Hi,
I spent some time looking into boot times of AM335x platforms. One big improvement I made came with adding support for GPMC prefetch mode, which gave a speed-up of NAND reads of roughly factor 2. This is what patch #1 does.
Note that this is currently limited to read operations in 8-bit mode, but I believe it could be easily extended to 16-bit operations if anyone has hardware to test it on. Using the engine for write mode speed improvements should also be doable, but I didn't spend time on it yet. That can be added as a separate patch later.
Patch #2 decreases the GPMC memory map window size from 256MiB to 16MiB. Admittedly, I'm not quite sure about the reason, but a read from offset 0 in this memory area will freeze U-Boot instantly if the size is configured to 256MiB. As contents of the FIFO are accessed in a pseudo-mode from offset 0 anyway, it doesn't really matter.
What I also did to further speed up my boot was to tweak the GPMC parameters for the NAND chip on our boards, but that's not part of this patch set, and probably deserves a little more cleanup.
Test results and feedback very welcome.
Thanks, Daniel
Daniel Mack (2): mtd: OMAP: Enable GPMC prefetch mode ARM: omap-common: gpmp: decrease memory region size to 16MiB
arch/arm/cpu/armv7/omap-common/mem-common.c | 2 +- doc/README.nand | 5 ++ drivers/mtd/nand/omap_gpmc.c | 115 +++++++++++++++++++++++++++- include/linux/mtd/omap_gpmc.h | 6 +- 4 files changed, 124 insertions(+), 4 deletions(-)