In linux-2.6.15-omap1 patch, in arch/arm/mach-omap1/board-osk.c,
EMIFS_CS3_VAL is set to 0x30003361.

This was introduced to fix flash timing error.
http://linux.omap.com/pipermail/linux-omap-open-source/2005-July/004717.html

On the other hand, in SectionE:Errata in EMIFS timing at:
http://omap.spectrumdigital.com/osk5912/osk5912_faq.html
EMIFS_CS3_VAL was set to 0x88013141, fixing write/read rate.

Reading from
http://focus.ti.com/lit/ug/spru742/spru742.pdf
3.6 EMIFS Registers,

0x30003361 will set read mode from "page mode, 4 word/page" to
"asynchronous read", and read from flash slowed down.

I tested with new value 0x88013141, and works good so far.