I just updated U-Boot for my custom BF537 board (similar to the BF537-Stamp) from 2008R2-pre to 2012R1-RC4. I was hoping to see a big improvement in how quickly it reads from the M25P128 SPI flash due to newer versions of U-Boot using DMA . It is some faster, about 1.4MByte/s rather than 0.9MByte/s like before, but not nearly as fast as I hoped for.  suggests that it should be possible to get 3.2MByte/s, which is pretty close to the 3.75MByte/s limit imposed by the 30MHz SPI clock. I am getting less than half of that. Is there an option I need to enable to get DMA assisted transfers?
 - "With latest u-boot (starting SVN revision 1326) there is DMA SPI Flash Read support" https://docs.blackfin.uclinux.org/doku.php?id=fast_boot_example
 - "...this boosts the sequential read speed up to 3.2MByte/s." https://docs.blackfin.uclinux.org/doku.php?id=fast_boot_example