vm-kernel

I use qemu-omap3 to boot linux kernel from nand. The linux image is downloaded from http://beagleboard.googlecode.com/files/uImage_OTG.

OMAP3 beagleboard.org #
OMAP3 beagleboard.org # nand read 0x80000000 0x280000 0x400000
NAND read: device 0 offset 0x280000, size 0x400000
 4194304 bytes read: ERROR
OMAP3 beagleboard.org # bootm 0x80000000
## Booting kernel from Legacy Image at 80000000 ...
   Image Name:   Linux-2.6.22.18-omap3
   Image Type:   ARM Linux Kernel Image (uncompressed)
   Data Size:    1856616 Bytes =  1.8 MB
   Load Address: 80008000
   Entry Point:  80008000
   Verifying Checksum ... Bad Data CRC
ERROR: can't get kernel image!
OMAP3 beagleboard.org #

It means crc error in linux image. I use qemu console command 'memsave' to dump the data from address 0x80000000 to a file and compare it to uImage_OTG. The result is that linux image in ram(from 0x80000000) is different from uImage_OTG. In every block(256 bytes), there is one bit different from uImage_OTG. The linux image is changed when using 'nand read' command to read it from nand flash image to sram.

What has happened when reading linux image from nand flash image into sram??

After debuging about half a day, I find that the data are changed by the correct_data function. I *DID NOT* save ecc value in nand flash image so u-boot thinks the ecc value in oob is wrong and correct it. Ecc can only correct one bit in an block, that is why a bit has been changed in 256 bytes.

ecc_status = this->correct_data(mtd, &data_poi[datidx], &ecc_code[j], &ecc_calc[j]);

I write a file(bb_nandflash_ecc.c) to generate ecc value for nand flash image. Now I can boot linux image using u-boot command.

OMAP3 beagleboard.org # nand read 0x80000000 0x280000 0x400000
NAND read: device 0 offset 0x280000, size 0x400000
 4194304 bytes read: OK
OMAP3 beagleboard.org # bootm 0x80000000
## Booting kernel from Legacy Image at 80000000 ...
   Image Name:   Linux-2.6.22.18-omap3
   Image Type:   ARM Linux Kernel Image (uncompressed)
   Data Size:    1856616 Bytes =  1.8 MB
   Load Address: 80008000
   Entry Point:  80008000
   Verifying Checksum ... OK
   Loading Kernel Image ... OK
OK
Starting kernel ...
smc 80e80414  insn 1600070
Uncompressing Linux.......................................................................................................................... done, booting the kernel.
<5>Linux version 2.6.22.18-omap3 (root@fedoraserver) (gcc version 4.2.1 (CodeSourcery Sourcery G++ Lite 2007q3-51)) #1 Thu Jul 24 15:29:36 IST 2008
CPU: ARMv7 Processor [411fc082] revision 2 (ARMv7), cr=00003837
Machine: OMAP3 Beagle board
Memory policy: ECC disabled, Data cache writeback
<7>On node 0 totalpages: 32768
<7>  DMA zone: 256 pages used for memmap
<7>  DMA zone: 0 pages reserved
<7>  DMA zone: 32512 pages, LIFO batch:7
<7>  Normal zone: 0 pages used for memmap
Unassigned mem readl 4830a204

Because of omap3 emulation is not complete, linux kernel will stop after linux kernel booting. I will work on it.