The chip select lines of the iMX SPI module doesn't work well for a
generic API like the one RTEMS uses. The existing solution only worked
in some special cases and had odd bugs when trying transfers of
different sizes (like deselecting between each byte for lengths that are
not dividable by 4).
With this patch the same approach like on FreeBSD or Linux is used:
Treat the CS lines as GPIOs.
Update 3869
