On Friday 19 November 2010 03:33:24 Ghorai, Sukumar wrote: > > -----Original Message----- > > From: linux-omap-owner@xxxxxxxxxxxxxxx [mailto:linux-omap- > > owner@xxxxxxxxxxxxxxx] On Behalf Of Charles Manning > > Sent: Thursday, November 18, 2010 6:36 AM > > To: linux-omap@xxxxxxxxxxxxxxx > > Subject: No more software ECC in omap2.c NAND driver. Why? > > > > Between 2.6.35 and 2.6.36 there have need quite a few changes in the NAND > > driver, including a change from software to hardware ECC. > > > > The new code has hardware ECC forced on by: > > > > #define CONFIG_MTD_NAND_OMAP_HWECC > > > > I am surprised that this was done. Surely this should have been a Kconfig > > option to select either sw ECC or hw ECC? > > > > Does moving to hardware ECC to the exclusion of software ECC reduce > > functionality? > > [Ghorai] This is wrongly added by me, during last few patches. So I have > send the fix as you mentioned too as. > [PATCH] omap: nand: remove hardware ECC as default > > And please let me know still if it has any issue. Just recompiling with the CONFIG_MTD_NAND_OMAP_HWECC define commented out did not result in a working system. I suspect there is more tto the problem than this. > > And I am re-working on the patches for the different ecc schema including > s/w, h/w or different, to pass it form board file. > > > Does the new hwecc scheme still support sub-page writes or does it only > > provide full page writes? If sub-page writes are lost then this has a > > ripple > > effect in breaking the way some UBI stuff works. > > [Ghorai] > 1. do you think this sub-page read/write support was there before, say in > 2.6.35? And breaks in 2.6.36? 2.6.35 works with subpages of 512 bytes. Tested with UBIFS. > > 2. In that case would you please let know what are the size(s) used for > sub-page/read write? AFAIK, 512 is all that is needed. There is no need for any smaller or larger. sub-page reads are not available on all flash types and sub-page writing causes extra write disturb. However, 512-byte sub-page writing is valuable. This of course needs the ECC to be partitioned and performed in chunks of 256 or 512 so that the subpages can be written individually. -- CHarles -- 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
