CONFIG_ASYNC_TX_ENABLE_CHANNEL_SWITCH (not configurable)

configname: CONFIG_ASYNC_TX_ENABLE_CHANNEL_SWITCH

Linux Kernel Configuration
└─>Device Drivers
└─>DMA Engine support
└─>ASYNC_TX_ENABLE_CHANNEL_SWITCH
In linux kernel since version 2.6.37 (release Date: 2011-01-04)  

is selected by
CONFIG_FSL_RAID