SDMMC

The QB EMMC driver can be configured and instanced using the sdmmc node. For example:

sdmmc {
    /* Instance numbering starts from 0 */
    sdmmc@3 {
        Instance = <3>;
        /*
         * 2 - skip CMD0, start full init with CMD1
         * 1 - init only, exit after CMD0 and initiating CMD1
         * 0 - full initialization
         */
        InitTypeNative = <0>;
        InitTypePL = <0>;
        InitTypeOSL = <0>;
        factor =
            /* ClockDivisor, CardClockDivisor, Mantissa */
            <4 2 1>;
            DataWidth = <6>;
            DisableHS400 = <1>;
            /* Values depend on SDR or DDR mode selection */
            TapVal = <0x9>;
            TrimVal = <0x5>;
    };
};

Where:

• Instance is the controller instance in hardware: 0, 1, or 2, as explained in the example's comments.
• factor is the internal controller clock divisor setting <ClockDivisor, CardClockDivisor, Mantissa>.
• DisableHS400 is set to 1 for EMMC in DDR 50, or 0 for EMMC in HS400 (if supported by the device).
• TapVal and Trim Val are fixed values based on SDR/DDR mode. They should not be changed.

The SDMMC driver is shared by several stage bootloaders (Quickboot, Partition Loader, and OS Loader).

The InitTypeNative, InitTypeFL, and InitTypeOSL fields allow further initialization time optimization in SDMMC node. These nodes are:

InitTypeNative = <0>;
InitTypePL = <0>;
InitTypeOSL = <0>;

For each field:

• 0 specifies full initialization.
• 1 abbreviates initialization: the process ends after sending CMD0 and initiating CMD1.
• 2 skips CMD0 and starts full initialization with CMD1.