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

Post by Harald Seiler
Without setting this flag, U-Boot will silently use a memory
only badblock table. This is not only bad because it means badblock
info is ignored, but also leads to other issues if a driver ontop
then tries to read the badblock table as filesystem info (eg. UBI).

Comment is not consistent and does not really explain what happens - can
you formulate it again ? Thanks !

Best regards,
Stefano Babic

Post by Harald Seiler
---
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
#endif
/* DMA stuff, needed for GPMI/MXS NAND support */

--
=====================================================================
DENX Software Engineering GmbH, Managing Director: Wolfgang Denk
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
Phone: +49-8142-66989-53 Fax: +49-8142-66989-80 Email: ***@denx.de
=====================================================================

Harald Seiler

2018-12-07 09:19:36 UTC

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 <***@denx.de>
---
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
#endif

/* DMA stuff, needed for GPMI/MXS NAND support */

--
2.17.2

Marek Vasut

2018-12-07 11:48:09 UTC

Post by Harald Seiler
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
* 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.

V2 Changelog is missing.

Shouldn't this be enabled on all boards with GPMI NAND ?

Post by Harald Seiler
#endif
/* DMA stuff, needed for GPMI/MXS NAND support */

--
Best regards,
Marek Vasut

Harald Seiler

2018-12-07 12:15:16 UTC

Hello Marek,

V2 Changelog is missing.

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 ... 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.

Post by Harald Seiler
#endif
/* DMA stuff, needed for GPMI/MXS NAND support */

--
Harald

DENX Software Engineering GmbH, Managing Director: Wolfgang Denk
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
Phone: +49-8142-66989-62 Fax: +49-8142-66989-80 Email: ***@denx.de

Marek Vasut

2018-12-07 12:18:14 UTC

Post by Harald Seiler
Hello Marek,

Hi,

V2 Changelog is missing.

Shouldn't this be enabled on all boards with GPMI NAND ?

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,
Marek Vasut

Stefano Babic

2018-12-07 18:55:40 UTC

Hi Harald,

Post by Harald Seiler
Hello Marek,

Hi,

V2 Changelog is missing.

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.

Post by Harald Seiler
But yes, as far as I understand,

Post by Harald Seiler
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.

Post by Harald Seiler
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

Harald Seiler

2018-12-07 21:18:02 UTC

Hello Stefano,

Post by Stefano Babic
Hi Harald,

Post by Harald Seiler
Hello Marek,

Hi,

V2 Changelog is missing.

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 ...

Linux will write the badblock table to the last 4 blocks by default which
U-Boot ignores at the moment. So the issue happens if you use the default
kernel config (which you pointed out below).

Post by Stefano Babic
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.

This is exactly what I think is going on ...

Post by Stefano Babic
Anyway, this discourage setting CONFIG_SYS_NAND_USE_FLASH_BBT
unconditionally for all boards with GPMI driver.

I agree, it only makes sense in cases where Linux also does it this way.
Although, not doing it this way means not having any persistent badblock
table at all, which I feel is never a good idea ...

Post by Stefano Babic

Post by Harald Seiler
But yes, as far as I understand,

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.

What do you mean by enforce? If no devicetree is used, the code does not
set any flags as far as I understand it, which also aligns with the results
of my experimentation ... (Currently bbt_options is 0)

Post by Stefano Babic

Best regards,
Stefano

Stefano Babic

2018-12-08 18:44:56 UTC

Hi Harald,

Post by Harald Seiler
Hello Stefano,

Post by Stefano Babic
Hi Harald,

Post by Harald Seiler
Hello Marek,

Hi,

V2 Changelog is missing.

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 ...

Linux will write the badblock table to the last 4 blocks by default which
U-Boot ignores at the moment. So the issue happens if you use the default
kernel config (which you pointed out below).

Right, or in any case where there is a mismatch in the configuration
between U-Boot and Linux.

This is exactly what I think is going on ...

Right.