On Thu, Mar 28, 2013 at 10:23:01PM +0000, Aaron Williams wrote: > Hi all, > > I am trying to clean up our OCTEON NAND flash driver in the Linux kernel > and enable support for multi-bit ECC using BCH and am having some > issues. I am able to successfully work with NAND flash that requires 4 > bits ECC per 512 bytes but I am having issues with one of our boards > that has a NAND device that requires 24 bits of ECC per 1024 bytes. > > I was wondering if ECC of this magnitude has been successfully tested in > the past. By my calculations I should have 42 bytes of ECC per 1K block > (m=14, t=24 for 336 bits of ECC data). My problem is that when decoding > an encoded block I am seeing that nroots != err in decode_bch() after > find_poly_roots(). I am seeing this for all of the blocks I attempt to > read. As far as I can tell the data being sent to BCH is good, though it > might have a few bad bits but nowhere near 24. > > I am also seeing this same behavior in my U-Boot code which uses the > identical bch and nand_bch code. >
Hi Aaron, CC-ing your message to linux-mtd which is the place to go for such questions :-) Your configuration (m=14 t=24 with 1024 bytes of data) has been tested, and should work with the BCH library. Could you give some details about your ECC setup: 1. Are you trying to locate and correct errors from hardware-computed syndromes ? 2. If yes, did you provide the BCH lib with the specific primitive polynomial used by your hardware ? What is this polynomial ? 3. Could you provide the ECC bytes generated for the following block patterns: - a 0xff-filled 1024 bytes block - a 0xff-filled 1024 bytes block, except for the first byte set to 0xfe This would help me find out how to setup the library to match your hardware. Regards, -- Ivan -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
