Intel sez: Synchronous Flash and XIP is the future -- thoughts?

[Nicolas Pitre]

On Mon, 16 Dec 2002, David Woodhouse wrote:

> 
> wd at denx.de said:
> > Running the kernel XIP is not so insane. It can help to  reduce  boot
> > time.  We  still  more  than  3  seconds from power-on to application
> > start, which is not so  bad,  but  still  too  much  in  some  cases;
> > avoiding  the  memcpy()  of  some  2 MB of data is kind of attractive
> > then...
> 
> That's true, although even if you have the kernel on a separate flash chip
> to which you don't ever write, it does cost you later because you then run
> from flash which is slower than RAM. I wonder if we could copy the kernel
> from flash to RAM at runtime and fix up the page tables as we go, to get the
> best of both worlds?

On ARM this has no value since the kernel takes up at most 1 or 2 page table 
entries (1MB section descriptors that is).

Fortunately on ARM the kernel seems to be sane with .text and .rodata 
actually being read-only.

/me who incidentally just finished hacking a XIP kernel and filesystem patch
on ARM for a customer named Intel...


Nicolas