AnsweredAssumed Answered

SPI flash read speed not as fast as expected

Question asked by skstrobel on Oct 5, 2012
Latest reply on Oct 15, 2012 by skstrobel

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 [1].  It is some faster, about 1.4MByte/s rather than 0.9MByte/s like before, but not nearly as fast as I hoped for.  [2] 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?




[1] - "With latest u-boot (starting SVN revision 1326) there is DMA SPI Flash Read support"


[2] - "...this boosts the sequential read speed up to 3.2MByte/s."