Hi Avinash, Hi Peter, On 23.11.2012 11:43, Philip, Avinash wrote: > On Wed, Nov 21, 2012 at 15:45:23, Daniel Mack wrote: >> On 20.11.2012 16:59, Peter Korsgaard wrote: >>>>>>>> "Daniel" == Daniel Mack <zonque@xxxxxxxxx> writes: > Peter, > > In patch [1], mtd: nand: omap2: Support for hardware BCH > > ecc_layout made compatible with Rom Boot Loader ECC layout for am335x. > > This action is based on is_elm_used flag. > > Requirement of this flag is to identify the whether the platform > ELM module & based on this configure ELM module if present. > > But ideally BCH8 ecc lay out didn't have a dependency on ELM, it > can work with software BCH ecc. RBL compatibility is missing > in software BCH because of addition of constant polynomial to > ecc vector. If we remove the dependency on erased page handling > by ecc vector with constant polynomial, software BCH can do the > job of RBL compatibility. > > Ivan, > Do you have any suggestions? > Discussion for RBL compatibility found at [2]. > > It is good that software BCH also support RBL compatibility by suppressing > constant polynomial modification. Then ecc layout can be selected from > DT entry and error correction can be chosen between software/hardware > depending on the availability of ELM hardware. > Currently RBL BCH8 compatibility depends on the availability of ELM > hardware. Later once software BCH start supporting RBL compatibility, > we can remove the check. > >> >> 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. > > Daniel, > > Currently BCH8 is supported with software ecc error correction in mainline. > The layout for BCH8 ECC layout is > 0-1 -> BAD block markers > 2-11-> oob free area > 12-63-> BCH8 ECC. > > RBL ECC layout is > 0-1 -> BAD block markers > 2-57-> BCH8 ecc layout > 58-63-> OOB free area > > As u-boot also maintain RBL ecc layout, write from U-boot > and read from Linux requires compatibility with RBL ecc layout. > The same is achieved in the patch [1], with by setting is_elm_used > to true. > > 1. https://lkml.org/lkml/2012/10/31/87 > 2. https://lkml.org/lkml/2012/10/11/20 So, after reading this, I'm still uncertain what's your preferred way of handling the bindings here. Are you saying we should stick with the is_elm_used flag, and subsequently care for BCH8 software mode compatibility? I would like to submit a new version soon, so it can be queued up for the next merge window, and that decision is the last blocker currently for sending out a new series. Many thanks, Daniel -- 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
