On Fri, Oct 28, 2011 at 12:30 PM, Matthieu CASTET <matthieu.castet@xxxxxxxxxx> wrote: > Hi, > > Javier Martinez Canillas a écrit : >> Hello, >> >> I want to be able to use 1-bit ECC for the first partition where I >> save the loader binary and has to be accessed by the ROM boot but use >> a 4-bit ECC for my rootfs partition. >> >> Does anyone have this same issue? > We use raw programming and compute the ecc in software. > > Hi Matthieu, We also thought that solution but it wasn't clear for me if doing a RAW write to the mtd device I skip the NAND driver and could also write the oob section without that value being recalculate and rewrite by the driver. >> >> What is the best approach to store data in a NAND device using >> different ECC techniques? >> >> I've think of two approaches: >> >> 1- Adding an ioctl to mtdchar (something like ECCSETBITS) to change >> the ECC technique used. > But this won't work if there is concurrent acess to mtd. One program may want 1 > bit ecc other want 4 bits ecc. > >> 2- Use a platform data field to notify the omap2 nand driver that the >> ROM boot only supports 1-bit ECC. So it can use a 1-bit ECC to write >> and read the first 4 sectors but a 4-bit ECC for the rest. > This may be better. > > Matthieu > > PS : note that some OMAP ROM support a better protection than Hamming (but the > details are not public AFAIK) > > From OMAP34xx Multimedia Device, Silicon Revision 3.1.x, public version : > > Pages can contain errors caused by memory alteration. To correct these errors, > the ROM code uses ECC, > based on Hamming codes for SLC NAND and BCH (Bose, Ray-Chaudhuri, Hocquenghem) > code for > multilevel cell (MLC) devices. The computed ECC is compared to ECC stored in the > spare area of the > corresponding page. If there are uncorrectable errors, the ROM code returns with > FAIL. > Yes I've read that on the DM3730 TRM but as far as I understand only applies to MLC devices, but ours is SLC. Thank you and best regards, -- Javier Martínez Canillas (+34) 682 39 81 69 Barcelona, Spain -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
