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When the frequency on the nand chip pins is above 33MHz, the nand EDO(extended Data Out) timing could be applied. The GPMI implements a Feedback read strobe to sample the read data in the EDO timing mode. This patch adds the EDO feature for the gpmi-nand driver. For some onfi nand chips, the mode 4 is the fastest; while for other onfi nand chips, the mode 5 is the fastest. This patch only adds the support for the fastest asynchronous timing mode. So this patch only supports the mode 4 and mode 5. I tested several Micron's ONFI nand chips with EDO enabled, take Micron MT29F32G08MAA for example (in mode 5, 100MHz): 1) The test result BEFORE we add the EDO feature: ================================================= mtd_speedtest: MTD device: 2 mtd_speedtest: MTD device size 209715200, eraseblock size 524288, page size 4096, count of eraseblocks 400, pages per eraseblock 128, OOB size 218 ....................................... mtd_speedtest: testing eraseblock read speed mtd_speedtest: eraseblock read speed is 3632 KiB/s ....................................... mtd_speedtest: testing page read speed mtd_speedtest: page read speed is 3554 KiB/s ....................................... mtd_speedtest: testing 2 page read speed mtd_speedtest: 2 page read speed is 3592 KiB/s ....................................... ================================================= 2) The test result AFTER we add the EDO feature: ================================================= mtd_speedtest: MTD device: 2 mtd_speedtest: MTD device size 209715200, eraseblock size 524288, page size 4096, count of eraseblocks 400, pages per eraseblock 128, OOB size 218 ....................................... mtd_speedtest: testing eraseblock read speed mtd_speedtest: eraseblock read speed is 19555 KiB/s ....................................... mtd_speedtest: testing page read speed mtd_speedtest: page read speed is 17319 KiB/s ....................................... mtd_speedtest: testing 2 page read speed mtd_speedtest: 2 page read speed is 18339 KiB/s ....................................... ================================================= 3) The read data performance is much improved by more then 5 times. Signed-off-by: Huang Shijie <b32955@freescale.com> Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com> Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>