CONFIG_MMC_SDHCI_BIG_ENDIAN_32BIT_BYTE_SWAPPER (not configurable)

configname: CONFIG_MMC_SDHCI_BIG_ENDIAN_32BIT_BYTE_SWAPPER

Linux Kernel Configuration
└─>Device Drivers
└─>MMC/SD/SDIO card support
└─>MMC_SDHCI_BIG_ENDIAN_32BIT_BYTE_SWAPPER
In linux kernel since version 2.6.33 (release Date: 2010-02-24)  
This option is selected by drivers running on big endian hosts
and performing I/O to a SDHCI controller through a bus that
implements a hardware byte swapper using a 32-bit datum.
This endian mapping mode is called "data invariance" and
has the effect of scrambling the addresses and formats of data
accessed in sizes other than the datum size.

This is the case for the Freescale eSDHC and Nintendo Wii SDHCI.