ECC configuration and NAND problems

[gudjon]

Hi list

I to have problem with unreliable NAND-flash. I noticed that my board producer had changed the NAND-flash from
Toshiba TC58NVG1S3ETA00 to
Micron mt29F2G08abaeawp
but I am not sure this has led to increased number of defect boards.

There is a lot of literature on how to make NAND-flash more reliable, increasing number of ECC bits and even adding a redundant boot system.https://www.ronetix.at/an014_SAMA5D3x_8bit_ECC.html

My board only has 2 ECC bits per 512 bytes. The NAND data sheet says 4 ECC bits is minimum. I would like to change the ECC bits to 8 but I don't know how. At what point is the number of ECC bits set?
I have a sama5d3 xplained board. Is there somewhere instructions on how to increase the number of ECC bytes from 4 to 8 for that board?

The nand flash is defined in the following way in the dts file, sama5d3.dtsi.

Code: Select all

nand0: nand@60000000 {
compatible = "atmel,at91rm9200-nand";
#address-cells = <1>;
#size-cells = <1>;
ranges;
reg = <	0x60000000 0x01000000	/* EBI CS3 */
0xffffc070 0x00000490	/* SMC PMECC regs */
0xffffc500 0x00000100	/* SMC PMECC Error Location regs */
0x00110000 0x00018000	/* ROM code */
>;
interrupts = <5 IRQ_TYPE_LEVEL_HIGH 6>;
atmel,nand-addr-offset = <21>;
atmel,nand-cmd-offset = <22>;
atmel,nand-has-dma;
pinctrl-names = "default";
pinctrl-0 = <&pinctrl_nand0_ale_cle>;
atmel,pmecc-lookup-table-offset = <0x0 0x8000>;
status = "disabled";

nfc@70000000 {
compatible = "atmel,sama5d3-nfc";
#address-cells = <1>;
#size-cells = <1>;
reg = <
0x70000000 0x08000000	/* NFC Command Registers */
0xffffc000 0x00000070	/* NFC HSMC regs */
0x00200000 0x00100000	/* NFC SRAM banks */
>;
clocks = <&hsmc_clk>;
};
};

Can anyone point me to any documentation about these parameters?
Or please explain the following parameters:
/* ROM code */ in reg <>
atmel,pmecc-lookup-table-offset
/* NFC Command Registers */
I am not sure my parameters are correct.

Regards
Gudjon

[gudjon]

Hi again list

Replying to my own post. Should have found out earlier but it is in fact pretty easy to change number of ECC bits from 2 to 4 but I don't know how to change the number to 8.
At https://www.at91.com/linux4sam/bin/view ... 1Bootstrap I read that for 8 bit ECC the OOB should be set to 224 bytes and the offset to 120 but Sam-ba gives me an error of
"-E- Script error: -E- Pmecc header configuration failed!".
Is it possible to change the number of ECC bits to 8?

Regards
Gudjon

[blue_z]

There is a lot of literature on how to make NAND-flash more reliable, increasing number of ECC bits and even adding a redundant boot system.https://www.ronetix.at/an014_SAMA5D3x_8bit_ECC.html

You seem to be exaggerating when you claim there is "a lot", but that article probably has the answer(s) you're looking for.

BTW that scheme by Ronetix does not include DTB images (although the DTB can be appended to the kernel with a penalty to flexibility). That omission plus the limitation/hassle of multiple kernel partitions can be solved by storing the kernel and DTB images within the root filesystem (i.e. the /boot/ directory), since U-Boot has the capability of reading files from UBIFS or JFFS2.
Ideally you want as much of the NAND to be part of the filesystem (or UBI volume) as possible (rather than as raw partitions) so that wear-leveling (and bad-block management) can be more effective.
Buildroot has the capability of installing the kernel and dtb in the rootfs image for you.

At what point is the number of ECC bits set?

