type is read from DT, the 'phy-mode' property. In the case of the
RPi4 it's 'rgmii-rxid'.

The downstream DT used to be configured differently ('rgmii' and using
'ethernet-phy-ieee802.3-c22'), that's why you might have seen the board working
at some point with this driver. But as we updated the DT to match upstream's we
switched to 'rgmii-rxid' which is being misconfigured as 'rgmii' in u-boot. So
you have u-boot configuring 'rgmii' while Linux configures 'rgmii-rxid', which
fails to clear the ID_MODE_DIS bit. This, I imagine, blocks the delay
configuration process from the PHY (I don't have any documentation).

Regards,
Nicolas

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