I have built u-boot with different parameters in the .config file for several LCD panels: 800x480 and 800x600. That becomes the size of the reported uboot screen and also the Linux kernel inherits the same size. But always 32 bit, even if I put the depth=16 rather than the standard depth=18 into the configuration.
My problem is not with the memory allocated internally for the FB: it's the application in the user space that needs many off the screen windows (pixel buffers, really) that have to match the ARGB FB format.
Anybody?