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

[Roy Spliet]

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rom (BROM) is no longer active and thus it's inner workings are mostly 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.

Roy
> Thanks
>
> Michal


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