[U-Boot] [PATCHv3 3/4] spl: Lightweight UBI and UBI fastmap support

[Tom Rini]

On Mon, Jan 11, 2016 at 12:17:28AM +0100, Ladislav Michl wrote:

> From: Thomas Gleixner <tglx at linutronix.de>
> 
> Booting a payload out of NAND FLASH from the SPL is a crux today, as
> it requires hard partioned FLASH. Not a brilliant idea with the
> reliability of todays NAND FLASH chips.
> 
> The upstream UBI + UBI fastmap implementation which is about to
> brought to u-boot is too heavy weight for SPLs as it provides way more
> functionality than needed for a SPL and does not even fit into the
> restricted SPL areas which are loaded from the SoC boot ROM.
> 
> So this provides a fast and lightweight implementation of UBI scanning
> and UBI fastmap attach. The scan and logical to physical block mapping
> code is developed from scratch, while the fastmap implementation is
> lifted from the linux kernel source and stripped down to fit the SPL
> needs.
> 
> 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
> 
> The code requires quite some storage. The largest and unknown part of
> it is the number of fastmap blocks to read. Therefor the data
> structure is not put into the BSS. The code requires a pointer to free
> memory handed in which is initialized by the UBI attach code itself.
> 
> See doc/README.ubispl for further information on how to use it.
> 
> This shares the ubi-media.h and crc32 implementation of drivers/mtd/ubi
> There is no way to share the fastmap code, as UBISPL only utilizes the
> slightly modified functions ubi_attach_fastmap() and ubi_scan_fastmap()
> from the original kernel ubi fastmap implementation.
> 
> Signed-off-by: Thomas Gleixner <tglx at linutronix.de>
> Signed-off-by: Ladislav Michl <ladis at linux-mips.org>

Reviewed-by: Tom Rini <trini at konsulko.com>

-- 
Tom
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