IMX.6 ENET clock and KSZ8775CLXIC switch

[maciejskrzypek]

We have connected KSZ8775CLXIC using RGMII interface to IMX.6. It did not work because as it turns out IMX.6 needs reference clock connected to ENET_REF_CLK which we did not connect. This switch does not have 125MHz reference clock output. We can use internal clock from IMX6 but it needs to be routed externally from GPIO_16 to ENET_REF_CLK, but KSZ8775CLXIC does not support 125MHz clock input We currently have connected ENET_REF_CLK to RXC (only for testing) output pin on switch and it does work but only on 1Gbit speed when RXC is 125MHz. We are not sure if clocking IMX Enet interface from internal source (GPIO_16) will work (we cannot test it on current hardware revision) and switch clocked independently on all speeds 1G/100M/10M?

Or maybe it is better to use clock multiplier on switch 25MHz clock output?

[igorpadykov]

Hi Maciej

if PHY can't provide 125M clock, recommended to connect GPIO_16 to ENET_CLK_REF  

please look at example on

https://community.freescale.com/message/425432#425432

Best regards

igor

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[maciejskrzypek]

So it is ok if IMX and switch are clocked from independent clocks, even on all speed settings?

[igorpadykov]

I believe such option is also possible.

~igor