[U-Boot] [PATCH 3/3] doc: imx: Add documentation for nandbcb command

[Lukasz Majewski <lukma@denx.de>]

Hi Shyam,

> Signed-off-by: Shyam Saini <shyam.saini@amarulasolutions.com>
> ---
>  doc/imx/common/imx6.txt | 74
> +++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 74
> insertions(+)
> 
> diff --git a/doc/imx/common/imx6.txt b/doc/imx/common/imx6.txt
> index eab88353f6..0b5061128c 100644
> --- a/doc/imx/common/imx6.txt
> +++ b/doc/imx/common/imx6.txt
> @@ -88,3 +88,77 @@ Reading bank 4:
>  
>  Word 0x00000002: 9f027772 00000004
>  
> +NAND Boot on i.MX6 with SPL support
> +--------------------------------------
> +
> +Writing/updating boot image in nand device is not straight forward in
> +i.MX6 platform and it requires boot control block(BCB) to be
> configured. +
> +BCB contains two data structures, Firmware Configuration Block(FCB)
> and +Discovered Bad Block Table(DBBT). FCB has nand timings, DBBT
> search area, +and firmware. See IMX6DQRM Section 8.5.2.2
> +for more information.
> +
> +We can't use 'nand write' command to write SPL/firmware image
> directly +like other platforms does. So we need special setup to
> write BCB block +as per IMX6QDL reference manual 'nandbcb update'
> command do that job. +
> +for nand boot, up on reset bootrom look for FCB structure in
> +first block's if FCB found the nand timings are loaded for
> +further reads. once FCB read done, DTTB will be loaded and
> +finally firmware will be loaded which is boot image.
> +
> +cmd_nandbcb will create FCB these structures
> +by taking mtd partition as an example.

I think that the above sentence has a wrong order. Could you rewrite it?

> +- initial code will erase entire partition
> +- followed by FCB setup, like first 2 blocks for FCB/DBBT write,
> +  and next block for FW1/SPL
> +- write firmware at FW1 block and
> +- finally write fcb/dttb in first 2 block.
> +
> +Typical NAND BCB layout:
> +=======================
> +
> +   no.of blocks = partition size / erasesize
> +   no.of fcb/dbbt blocks = 2
> +   FW1 offset = no.of fcb/dbbt
> +
> +block  0          1          2
> +        -------------------------------
> +       |FCB/DBBT 0|FCB/DBBT 1|  FW 1  |
> +       --------------------------------
> +
> +On summary, nandbcb update will
> +- erase the entire partition
> +- create BCB by creating 2 FCB/BDDT block followed by
> +  1 FW blocks based on partition size and erasesize.
> +- fill FCB/DBBT structures
> +- write FW/SPL in FW1
> +- write FCB/DBBT in first 2 blocks
> +
> +step-1: write SPL
> +
> +icorem6qdl> ext4load mmc 0:1 $loadaddr SPL  
> +39936 bytes read in 10 ms (3.8 MiB/s)
> +
> +icorem6qdl> nandbcb update $loadaddr spl $filesize  
> +device 0 offset 0x0, size 0x9c00
> +Erasing at 0x1c0000 -- 100% complete.
> +NAND fw write: 0x80000 offset, 0xb000 bytes written: OK
> +
> +step-2: write u-boot-dtb.img
> +
> +icorem6qdl> nand erase.part uboot  
> +
> +NAND erase.part: device 0 offset 0x200000, size 0x200000
> +Erasing at 0x3c0000 -- 100% complete.
> +OK
> +
> +icorem6qdl> ext4load mmc 0:1 $loadaddr u-boot-dtb.img  
> +589094 bytes read in 37 ms (15.2 MiB/s)
> +
> +icorem6qdl> nand write ${loadaddr} uboot ${filesize}  
> +
> +NAND write: device 0 offset 0x200000, size 0x8fd26
> + 589094 bytes written: OK
> +icorem6qdl>  

Would it be possible to provide nandbcb show command (I guess that I
can dump it with plain nand read)?

It would present the FCB/DBBT structure. Do you think it is
needed/feasible ?

Best regards,

Lukasz Majewski

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