Hi, On Friday 28 October 2011 12:30:51 Matthieu CASTET 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. We are doing something similar here as well. Our bootloader also requires the data to be layed out differently (data + ecc interleaved inside a page + oob). > > > 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. Would not it better to add infrastructure for allowing per-partition ECC scheme? This should allow the kernel to also be able to properly handle the bootloader partitions (bad-block scanning ...). > > 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. -- Florian -- 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
