On Sat, Oct 19, 2013 at 2:33 AM, Michael Schmitz
<schmitz@xxxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
With the DISCONTIGMEM memory model, the kernel must be stored in the
first memory block. As ST-RAM is before FastRAM in memory, you cannot
have the kernel in FastRAM without losing ST-RAM (as main memory ---
you can still e.g. ioremap() it for atafb, and use the rest of it as
swap through
a block device like z2ram. This is basically what we do on Amiga with Chip
RAM
and Z2 RAM).
As long as we can ioremap() the ST-RAM frame buffer, we ought to be fine in
the first instance. How useful ST-RAM as swap may be is debatable so I'd
leave that aside for now.
Main benefits would be for users of TTs that have been left out with recent
kernel sizes.
OK - how would I go about ioremaping a chunk of ST-RAM when that has been
left out of the mm setup because it violates the discontigmem layout rules?
Set up a kernel private mapping for all of ST-RAM, and make that available
to the stram allocator?
Just call ioremap(), that takes care of the kernel private mapping.
ioremap() is meant to map anything that is not part of the mm setup.
With the SPARSEMEM memory model, you should be able to store the kernel
in FastRAM and have ST-RAM, too.
I can still remember the headache I got when last playing with the mm code,
I think I'll pass.
But "we" probably have to do that anyway, to please the Amiga BigRAM users.
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
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