[U-Boot] [linux-sunxi] [RFC 11/11] mtd/nand: Sunxi NAND boot partition definitions

[Michal Suchanek]

On 8 June 2015 at 10:38, Roy Spliet <r.spliet at ultimaker.com> wrote:
> Hello Michal,
>
> Op 07-06-15 om 18:48 schreef Michal Suchanek:
>
> Hello,
>
> On 5 June 2015 at 13:52, Roy Spliet <r.spliet at ultimaker.com> wrote:
>
> Based on the default layout of the android image used at least on Olimex
> Lime
>
> Signed-off-by: Roy Spliet <r.spliet at ultimaker.com>
> ---
>  include/configs/sunxi-common.h | 9 +++++++++
>  1 file changed, 9 insertions(+)
>
> diff --git a/include/configs/sunxi-common.h b/include/configs/sunxi-common.h
> index ec28c40..b38f2f5 100644
> --- a/include/configs/sunxi-common.h
> +++ b/include/configs/sunxi-common.h
> @@ -404,8 +404,15 @@ extern int soft_i2c_gpio_scl;
>  #define BOOT_TARGET_DEVICES_USB(func)
>  #endif
>
> +#ifdef CONFIG_NAND
> +#define BOOT_TARGET_DEVICES_NAND(func) func(NAND, nand , 0)
> +#else
> +#define BOOT_TARGET_DEVICES_NAND(func)
> +#endif
> +
>  #define BOOT_TARGET_DEVICES(func) \
>         BOOT_TARGET_DEVICES_MMC(func) \
> +       BOOT_TARGET_DEVICES_NAND(func) \
>         BOOT_TARGET_DEVICES_SCSI(func) \
>         BOOT_TARGET_DEVICES_USB(func) \
>         func(PXE, pxe, na) \
> @@ -441,6 +448,8 @@ extern int soft_i2c_gpio_scl;
>         MEM_LAYOUT_ENV_SETTINGS \
>         "fdtfile=" CONFIG_DEFAULT_DEVICE_TREE ".dtb\0" \
>         "console=ttyS0,115200\0" \
> +       "mtdids=nand0=mtd2\0" \
> +       "mtdparts=mtdparts=mtd2:0xffc00000 at 0x400000(nand0_main)\0" \
>         BOOTENV
>
> From what I heard the nand boot partition size should be specified in
> nand pages rather than bytes because the boot rom loads a fixed number
> of pages and just uses the start of each page regardless of page size.
>
> Although I believe you have the facts mostly right, they do not apply in
> this situation.
> What you are looking for is the partition definition for U-boot. At this
> point the boot
> rom (BROM) is no longer active and thus it's inner workings are mostly
> irrelevant.
> The NAND partition lay-out for the boards I have seen (various Olimex +
> Cubietruck..)
> are as follows:
> 0-2MB U-Boot-SPL + U-Boot

OK, so 0-2 MB has to be read (at least in part) by brom to load the
SPL so it must be in the format brom understands. The part containing
the SPL which is read by brom has certain number of pages. The u-boot
part can contain whatever we define.

> 2-4MB U-Boot SPL + U-Boot (for recovery)
> 4MB+ Main file system

The main filesystem has to be in format suitable for UBIFS. It has to
follow u-boot part possibly with some space in between.

If support for non-uniform flash format is not available then there
are basically two options:

1) SPL supports brom format and u-boot binary is part of boot
partition. SPL can read/write itself and u-boot and u-boot can
read/write the main partition

2) SPL and u-boot support the main partition format. While u-boot is
written to the boot partition its pages are written in the format
suitable for ubifs. This will get hairy when you want to actually
write u-boot and SPL.

The problem with counting the partition sizes in bytes is obvious -
whatever you do the brom reads predefined number of pages from the
start of the nand to load the SPL and unless you know maximum page
size of every nand ever made that is compatible with Allwinner brom
you cannot tell what is even the maximum size of this part in bytes.

Thanks

Michal