[U-Boot] am335x: GPMC: reading speed with prefetch mode

[Yegor Yefremov]

I've got v2015.04-rc4 running on my custom am335x (600MHz) based
board. My 8-bit NAND chip:

[17.297793 0.004021] omap-gpmc 50000000.gpmc: GPMC revision 6.0
[17.303850 0.006057] nand: device found, Manufacturer ID: 0x2c, Chip ID: 0xda
[17.309706 0.005856] nand: Micron MT29F2G08ABAEAWP
[17.312823 0.003117] nand: 256MiB, SLC, page size: 2048, OOB size: 64
[17.317311 0.004488] nand: using OMAP_ECC_BCH8_CODE_HW ECC scheme

I need to load about 17Mb FIT image from UBIFS partition. In Linux it
takes about 7 seconds:

# time cp /mnt/kernel-fit.itb /tmp/
real    0m 7.12s
user    0m 0.00s
sys     0m 6.89s

But U-Boot needs about twice the time:

[3.592231 0.004182] Booting from nand ...
[4.905171 1.312940] UBI: default fastmap pool size: 100
[4.912605 0.007434] UBI: default fastmap WL pool size: 25
[4.919754 0.007149] UBI: attaching mtd1 to ubi0
[5.354450 0.434696] UBI: attached by fastmap
[5.360417 0.005967] UBI: fastmap pool size: 100
[5.365765 0.005348] UBI: fastmap WL pool size: 25
[5.398237 0.032472] UBI: attached mtd1 (name "mtd=5", size 253 MiB) to ubi0
[5.404582 0.006345] UBI: PEB size: 131072 bytes (128 KiB), LEB size:
129024 bytes
[5.409969 0.005387] UBI: min./max. I/O unit sizes: 2048/2048, sub-page size 512
[5.415245 0.005276] UBI: VID header offset: 512 (aligned 512), data offset: 2048
[5.420208 0.004963] UBI: good PEBs: 2029, bad PEBs: 0, corrupted PEBs: 0
[5.424650 0.004442] UBI: user volume: 1, internal volumes: 1, max.
volumes count: 128
[5.430645 0.005995] UBI: max/mean erase counter: 25/18, WL threshold:
4096, image sequence number: 1052535214
[5.438221 0.007576] UBI: available PEBs: 1527, total reserved PEBs:
502, PEBs reserved for bad PEB handling: 40
[5.810683 0.372462] Loading file 'kernel-fit.itb' to addr 0x84000000
with size 17651408 (0x010d56d0)...
[19.013472 13.202789] Done

13 seconds are not affected by CONFIG_NAND_OMAP_GPMC_PREFETCH. Am I
missing some configs?

#ifdef CONFIG_NAND
#define CONFIG_NAND_OMAP_GPMC
#define CONFIG_NAND_OMAP_GPMC_PREFETCH
#define CONFIG_NAND_OMAP_ELM
#define CONFIG_SYS_NAND_5_ADDR_CYCLE
#define CONFIG_SYS_NAND_PAGE_COUNT      (CONFIG_SYS_NAND_BLOCK_SIZE / \
                                         CONFIG_SYS_NAND_PAGE_SIZE)
#define CONFIG_SYS_NAND_PAGE_SIZE       2048
#define CONFIG_SYS_NAND_OOBSIZE         64
#define CONFIG_SYS_NAND_BLOCK_SIZE      (128*1024)
#define CONFIG_SYS_NAND_BAD_BLOCK_POS   NAND_LARGE_BADBLOCK_POS
#define CONFIG_SYS_NAND_ECCPOS          { 2, 3, 4, 5, 6, 7, 8, 9, \
                                         10, 11, 12, 13, 14, 15, 16, 17, \
                                         18, 19, 20, 21, 22, 23, 24, 25, \
                                         26, 27, 28, 29, 30, 31, 32, 33, \
                                         34, 35, 36, 37, 38, 39, 40, 41, \
                                         42, 43, 44, 45, 46, 47, 48, 49, \
                                         50, 51, 52, 53, 54, 55, 56, 57, }

#define CONFIG_SYS_NAND_ECCSIZE         512
#define CONFIG_SYS_NAND_ECCBYTES        14
#define CONFIG_SYS_NAND_ONFI_DETECTION
#define CONFIG_NAND_OMAP_ECCSCHEME      OMAP_ECC_BCH8_CODE_HW
#define CONFIG_SYS_NAND_U_BOOT_START    CONFIG_SYS_TEXT_BASE
#define CONFIG_SYS_NAND_U_BOOT_OFFS     0x00080000
#endif
#endif

Yegor