i.mx8mp ENET RGMII 3.3V worked

[WALNUTY]

Hi,

We want to use RGMII on i.mx8mp, but the ENET uses 3.3V. Could it work?

I tested 3.3V on ENET and found RGMII worked. However, in datasheet, RGMII requestes 1.8V only. 

Could you give advice if it riskly, like stability?

BR.

Hunt Yang

[weidong_sun · Accepted solution]

Dear @WALNUTY ,

See the following screeshot, which is from i.MX8MP datasheet.

NVCC_ENET & NVCC_SAI1_SAI5 can be suppied by 3.3V.

So for Ethernet IO, 3.3V power is no problem.

>>Could you give advice if it riskly, like stability?

Most of gigabit Phy products supports 1.8V / 2.5V IO, it is easy to buy from current market. Actually ethernet phy with 3.3V can also be got, but few kinds of the products. I have ever used KSZ9031, which supports 3.3V IO, you can check it.

Thanks!

Regards,

weidong

[anhira]

Hi Weidong, 

I have a custom board with the iMX8MP processor. This processor is connected via RGMII to the 88LX5153 (G.hn Digital Chip MxL), which can configure its controller as either MAC or PHY.

In this case, it's set up as PHY to connect it to the iMX8MP. However, its voltage for the RGMII is 2.5V. In the design, I connected the NVCC_SAI1_SAI5 pin to 2.5V. Is this correct? Can it function properly at this voltage without issues? Should I consider anything else? Perhaps in boot strapping or DTB configuration?

The design is based on the iMX8MP-EVK evaluation board. Right now, the eth0 interface isn't coming up. During boot, these messages appear:

Net: Could not get PHY for FEC0: addr 1 Could not get PHY for FEC0: addr 1

[ 2.966142] mdio_bus 30be0000.ethernet-1: MDIO device at address 1 is missing.

[ 2.974045] fec 30be0000.ethernet eth0: registered PHC device 0

Can you help me try to solve this problem?
Thank you.

Toni.