[PATCH] ARM: add support for uncompressed uImage kernel

[Alexander Stein]

Soory for late answer,

On Saturday 13 November 2010, 11:47:41 Albin Tonnerre wrote:
> <linux at arm.linux.org.uk> wrote:
> > Is it really faster to copy an uncompressed image than it is to
> > decompress using LZMA with caches on?
> 
> In my experience, using LZMA is painfully slow on older ARM CPUs.
> 
> If you really need to boot quickly you might want to try LZO, which
> should give you results close to the uncompressed performance. It
> might still be slower though, especially if you're able to load your
> kernel image to memory fairly quickly

We only have experience with GZIP. Our compressed kernel is ~1,8MB and 
uncompressed ~4MB.
On an AT91 ARM9 SoC the decompression takes about 1-2s of time. Caches should 
be disabled, as far as I could see in decompression code.
Copying the uncompressed kernel from NOR to SD-RAM takes about 140ms. So if 
you can afford the additional storage need, simply copying the uncompressed 
kernel is much faster than copying the compressed kernel which decompresses 
itself.

Best regards,
Alexander