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

[Hans de Goede]

Hi Roy,

On 08-06-15 10:38, Roy Spliet 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 rom (BROM) is no longer active and thus it's inner workings are mostly irrelevant.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
> 2-4MB U-Boot SPL + U-Boot (for recovery)
> 4MB+ Main file system
>
> The mtdparts env variable defines only the main file system because that's the only
> place with relevant files for U-Boot.
> This said: I have replaced the default file system with a "custom" UBI FS containing
> just a boot and a rootfs partition. I am unsure whether these defaults apply for the
> Android image that ships with the Olimex boards. But then again: that image also
> ships with a boot-loader, so do we care?
>> I did not find any document regarding the nand boot partition layout
>> so I would like to see some input from somebody familiar with the
>> driver.
>>
>> While it is fine for testing to hand-edit the environment the final
>> nand support should have
>>
>> 1) way to express the boot partition size in nand pages
>> 2) way to make the main partition start at the end of boot partition
>> and extend to the end of the flash
>>
>> This should probably also go to Linux.
> Linux can define partitions in the device tree. I'd prefer to carry this approach to U-boot,
> but current U-Boot has the partitioning part of the MTD code hacked away and replaced by
> custom mtdparts code without OF support. Doing this proper requires getting rid of the
> latter, which will likely break a lot of legacy. So as far as I agree, I have to warn that is
> a longer-term project, extended further by the ongoing (justified) discussion we are having
> regarding the MTD partitioning code in upstream Linux that may or may not lead to parts
> of the framework being re-architected.

Last time I discussed this with some kernel people, they pointed me to the fact that
the kernel actually parses partition info provided by u-boot through the u-boot mtdparts
command, and that that is the preferred way to pass partition info to the kernel, so rather
then adding dts partition info to u-boot we would need to teach the existing kernel mtdpart
code to deal with separate ecc / random setting and maybe use a list of hardcoded
partitition names for which to use the brom compatible settings. These are all things
which we need to figure out on the kernel side, it would be good to get a discussion
started on this with the kernel mtd people.

Note that we will also need to have a u-boot env partition somewhare either at the
nandpart level, or as a ubi volume, assuming the u-boot env code can deal with
ubi volumes (we are in the full u-boot environment when reading the env.)

Regards,

Hans



>
> Roy
>> Thanks
>>
>> Michal
>
>