Dear chris c,
In message AANLkTi=usuEyf4YuUVWrrLu80bMRFpRF+BThEix2bFNg@mail.gmail.com you wrote:
I was comparing time just by timing it manually. How did you instrument u-boot to display the time?
That's no instrumentation of U-Boot, but just timestamping the output on the serial console. See for example ftp://ftp.denx.de/pub/tools/time_log
As for the small versus large file, I did the same test for 1MB of data using nand read and saw a x4 performance advantage. I also did a test on mmc with 100 MB file and saw no performance increase. Looks like file size doesn't matter.
So does that mean that MMC file loading will not benefit from dcache enabled? Can anybody explain this?
It depends on where the time is actually spent. If you have a slow (say, bit-banging) MMC driver and a low-performance CPU then the transfer from MMC might simply not depend as much on caches. It is wrong to check just a simple use case. Try a number of different operations, like umcompressing a large image in RAM or from NOR to RAM, or downloading over the net, or ...
Best regards,
Wolfgang Denk