[U-Boot] [PATCH v2] pcm058: fix NAND flash not using badblock table

[Stefano Babic]

Hi Harald,

On 07/12/18 13:18, Marek Vasut wrote:
> On 12/07/2018 01:15 PM, Harald Seiler wrote:
>> Hello Marek,
> 
> Hi,
> 
>> On Fri, 2018-12-07 at 12:48 +0100, Marek Vasut wrote:
>>> On 12/07/2018 10:19 AM, Harald Seiler wrote:
>>>> Currently, U-Boot ignores the BBT stored in the last 4 blocks of NAND
>>>> flash because the NAND_BBT_USE_FLASH flag is not set.  This leads to
>>>> two issues:
>>>>
>>>> * U-Boot silently uses a memory-only BBT which is initialized with all
>>>>   blocks marked as good.  This means, actual bad blocks are marked good
>>>>   and U-Boot might try writing to or reading from them.
>>>> * The BBT in flash, which will be created once Linux boots up, is not
>>>>   off limits for a driver ontop, like UBI.  While it does not seem to
>>>>   consistently produce an error, sometimes UBI will fail to attach
>>>>   because the BBT blocks obviously don't contain valid UBI data.
>>>>
>>>> To fix this, this patch sets the CONFIG_SYS_NAND_USE_FLASH_BBT option,
>>>> which is used in ./drivers/mtd/nand/raw/mxs_nand.c to decide whether
>>>> a BBT in flash is used.
>>>>
>>>> Signed-off-by: Harald Seiler <hws at denx.de>
>>>
>>> V2 Changelog is missing.
>>>
>>>> ---
>>>>  include/configs/pcm058.h | 1 +
>>>>  1 file changed, 1 insertion(+)
>>>>
>>>> diff --git a/include/configs/pcm058.h b/include/configs/pcm058.h
>>>> index 49048c163f..b9bc08b388 100644
>>>> --- a/include/configs/pcm058.h
>>>> +++ b/include/configs/pcm058.h
>>>> @@ -55,6 +55,7 @@
>>>>  #define CONFIG_SYS_NAND_BASE		0x40000000
>>>>  #define CONFIG_SYS_NAND_5_ADDR_CYCLE
>>>>  #define CONFIG_SYS_NAND_ONFI_DETECTION
>>>> +#define CONFIG_SYS_NAND_USE_FLASH_BBT
>>>
>>> Shouldn't this be enabled on all boards with GPMI NAND ?
>>>
>>
>> I looked at other boards and they all defined this config, so I
>> assumed this was the way to go ...

Let me understand. If Isearch for CONFIG_NAND_MXS, I get 27 boards using
this drivers, with different SOC (mx28, mx6[Dual|Quad|Solo], mx6sx,
mx6ull). But none of them is setting  CONFIG_SYS_NAND_USE_FLASH_BBT.

When does it happen the issue ? It should happen if we create a UBI
container and its volumes in U-Boot. If UBI is generated in linux, this
should not happen. Is it the case or does it happen in any condition ?

I think the issue happens because there is a disalignment between kernel
and u-boot. Kernel mainline for this board (file
imx6qdl-phytec-phycore-som.dtsi) sets "nand-on-flash-bbt", while U-Boot
not. That mean that this can always happen if kernel and U-Boot does not
use the same setup for the driver.

Maybe with previous kernel versions there was no problem because Linux
used the same setup as U-Boot.

Anyway, this discourage setting CONFIG_SYS_NAND_USE_FLASH_BBT
unconditionally for all boards with GPMI driver.

> But yes, as far as I understand,
>> it would make sense to have it enabled most of the time.  Although
>> there is some code which makes this configuration from the
>> devicetree, which might be an even better solution.

Device tree has already this option as I see in
drivers/mtd/nand/raw/nand_base.c. The driver enforces this if no DT (as
in this case) is used.

> 
> Cool, if this can be fixed in a more general manner, that'd be awesome
> and would help others too. Better yet, it'd get rid of possibly
> hazardous duplication. Can you research it ?
> 

Best regards,
Stefano

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