I am debugging flash driver for MPC8555CDS board. The driver is drivers/cfi_flash.c. I have two boards. One is rev 1.0, with AM29LV641D. The other is rev 1.1, with AM29LV641M.
The problem is polling DQ6 after programming. The current driver in U-boot 1.1.2 works well for AM29LV641M. As for AM29LV641D, the programming hangs after writing about 13KB. I track it down to "flash_is_busy()" function. When the problem occurs, the DQ6 keeps toggling. If I change the algorithm to polling DQ7, no problem occurs.
Shawn has a similar problem http://lists.infradead.org/pipermail/linux-mtd/2004-March/009402.html. Maybe we should use DQ7 rather than DQ6.
Another issue is the CFI driver might not work for all CFI compatible flash. For example, Micro MT28F640J3. Micro uses status register instead of DQ# polling. Somehow, we still need board specific driver.