gpmi-nand ecc

[Sean Nyekjaer]

On 19/04/2021 09.32, Miquel Raynal wrote:
> 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

Hi Miquel,

Thanks for CC'ing the u-boot list :)

commit 616f03dabacb6c500e8a7ceb920cd08554c9fcae
Author: Ye Li <ye.li at nxp.com>
Date:   Mon May 4 22:08:50 2020 +0800

     mtd: gpmi: change the BCH layout setting for large oob NAND

This commit  ^^ introduced the legacy function that was the "primary" 
before.

Guess we can say, that u-boot broke compatibility with the kernel.
I have fixed my setup by enabling the legacy option via dt, in u-boot.

/Sean