AFAIK each program that uses the NFC (NAND Flash Controller) can/will configure the NFC for the PMECC parameters.
By "each program", I mean RomBOOT, AT91Bootstrap, U-Boot, the Linux kernel, and SAM-BA.

I have a sama5d3 xplained board.

This could be part of your problem.
You claim to be using an Atmel board, yet also state that you have NAND chips that are not used by the Atmel reference board.
Both claims cannot be true!
Nor will a specific solution work for all cases.

If you have a custom board or a board that is not 100% compatible with an Atmel reference board design, then stop calling it an Atmel board. Do not use an Atmel .dts file as your Device Tree. Instead write a new .dts file for your board.

Is there somewhere instructions on how to increase the number of ECC bytes from 4 to 8 for that board?

Did you study the Ronetix instructions?

The nand flash is defined in the following way in the dts file, sama5d3.dtsi.

Code: Select all

nand0: nand@60000000 {
compatible = "atmel,at91rm9200-nand";
  ...  

(You're conflating the .dts file type with the .dtsi file type, which is sloppy thinking. A .dts is like a .c that contains main(), whereas .dtsi are included files like .h.)
That particular .dtsi file is the description for the generic SAMA5D3x SoC, and usable by any board that has that SoC installed.
The lines you show are for the NAND interface and the NAND Controller of the SoC, not a specific NAND storage chip installed on a board.
PMECC parameters would be properties associated with a specific NAND storage chip, which would be declared in a board-level DT file.

Can anyone point me to any documentation about these parameters?

Look in the kernel source: Documentation/devicetree/bindings/mtd/atmel-nand.txt
Beware that this documentation does not bother to distinguish between SoC-level properties and board-level properties.

Is it possible to change the number of ECC bits to 8?

Since I have not actually done it, I don't have a definitive answer.
But if you claim you have an Atmel reference board, but you actually do not, then SAM-BA is probably not going to do the right thing for you.
I don't know for sure, but to me, it looks like SAM-BA has hardcoded the NAND Header Value for each (Atmel) board.
You probably need to study section 11.4.4.1 NAND Flash Boot: NAND Flash Detection / NAND Flash Specific Header Detection in the SAMA5D3 Series datasheet, this section of the link you mentioned, and this thread.

Regards

[gudjon]

Hi blue_z

Thanks for the answer. I'm sorry for exaggerating the problem. TI has another secure boot solution http://processors.wiki.ti.com/index.php ... ide#NAND_2. They use several bootstraps but only a single u-boot,kernel, dts.

In my production system I use Shiratech AT-501 board but I also have a Sama5d3_xplained to play with. Shiratech changed the NAND flash from Toshiba to Micron. As far as I can see the Micron NAND flash is exactly the same as in sama5d3_xplained but the pullup resistors in the Shiratech card are 470kOhms instead of 100kOhms which I think is irrelevant.
I mentioned the Xplained board because there is a larger probability that somebody has made 8 bit PMECC on that board.

The NAND definitions from sama5d3.dtsi seem to be the ones that are used. These have changed since kernel 3.10, I am using version 4.4.

The definition from 3.10 is:

Code: Select all

nand0: nand@60000000 {
    compatible = "atmel,at91rm9200-nand";
    #address-cells = <1>;
    #size-cells = <1>;
    ranges;
    reg = <	0x60000000 0x01000000	/* EBI CS3 */
        0xffffc070 0x00000490	/* SMC PMECC regs */
        0xffffc500 0x00000100	/* SMC PMECC Error Location regs */
        0x00100000 0x00100000	/* ROM code */
        >;
    interrupts = <5 IRQ_TYPE_LEVEL_HIGH 6>;
    atmel,nand-addr-offset = <21>;
    atmel,nand-cmd-offset = <22>;
    atmel,nand-has-dma;
    pinctrl-names = "default";
    pinctrl-0 = <&pinctrl_nand0_ale_cle>;
    atmel,pmecc-lookup-table-offset = <0x10000 0x18000>;
    status = "disabled";

    nfc@70000000 {
        compatible = "atmel,sama5d3-nfc";
        #address-cells = <1>;
        #size-cells = <1>;
        reg = <
            0x70000000 0x08000000	/* NFC Command Registers */
            0x78000000 0x4		/* NFC busy Registers */
            0xffffc000 0x00000070	/* NFC HSMC regs */
            0x00200000 0x00100000	/* NFC SRAM banks */
            >;
        atmel,write-by-sram;
    };
};

