default or selected kernelversion does not have config value CONFIG_SERIAL_BFIN_PIO.
Result is shown for kernelversion 6.7-rc3
PIO mode
configname: CONFIG_SERIAL_BFIN_PIO
UART Mode
└─>PIO mode
In linux kernel since version 2.6.24 (release Date: 2008-01-24)
This driver works under PIO mode.