On 20.11.2012 16:59, Peter Korsgaard wrote:

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"Daniel" == Daniel Mack [off-list ref] writes:

Hi,

 >>>> In omap2 driver NAND_ECC_HW ecc mode supports 3 ecc layout
 >>>> OMAP_ECC_HAMMING_CODE_HW_ROMCODE
 >>>> OMAP_ECC_BCH4_CODE_HW
 >>>> OMAP_ECC_BCH8_CODE_HW
 >>>> 
 >>>> So selection of ecc layout data should come from DT not ecc mode.
 >>> 
 >>> Ok, I see. I would still like to set them by string rather than magic
 >>> numbers that map to enum entries. Valid values would be "none", "hw",
 >>> "hw-romcode", "bch4" and "bch8". Are you ok with that?
 >> 
 >> Ok, that's nice. Better use ecc_opt instead of ecc_mode.

 Daniel> I did some more extensive tests that include reading the same
 Daniel> nand pages from both U-Boot and the kernel with BCH8 ECC, and
 Daniel> it turns out that -> is_elm_used needs to be set in the pdata
 Daniel> in order to make this work.

So what you're saying is that the choice of ELM or not is not just an
optimization, it really changes the ECC layout? Perhaps it should be
treated as a seperate layout (E.G. bch8-elm) then?

That is what I experienced, yes. The kernel was unable to parse NAND
pages that were written from U-Boot with bch8 hardware mode when the elm
module was not active. Maybe someone from TI can explain that? Giving it
a dedicated name would also solve the problem with the extra DT property.

I'll wait until this is decided before I resend a new set that also
fixes the issue with the errornousely forgotten Documentation file.


Thanks,
Daniel