[U-Boot] OMAP3 broken NAND hardware ECC generation

[U-Boot] OMAP3 broken NAND hardware ECC generation

[Dirk Behme]

Dear Scott and Nishanth,

we have broken OMAP3 NAND hardware ECC generation while our clean up 
of OMAP3 NAND code.

I did some debugging. Do you like to have a look to

http://git.denx.de/?p=u-boot/u-boot-arm.git;a=blob;f=drivers/mtd/nand/omap_gpmc.c;h=01b79593949fe828e4b1d3da2cf4b399c1b580ab;hb=refs/heads/omap3

?

Using some well defined data in SDRAM, I used older U-Boot with 
working nand ecc hw/sw implementation and our recent version to write 
this data to NAND. I then compared ecc written and found that our 
latest version writes the correct location, but all zero:

Working version from older U-Boot:

OOB:
         ff ff ec 13 0f 00 00 00
         00 00 00 00 00 00 ff ff
         ff ff ff ff ff ff ff ff
         ff ff ff ff ff ff ff ff
         ff ff ff ff ff ff ff ff
         ff ff ff ff ff ff ff ff
         ff ff ff ff ff ff ff ff
         ff ff ff ff ff ff ff ff

Recent version:

OOB:
         ff ff 00 00 00 00 00 00
         00 00 00 00 00 00 ff ff
         ff ff ff ff ff ff ff ff
         ff ff ff ff ff ff ff ff
         ff ff ff ff ff ff ff ff
         ff ff ff ff ff ff ff ff
         ff ff ff ff ff ff ff ff
         ff ff ff ff ff ff ff ff

In both versions the data the ecc is calculated for is the same. In 
recent version only zero is written.

Some additional debugging by adding some printf() in hw ecc functions:

OMAP3 beagleboard.org # nandecc hw
omap_hwecc_init
HW ECC selected
OMAP3 beagleboard.org # nand write 80000000 680000 1000

NAND write: device 0 offset 0x680000, size 0x1000
omap_calculate_ecc 0x00 0x00 0x00
omap_calculate_ecc 0x00 0x00 0x00
omap_calculate_ecc 0x00 0x00 0x00
omap_calculate_ecc 0x00 0x00 0x00
omap_calculate_ecc 0x00 0x00 0x00
omap_calculate_ecc 0x00 0x00 0x00
omap_calculate_ecc 0x00 0x00 0x00
omap_calculate_ecc 0x00 0x00 0x00
  4096 bytes written: OK
OMAP3 beagleboard.org #

This is the result of

printf("omap_calculate_ecc 0x%02x 0x%02x 0x%02x\n", ecc_code[2], 
ecc_code[1], ecc_code[0]);

I'm not sure, but it seems to me, that omap_enable_hwecc() is never 
called. An printf() in this function is not shown.

Maybe call of nand_scan_tail(mtd); in omap_nand_switch_ecc() resets 
anything? Or any other idea?

Thanks for your help

Dirk

[U-Boot] OMAP3 broken NAND hardware ECC generation

[Scott Wood]

Dirk Behme wrote:
> I'm not sure, but it seems to me, that omap_enable_hwecc() is never 
> called. An printf() in this function is not shown.
> 
> Maybe call of nand_scan_tail(mtd); in omap_nand_switch_ecc() resets 
> anything? Or any other idea?

You never cleared out nand->ecc.write_page (and others), so 
nand_scan_tail() saw that they were non-NULL and assumed you were 
overriding them, and you got the soft-ECC versions of those, but the 
hard-ECC calculate method.

-Scott