Do both definitions apply to the Micron mt29F2G08abaeawp chip?

Regarding moving the kernel to the UBI filesystem, thanks for the hint. I will start looking for that solution.

Now I will do my homework.

Regards
Gudjon

[gudjon]

Hi again

Two questions related to the discussion:

1. Is there any documentation on how to boot from a kernel within the ubifs? I have tried and failed.

2. Has anyone managed to use 8 ECC bits on sama5d3_xplained? Changing between 2 and 4 is no problem but using 8 doesn't work. I guess the OOB area must be resized but I don't know how to do that.

Regards
Gudjon

[gudjon]

Hi again list

Hope I'm not irritating you with obvious questions

I found some relevant info on question 1.

Code: Select all

u-boot> setenv mtdids nand0=atmel_nand
u-boot> setenv mtdparts 'mtdparts=atmel_nand:256k(bootstrap)ro,512k(uboot)ro,256K(env),256k(evn_redundent),256k(spare),512k(dtb),6M(kernel)ro'
u-boot> mtdparts
device nand0 <atmel_nand>, # parts = 7
 #: name		size		offset		mask_flags
 0: bootstrap           0x00040000	0x00000000	1
 1: uboot               0x00080000	0x00040000	1
 2: env                 0x00040000	0x000c0000	0
 3: evn_redundent       0x00040000	0x00100000	0
 4: spare               0x00040000	0x00140000	0
 5: dtb                 0x00080000	0x00180000	0
 6: kernel              0x00600000	0x00200000	1

active partition: nand0,0 - (bootstrap) 0x00040000 @ 0x00000000

Which is the correct partition table up to the UBIFS but if I add the UBIFS I get an error:

Code: Select all

setenv mtdparts 'mtdparts=atmel_nand:256k(bootstrap)ro,512k(uboot)ro,256K(env),256k(evn_redundent),256k(spare),512k(dtb),6M(kernel)ro,-(rootfs) rootfstype=ubifs ubi.mtd=7 root=ubi0:ro                                                                                                                                                                                          mtdparts
unexpected character ' ' at the end of partition

Thanks for any help.

Regards
Gudjon

[blue_z]

The definition from 3.10 is:
...
Do both definitions apply to the Micron mt29F2G08abaeawp chip?

That looks to be the same DT nodes as your previous post, therefore I would have the same response as before.

1. Is there any documentation on how to boot from a kernel within the ubifs? I have tried and failed.

Don't go off-topic; start a new thread for a new topic.

Has anyone managed to use 8 ECC bits on sama5d3_xplained? Changing between 2 and 4 is no problem but using 8 doesn't work. I guess the OOB area must be resized but I don't know how to do that.

U-Boot can dump the OOB bytes.
That's what I used the last time I had to figure out the proper offset.

Regards

[gudjon]

Hi list and blue_z

The only progress I have made with this problem is to change from 2 ECC bits to 4.
But that seems to have made a huge difference in reliability.

I may not have mentioned that the system is not battery powered and hard power
offs are the usual way of shutting the system down.

I will continue working on 8-Bit ECC, moving the kernel and dt to the ubifs and figuring
out the difference in the device tree between kernel 3.10 and 4.4 for the nand flash.

