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iMX6 Dual: Configuring RGMII pins causes SD3 pins to stop working?

Question asked by Josh Watts on Jul 3, 2015
Latest reply on Jul 6, 2015 by Josh Watts

We have a custom board design based on the iMX6 Dual (MCIMX6D6AVT10AD), and I've reached a perplexing issue while trying to bring up the RGMII interface. Configuring any of the following pins causes some of the SD3 pins to no longer function properly:

 

                MX6QDL_PAD_RGMII_TD0__RGMII_TD0      

                MX6QDL_PAD_RGMII_TD1__RGMII_TD1      

                MX6QDL_PAD_RGMII_TD2__RGMII_TD2      

                MX6QDL_PAD_RGMII_RXC__RGMII_RXC      

                MX6QDL_PAD_RGMII_RD3__RGMII_RD3      

                MX6QDL_PAD_RGMII_RX_CTL__RGMII_RX_CTL

 

Since my root filesystem is on an SD card plugged in to SD3, it's much more difficult to debug this issue, although I do have a JTAG probe to read registers if necessary.

 

I've looked through the TRM a fair bit, but the only common thread I can find between the RGMII pins and the SD3 pins is that they originate from the same clock source. Does any one else have any further insight in to what might be causing this?

 

Also, I noticed that the Wandboard Dual uses both these interfaces in pretty much the same exact fashion that I would like, but uses the iMX6 DualLite: Is there any appreciable difference between the SOC I'm using the DualLite?

 

Other details that might be relevant:

  • Linux kernel with only board specific changes based on imx_3.10.17_1.0.0_ga
  • Barebox boot loader based upon v2015.06.0
  • Using 4-bit SDHC on SD3

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