Due to a typo in the fsl_mmc middleware driver, 4 bit transfers are very slow as the driver fails to properly select 4 bit mode. Fixed in: https://github.com/nxp-mcuxpresso/mcuxsdk-middleware-sdmmc/pull/4 @yangbolu1991 as it seems you're the maintainer of this driver, please have a look.
Due to a typo in the fsl_mmc middleware driver, 4 bit transfers are very slow as the driver fails to properly select 4 bit mode.
Fixed in: #4
@yangbolu1991 as it seems you're the maintainer of this driver, please have a look.