CONFIG_BFIN_EXTMEM_DCACHEABLE is not available for thedefaultarchitecture x86.
Result is shown for architecture blackfin
default or selected kernelversion does not have config value CONFIG_BFIN_EXTMEM_DCACHEABLE.
Result is shown for kernelversion 6.7-rc3

Enable DCACHE for external memory

configname: CONFIG_BFIN_EXTMEM_DCACHEABLE

Linux Kernel Configuration
└─>Blackfin Processor Options
└─>Enable DCACHE for external memory
In linux kernel since version 2.6.31 (release Date: 2009-09-09)