Messages in this thread | | | Date | Mon, 30 May 2016 09:44:46 +0200 | From | Boris Brezillon <> | Subject | Re: [PATCH 13/15] mtd: nand: samsung: retrieve ECC requirements from extended ID |
| |
Hi Valdis,
On Sun, 29 May 2016 20:20:35 -0400 Valdis.Kletnieks@vt.edu wrote:
> On Fri, 27 May 2016 14:54:59 +0200, Boris Brezillon said: > > From: Hans de Goede <hdegoede@redhat.com> > > > > On some nand controllers with hw-ecc the controller code wants to know > > the ecc strength and size and having these as 0, 0 is not accepted. > > > > Specifying these in devicetree is possible but undesirable as the nand > > may be different in different production runs of the same board, so it > > is better to get this info from the nand id where possible. > > > > This commit adds code to read the ecc strength and size from the nand > > for Samsung extended-id nands. This code is based on the info for the 5th > > id byte in the datasheets for the following Samsung nands: K9GAG08U0E, > > K9GAG08U0F, K9GAG08X0D, K9GBG08U0A, K9GBG08U0B. These all use these bits > > in the exact same way. > > Is this correct for all Samsung nand devices supported by this driver? > > (If this driver only covers those 5 specific parts, it's OK. If there's > others, more research is needed....)
Actually, that was my first reaction [1], but the more I think about it the more I realize it's a non-issue. AFAICT, there's no full-id entries for Samsung NANDs in the nand_ids table, so this either means there's no real users of Samsung MLCs or NAND controller drivers connecting to those chips don't care about the ->ecc_{step_ds,strength_ds} fields.
I agree that the solution is not perfect, but I'd prefer seeing the NAND detection code iteratively improved than rejecting everything until we're 100% sure that all cases are correctly handled (which might never happen since NAND vendors introduce new NAND ID scheme if they need to).
BTW, do you have Samsung datasheets describing a different NAND ID format, or is it purely hypothetical?
Regards,
Boris
[1]http://lists.infradead.org/pipermail/linux-mtd/2015-July/060582.html
-- Boris Brezillon, Free Electrons Embedded Linux and Kernel engineering http://free-electrons.com
| |