[PATCH v2] ARM: imx: imx8mn-ddr4-evk: Add ethernet support

[Michael Walle]

Hi Marek,

Am 2022-02-21 17:49, schrieb Marek Vasut:
> On 2/21/22 11:10, Michael Walle wrote:
>>> +int board_phy_config(struct phy_device *phydev)
>>> +{
>>> +	/* enable rgmii rxc skew and phy mode select to RGMII copper */
>>> +	phy_write(phydev, MDIO_DEVAD_NONE, 0x1d, 0x1f);
>>> +	phy_write(phydev, MDIO_DEVAD_NONE, 0x1e, 0x8);
>>> +
>>> +	phy_write(phydev, MDIO_DEVAD_NONE, 0x1d, 0x00);
>>> +	phy_write(phydev, MDIO_DEVAD_NONE, 0x1e, 0x82ee);
>>> +	phy_write(phydev, MDIO_DEVAD_NONE, 0x1d, 0x05);
>>> +	phy_write(phydev, MDIO_DEVAD_NONE, 0x1e, 0x100);
>> 
>> This is a AR8031, correct?  Is there a reason why you don't use the
>> device tree binding to set RGMII voltage, and RX and tx delays?
> 
> I quickly cobbled this together from another board, since I needed
> ethernet to do other tests with this board and the ethernet support
> was missing. If you can send subsequent patch to flip this to DT-only
> setup, I can test the patch on the board.

I neither have this board, nor do I care much about it. I just saw
the usual hardcoded atheros phy settings being done in the board
setup. That being said, you can find an example in:
  arch/arm/dts/fsl-ls1028a-kontron-sl28-var4.dts

But you have to figure out what you need. I guess the last four
writes are the rgmii delays which are handled by
   phy-mode = "rgmii-id";

The 0x8 to 0x1f is 1.8V RGMII voltage, you'd need to look at
the schematics if that voltage is actually used. A Zero means
1.5V. If it's using 2.5V then you don't have to do anything
because an external regulator is used.

-michael