[PATCH] omap3_beagle: Change NAND ECC scheme back to OMAP_ECC_HAM1_CODE_HW

[Patrik Dahlstrom]

On 12/22/19 3:48 PM, Adam Ford wrote:
> On Sun, Dec 22, 2019 at 8:28 AM Tom Rini <trini at konsulko.com> wrote:
>>
>> On Sun, Dec 22, 2019 at 08:24:14AM -0600, Derald D. Woods wrote:
>>> On Sun, Dec 22, 2019 at 09:10:50AM -0500, Tom Rini wrote:
>>>> On Sun, Dec 22, 2019 at 09:46:27AM +0100, Patrik Dahlstrom wrote:
>>>>> On 12/22/19 4:24 AM, Derald D. Woods wrote:
>>>>>> On Sat, Dec 21, 2019 at 05:18:22PM +0100, Patrik Dahlström wrote:
>>>>>>> The omap3_beagle NAND ECC scheme was changed in 4b37928d357 for unknown
>>>>>>> reasons, leading to uncorrectible ecc errors. This commit changes it
>>>>>>> back to what it was before.
>>>>>>>
>>>>>>
>>>>>> Hello Patrick,
>>>>>>
>>>>>> Is there a setup/test that you are using for OMAP_ECC_HAM1_CODE_HW? I
>>>>>> just want to give it a try. I have three OMAP3 boards, with NAND, that
>>>>>> I would like to test.
>>>>>
>>>>> I'm using a BeagleBoard rev. C4 (yes, the one that came out in 2009)
>>>>> for testing.
>>>>>
>>>>>>
>>>>>> I also see that the SYS_NAND_ECC_BYTES should have been changed to '14'
>>>>>> per the 'doc/README.nand' for OMAP_ECC_BCH8_CODE_HW_DETECTION_SW. This
>>>>>> may be the issue with this particular ECC scheme.
>>>>>>
>>>>> I based my changes on reverting 4b37928d357, which did this:
>>>>>
>>>>> <snip>
>>>>>  +#define CONFIG_NAND_OMAP_ECCSCHEME      OMAP_ECC_BCH8_CODE_HW_DETECTION_SW
>>>>> <snip>
>>>>>  -#define CONFIG_NAND_OMAP_ECCSCHEME     OMAP_ECC_HAM1_CODE_HW
>>>>> <snip>
>>>>>
>>>>> Based on your comment, I tested this configuration:
>>>>>
>>>>>  #define CONFIG_SYS_NAND_ECCBYTES        14
>>>>>  #define CONFIG_NAND_OMAP_ECCSCHEME      OMAP_ECC_BCH8_CODE_HW_DETECTION_SW
>>>>>
>>>>> It worked to boot from SD card (only had to do saveenv), but only
>>>>> partly from NAND:
>>>>>
>>>>>  U-Boot SPL 2020.01-rc5-00006-gda26dd89c8-dirty (Dec 22 2019 - 09:26:14 +0100)
>>>>>  Trying to boot from NAND
>>>>>
>>>>> Then it just hangs. Here's how I flashed SPL and U-Boot:
>>>>>
>>>>>  mmc rescan
>>>>>  fatload mmc 0 80000000 MLO
>>>>>  nand erase 0 80000
>>>>>  nandecc hw
>>>>>  cp.b 80000000 80020000 20000
>>>>>  cp.b 80000000 80040000 20000
>>>>>  cp.b 80000000 80060000 20000
>>>>>  nand write 80000000 0 80000
>>>>>  fatload mmc 0 80000000 u-boot.img
>>>>>  nand erase 80000 160000
>>>>>  nand write 80000000 80000 160000
>>>>>
>>>>> I then tried adjusting the "nandecc hw" line, but here's how that went:
>>>>>
>>>>>  BeagleBoard # nandecc hw bch8
>>>>>  nand: error: CONFIG_NAND_OMAP_ELM required for ECC
>>>>>
>>>>> Unfortunately CONFIG_NAND_OMAP_ELM is not available for OMAP34XX.
>>>>
>>>> Yeah, ugh, I'm sorry I didn't catch this at the time (my Beagleboard is
>>>> old and I worry about killing the NAND but I guess I need to move it to
>>>> manual testing a few releases a year).  For the beagleboard I believe
>>>> the right answer is to move back to the ECC scheme that it was before as
>>>> that's what's deployed and used by anyone that's using the boards.  If
>>>> memory serves there is a way to switch to doing SW and BCH8 but that's
>>>> not going to be a win for these boards both for speed and for the
>>>> incompatibility.
>>>>
>>>
>>> Tom,
>>>
>>> Are you going to modify the remaining affected OMAP34XX boards? Or will this
>>> patchset be expanded?
>>
>> Lets add in a few more maintainers.  From memory, there are reasons to
>> move to BCH8 on omap3 platforms if for example you're moving to newer
>> NAND chips that in turn require it.  If you want to keep the EVM on
>> BCH8, that's fine, I don't know much about the overall user base there.
>> But I do know the Beagleboard one :)
> 
> I know the Logic PD Torpedo and SOM LV boards use the BCH8 HW
> detection with SW Correction because the omap34/35 had a bit with
> 4-bit and 1-bit wasn't sufficient.  Logic PD has some medical and
> military users so having the 8-bit is preferred.  I haven't checked
> lately, but to my knowledge, the Torpedo and SOM-LV boards have been
> working fine with 8-bit.  I haven't changed them, so unless something
> happened to the driver, I'd prefer to keep the various omap3_logic
> boards as 8-bit.
> 
> I know some of the Micron flash parts have available on-chip ECC, but
> I haven't tried to use them and I don't know of those drivers are
> enabled in U-Boot.  That might be an option for some people who want
> more than 1-bit without the overhead of the software correction on
> devices without ELM.
Since this change only affect omap3_beagle it should be safe to apply, right?
I don't see how it could affect any other board.
> 
> adam
>>
>> --
>> Tom