gpmi-nand ecc

[Miquel Raynal]

Hi Sean,

+ u-boot ML

Sean Nyekjaer <sean at geanix.com> wrote on Wed, 14 Apr 2021 15:13:39
+0200:

> Hi,
> 
> I have two boards with a iMX6ULL SoC one attached to a Micron NAND flash (MT29F4G08ABAFAWP) and one a Toshiba (TC58BVG2S0HTAI0).
> 
> After updating the boards from u-boot 2018.07 -> 2020.01, the Micron fitted boards is having ECC problems(in u-boot).
> U-boot 2018.07 selects ecc_strength to 18.
> U-boot 2020.01 selects ecc_strength to 8, but if I hardcode u-boot to run the mxs_nand_legacy_calc_ecc_layout() it selects 18 bits.
> 
> The Toshiba boards always selects 8 bit ecc_strength so they have no issues.
> 
> The kernel driver (gpmi-nand.c) seems to also use the legacy method (Resulting 18 bits in ecc strength for the Micron NAND).
> In common_nfc_set_geometry(): Both chip->ecc.strength and chip->ecc.size are 0.
> 
> I would expect ecc.strength to be set to 8, earlier but cannot find the spot where it should be set.
> Is the gpmi-nand driver missing a call to nand_ecc_choose_conf()?
> Maybe we need a legacy option for the kernel like u-boot.
> 
> We have +10K boards deployed so it's not so easy to switch from 18 -> 8 bits.
> I can explicit fix this in U-boot by forcing the legacy mode via a dt flag, but the gut feeling says this will come back to haunt us :)
> 
> /Sean

I honestly don't know about such issue on U-Boot side, maybe you can
try to be more specific on what commit broke the logic for you as there
are not so many of them between the two versions:

$ git l v2018.07..v2020.01 -- drivers/mtd/nand/raw/mxs_nand.c 
1eb69ae4985 common: Move ARM cache operations out of common.h
9ab5f221a5e nand: mxs_nand: add API for switching different BCH layouts
1d43e24b946 i.MX6: nand: add nandbcb command for imx
1001502545f CONFIG_SPL_SYS_[DI]CACHE_OFF: add
04568bd0b6d MTD: nand: mxs_nand: Allow driver to auto setup ECC in SPL
5645df9e00a MTD: NAND: mxs_nand_init_dma: Make mxs_nand_init_dma static
5ae585ba3a8 MTD: mxs_nand: Fix BCH read timeout error on boards requiring ECC
a430fa06a4a mtd: move NAND files into a raw/ subdirectory

Good luck with your debugging,
Miquèl