I am trying to build angstrom kernel, with only dss2 driver replaced
with a custom frame buffer driver. I am using bootargs as:

setenv bootargs console=ttyS2,115200n8 root=/dev/mmcblk0p2 noinitrd rw
rootdelay=2 rootfstype=ext3 mpurate=600 buddy=unknown omapfb.vram=0:4M,
1:4M omapfb.mode=dvi:1024x768MR-16@60  omapdss.def_disp=dvi

and i am getting error from, dma_alloc_coherent, when i try to use
more than one frame buffers.

When i got this error in vmlinux kernel, increasing,  device driver->
graphics support -> Consistent DMA memory size in menuconfig, helped
me to solve that error, now in angstrom, i did not find exactly the
same option in menuconfig. Does this option exist?

as i did not find Consistent DMA memory size option in angstrom
kernel's menuconfig , I increased, VRAM size in Device Drivers-
>Graphics support ->OMAP2/3 Display Subsystem support, to 32MB from
14MB, but that did not solve dma_alloc_coherent failure for me.  Any
suggestions about solving this error?