[U-Boot] [patch 0/2] SPL: Lightweight UBI and UBI fastmap support

[Heiko Schocher]

Hello Thomas,

Am 05.07.2014 11:48, schrieb Thomas Gleixner:
> Utilizing NAND FLASH requires proper wear leveling and bitflip
> management. Linux choice for this is UBI. The upstream UBI
> implementation is far too big for a SPL, but it is desired to load
> arbitrary payload including u-boot itself from a UBI managed NAND
> FLASH. That restricts the non-UBI managed part of the NAND flash to
> the first few eraseblocks which are reserved for the SoC boot ROM to
> load the SPL.
>
> The following patches provide a lightweight and fast UBI attach and
> load code, which supports fastmap and full scan mode.

Thnaks for your work. I try to look into this patches ASAP...

> The text foot print on the board which I used for development is:
>
>   6854	0	0	6854	1abd	drivers/mtd/ubispl/built-in.o
>
> Attaching a NAND chip with 4096 physical eraseblocks (4 blocks are
> reserved for the SPL) takes:
>
> In full scan mode:	1172ms
> In fastmap mode:	  95ms
>
> With that and a moderate sized kernel image, I'm able to hand off to
> the kernel within less than 500ms.

Great!

> The scan and logical to physical block mapping code is developed from
> scratch, while the fastmap functions are lifted from the linux kernel
> source and adjusted to fit the SPL needs.
>
> The implementation is paranoid and carefully preserves the UBI
> robustness.
>
> For now I keep a private copy of ubi-media.h which should be shared
> with the drivers/mtd/ubi/ one once Heiko has synced it to the 3.14
> source.

Yes, that was also my first thought, as I looked roughly over your
patches.

> There is room for more boot time optimizations:
>
>        - Implement sub page reads for nand_spl_simple
>
>        - Hand the UBI data from SPL to kernel to avoid rescan of the
>          fastmap/flash

bye,
Heiko
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