Current our design only 1.8V supply to NVCC_SDx pin.
it means that we do not change IO voltage response to access speed changing.
Is it okay for SD host controller in i.MX6?
Because, SDIO specification v3.0 mentioned as below.
1.2.3 Embedded SDIO Device Features
・Supply Voltage rage：2.7-3.6V or 1.7-1.95V