[PATCH] at91sam9x5: for ROM base address (bugfix for nand ECC)

[PATCH] at91sam9x5: for ROM base address (bugfix for nand ECC)

[Alessandro Rubini]

From: Edoardo Scaglia <scaglia@amelchem.com>

The ROM base address in the 9x5 processors lives at 1M, not 4M,
where SMD is, as defined later in the same file.

The ROM includes some tables that are used to build error-correction data
for NAND memory.  By using the wrong address, we get wrong data and
the result is undetected bit flips (data at 0x408000 is all zeroes).

Thus, even though our kernel was fixing bit errors in NAND, barebox
was not fixing them. With UBI (our situation) we got I/O errors because
the checksum verification for data nodes failed.

Using the proper address corrects the problem: barebox reports a
"bitflip" message, consistent with the kernel message for the same
file, and the files are properly loaded and booted.

Note: the kernel has the same wrong define, but then the magic number
0x00108000 as spelled in arch/arm/boot/dts/at91sam9x5.dtsi is used
instead of the symbolic name.

Signed-off-by: Edoardo Scaglia <scaglia@amelchem.com>
Signed-off-by: Federico Braghiroli <braghiroli@amelchem.com>
Signed-off-by: Alessndro Rubini <rubini@gnudd.com>
---
 arch/arm/mach-at91/include/mach/at91sam9x5.h |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/arch/arm/mach-at91/include/mach/at91sam9x5.h b/arch/arm/mach-at91/include/mach/at91sam9x5.h
index 7ba2e3b..e230577 100644
--- a/arch/arm/mach-at91/include/mach/at91sam9x5.h
+++ b/arch/arm/mach-at91/include/mach/at91sam9x5.h
@@ -144,7 +144,7 @@
 #define AT91SAM9X5_SRAM_BASE	0x00300000	/* Internal SRAM base address */
 #define AT91SAM9X5_SRAM_SIZE	SZ_32K		/* Internal SRAM size (32Kb) */
 
-#define AT91SAM9X5_ROM_BASE	0x00400000	/* Internal ROM base address */
+#define AT91SAM9X5_ROM_BASE	0x00100000	/* Internal ROM base address */
 #define AT91SAM9X5_ROM_SIZE	SZ_64K		/* Internal ROM size (64Kb) */
 
 #define AT91SAM9X5_SMD_BASE	0x00400000	/* SMD Controller */
-- 
1.7.7.2

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Re: [PATCH] at91sam9x5: for ROM base address (bugfix for nand ECC)

[Alessandro Rubini]

> Subject: [PATCH] at91sam9x5: for ROM base address (bugfix for nand ECC)

Argh! After a lot of editing, the subject line is wrong.

   fix ROM base address (bugfix for nand ECC)

Anyways, let me add this detail.  The current code considers the
case where dev_request_mem_region() fails.

        host->pmecc_rom_base = dev_request_mem_region(dev, 3);
        if (!host->pmecc_rom_base) {
                   [...]

What it does in "[...]" is creating the tables with proper math..  I
tried to skip the request_mem_region() above and ECC works perfectly,
with the software-generated table.

So I wonder whether it makes sense to just remove the declaration of
the ROM are memory-region-3 for NAND, and just use the software-built
tables.

This wouldn't void the previous patch: the ROM address is wrong
as defined, for all CPU types that fall under "at91sam9x5" (I checked
the 5 data sheets: G15, G35, X25, G25, X35).

thanks
/alessandro

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Re: [PATCH] at91sam9x5: for ROM base address (bugfix for nand ECC)

[Alexandre Belloni]

On 01/10/2015 at 23:48:01 +0200, Alessandro Rubini wrote :
> From: Edoardo Scaglia <scaglia@amelchem.com>
> 
> The ROM base address in the 9x5 processors lives at 1M, not 4M,
> where SMD is, as defined later in the same file.
> 
> The ROM includes some tables that are used to build error-correction data
> for NAND memory.  By using the wrong address, we get wrong data and
> the result is undetected bit flips (data at 0x408000 is all zeroes).
> 
> Thus, even though our kernel was fixing bit errors in NAND, barebox
> was not fixing them. With UBI (our situation) we got I/O errors because
> the checksum verification for data nodes failed.
> 
> Using the proper address corrects the problem: barebox reports a
> "bitflip" message, consistent with the kernel message for the same
> file, and the files are properly loaded and booted.
> 
> Note: the kernel has the same wrong define, but then the magic number
> 0x00108000 as spelled in arch/arm/boot/dts/at91sam9x5.dtsi is used
> instead of the symbolic name.
> 
> Signed-off-by: Edoardo Scaglia <scaglia@amelchem.com>
> Signed-off-by: Federico Braghiroli <braghiroli@amelchem.com>
> Signed-off-by: Alessndro Rubini <rubini@gnudd.com>
                     ^
Typo in your name here


-- 
Alexandre Belloni, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com

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Re: [PATCH] at91sam9x5: for ROM base address (bugfix for nand ECC)

[Sascha Hauer]

On Thu, Oct 01, 2015 at 11:59:36PM +0200, Alessandro Rubini wrote:
> > Subject: [PATCH] at91sam9x5: for ROM base address (bugfix for nand ECC)
> 
> Argh! After a lot of editing, the subject line is wrong.
> 
>    fix ROM base address (bugfix for nand ECC)

I applied the patch with this spelling fix and your name written
correctly.

> 
> Anyways, let me add this detail.  The current code considers the
> case where dev_request_mem_region() fails.
> 
>         host->pmecc_rom_base = dev_request_mem_region(dev, 3);
>         if (!host->pmecc_rom_base) {
>                    [...]
> 
> What it does in "[...]" is creating the tables with proper math..  I
> tried to skip the request_mem_region() above and ECC works perfectly,
> with the software-generated table.
> 
> So I wonder whether it makes sense to just remove the declaration of
> the ROM are memory-region-3 for NAND, and just use the software-built
> tables.

Are the software defined tables on all SoCs identical to the ROM tables?
If not that may be a reason to use the software tables only as a
fallback.

Sascha

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