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How to change RGMII pad characteristics from device tree?

Question asked by Michal Vokac on Jun 8, 2018
Latest reply on Jun 12, 2018 by Michal Vokac

Is there a convenient way to change DDR_SEL and ODT values of the RGMII group of pins without touching the source code? That is from a device tree?

In general to change functions of pins one can easily use the fsl,pins = <PIN_FUNC_ID CONFIG> property.

This is also used to change some bits in the pad configuration register using the CONFIG value.

Unfortunately the DDR_SEL and ODT (among others) register bits in the pad configuration register are read-only and need to be configured using the pad group control registers. How (if at all) can this be done from device tree?

I do not think setting those bits directly from bootloader or from machine platform files is a proper solution. That will be a blocker for upstreaming my board device trees.

My SoC is i.MX6Solo and i.MX6DualLite, RGMII is used to connect a QCA8334 Ethernet switch.


Thanks for any hints.