Thanks for all hints and help and I promise to be on topic

[blue_z]

While looking at AT91Bootstrap for another question, I noticed that you probably have to do some custom configuration, i.e. use `make menuconfig`. Since you want to use more than the minimum number of ECC bits, then you probably have to disable "Auto-detect ONFI minimum error requirement", which then allows specification of "PMECC Error Correction Bits".

If I was doing this, I would divide and conquer the problems. First build a custom version of AT91Bootstrap (with 8 bits of ECC) to load U-Boot from NAND, but install the boot.bin binary on SDcard instead of NAND. Use SAM-BA with modified PMECC configuration to write the U-Boot image to NAND. Then focus on getting AT91Bootstrap (from SDcard) to load U-Boot (from NAND). Once you have a working AT91Bootstrap, then work on booting it from NAND.

BTW the NAND on the SAMA5D4 XULT uses 8 bits of ECC, but that's the chip's minimum requirement.

Also study Enable and Configure PMECC

Beware that each boot program will have to be customized for the PMECC changes.
For U-Boot study the doc/README.atmel_pmecc file in the U-Boot source tree.

Regards

[gudjon]

Thanks for the answer blue_z

Now I have tested the 4 bit PMECC configuration for a few months and more or less all my problems are gone.

I would like to change to 8 bit PMECC but I get the following error when I try to configure the NAND-flash in Sam-ba

According to:
https://www.at91.com/linux4sam/bin/view ... 1Bootstrap
I should set:

8 bit pmecc in 512 byte sector, one page has 8 sectors, spare size: 224, ecc offset: 120
setenv pmecc_header 0xc1e04e07

But I get the following error message in Sam-Ba (version 2.18).

Ecc type is 2 Ecc Status is 2
-I- Configure trimffs 0
-I- PMECC c1e04e07 to be Configured
-E- Script error: -E- Pmecc header configration failed!

I will have to lower the priority of 8-bit PMECC but I will post the solution as soon as I find it.

Now I have the problem of updating from 2 to 4 bit PMECC from within the embedded Linux system but this will be a new topic.

Regards
Gudjon

[blue_z]

But I get the following error message in Sam-Ba (version 2.18).

You could look at the source code for SAM-BA to determine why you're getting that message.

If I was doing this, I would divide and conquer the problems (and abandon SAM-BA).
First build custom versions of AT91Bootstrap (to load a U-Boot from SDcard) and U-Boot (with 8-bit ECC capability and CONFIG_CMD_NAND_TRIMFFS enabled), and install the boot.bin and u-boot.bin binaries on SDcard.
Boot from SDcard and get this U-Boot with modified PMECC configuration to erase, write, read and verify NAND flash.
Then use this custom U-Boot to install another new AT91Bootstrap (with 8-bit ECC capability and to load U-Boot from NAND) and U-Boot to NAND.
First focus on booting AT91Bootstrap (from NAND) to load U-Boot (from NAND).
Once you have that working, then use U-Boot to install the rest of the images to NAND flash.

For installing the AT91Bootstrap image to NAND flash using U-Boot, see these instructions.

Regards

[gselabs]

The following table from the FAQ post http://microchip.force.com/microchipkno ... -in-SAM-BA is very useful in case of NAND header configuration in SAM-BA:

Code: Select all

The following table shows the PMECC encoding data size for different configurations:
CORRECTION CAPABILITY / 512-BYTE SECTOR / 1024-BYTE SECTOR
2 bits / 4 Bytes / 4 Bytes
4 bits / 7 Bytes / 7 Bytes
8 bits / 13 Bytes / 14 Bytes
12 bits / 20 Bytes / 21 Bytes
24 bits / 39 Bytes / 42 Bytes

AFAIK, there is absent of the first column in Atmel datasheets. But without this information it's difficult to calculate the eccOffset field of the NAND header. The Microchip support has provided me the following "cheat-sheet" named "SAMA5D2 and Boot with Nandflash.pdf" which I found very useful, so I don't understand why it is not a part of the official documentation. But I can't attach the PDF file to this forum....