NAND/ MTD is very slow in kernel 2.6.35.9

Hi

I have just upgraded the linux kernel for daVinci DM6467 from 2.6.23 to 2.6.35.9 (from kernel.org). The board is booting now, but all access to NAND are slow. The NAND is 1Gbyte and scanning for bad blocks takes about 1 minute. I have both NOR and NAND on this board, booting from NOR. Both U-boot and the old kernel scans the same NAND in a much shorter time.

OProfile give me the below, when copy a file from NAND to /dev/null:

CPU: CPU with timer interrupt, speed 0 MHz (estimated)

Profiling through timer interrupt

samples  %        app name                 symbol name

33       19.4118  vmlinux                  cfi_qry_mode_on

32       18.8235  bash                     /bin/bash

31       18.2353  vmlinux                  mtd_unlocked_ioctl