In iMX7D SABRE development board. I'm trying to setup the correct clocking to run the Ethernet from the M4 core. After the DSTREAM debugger connects I see the ENET PLL is already configured correctly. I assume some initial flashed boot loader as done this, however when trying to setting the CCM registers to get correct clocking I find I'm unable to write to these registers to set the root clocks. In particularly trying to get the RGMII TX clock to run at 125MHz. I notices that my phy clock is slight off as well so I suspect the module clock has not been switch to the Ethernet PLL at 125MHz and is running from 120MHz System clock. However setting the ENET1 Reference clock does seem to have any effect on the registers. Do you know what would have prevented access to these registers and what the correct solution would be to setup the ENET controller from the M4 core.