kernel defconfig, CONFIG_MTD_NAND_VERIFY_WRITE

[Christoph Mair]

On Wednesday 06 January 2010 22:02:18 Nelson Castillo wrote:
> On Wed, Oct 6, 2010 at 5:13 PM, Gennady Kupava <gb at bsdmn.com> wrote:
> > В Срд, 06/01/2010 в 13:53 -0500, Nelson Castillo пишет:
> >> On Wed, Oct 6, 2010 at 3:57 PM, Gennady Kupava <gb at bsdmn.com> wrote:
> >> > Hi, patryk
> >> >
> >> > В Срд, 06/01/2010 в 16:16 +0100, Patryk Benderz пишет:
> >> >> Well, if this test was repeated several times with similar results,
> >> >> it might be worth to disable this option IMHO. Only one thing makes
> >> >> me dither. Will this be safe?
> >> >
> >> > I am not 100% sure, as I am not mtd dev, but in other configs have
> >> > this option sometimes disabled. also we have some kind of hw ecc.
> >>
> >> I don't know the details but HW ecc is disabled in the FR.
> >>
> >> static struct s3c2410_platform_nand gta02_nand_info = {
> >>         .tacls          = 0,
> >>         .twrph0         = 25,
> >>         .twrph1         = 15,
> >>         .nr_sets        = ARRAY_SIZE(gta02_nand_sets),
> >>         .sets           = gta02_nand_sets,
> >>         .software_ecc   = 1,
> >> };
> >>
> >> Check drivers/mtd/nand/s3c2410.c if in doubt.
> >
> > First, Paul already committed patch,
> >
> > second,
> >
> > strange, but in config it is enabled:
> > CONFIG_MTD_NAND_S3C2410_HWECC=y
> 
> Check s3c2410.c to see what this option does.
> 
> #ifdef CONFIG_MTD_NAND_S3C2410_HWECC
> static int hardware_ecc = 1;
> #else
> static int hardware_ecc = 0;
> #endif
> 
> 
> AFAIK this is not doing anything in the more OM recent kernels
> (>2.6.31) because the NAND configuration in mach-gta02.c overrides
> this setting.
> 
> See s3c2410.c:
> if (!info->platform->software_ecc && hardware_ecc) {
>  ...
> }
In my 2.6.32 kernel I enabled CONFIG_MTD_NAND_S3C2410_HWECC, set 
.software_ecc=0 and made some speed tests. The Results: 
http://pastebin.ca/1740974
Some operations are slightly faster. I did not observe I/O errors or wrong 
checksums.

Best regards,
  Christoph