On 2014/5/31 3:25, Nicolas Pitre Wrote:

On Fri, 30 May 2014, Rob Herring wrote:

quoted

There's work in flight to support early_ioremap, early console, and RO
text patching which all use the fixmap region.

There's a couple of options to solve this:

- Only support up to 16 cpus. It could be anywhere between 17-31, but
that seems somewhat unlikely. Are we really ever going to see 32-bit
32 core systems?

I wouldn't rule that out.  I've seen 16-core ARM chips in 2008 (although 
they didn't go into production).  Silly limitations like that always 
come back to bite you.  And we have better alternatives.New

 Now our team is woring on arma15 with 16 CPUs.

quoted

- Reduce KM_TYPE_NR from 16 to 15. Based on the comment for it, we
probably don't want to do that. Is increasing it to the default of 20
worthwhile? Some of the options here would allow doing that.
- Add 0xffe00000-0xfff00000 to the fixmap region. This would make
fixmap span 2 PMDs with the top PMD having a mixture of uses like we
had before.

That would be my preferred approach.  Note here it could be 
0xffe00000-0xfffe0000 to include the whole of the previous fixmap area 
curently unused.

quoted

- push the PCI i/o space down to 0xfec00000 and make fixmap 4MB. This
is a cleaner solution as the 2 PMDs are only used for fixmap. This may
require some static mapping adjustments on some platforms.

No need.  With the latest changes, the fixmap area is between 0xffc00000 
and 0xffe00000 (there is apparently a mistake in 
Documentation/arm/memory.txt).  So currently 0xff000000-0xffc00000 is 
free, which makes the fixmap area far away from the PCI i/o area with 
plenti of space in between.

quoted

- Same as previous option, but convert the PCI i/o space to fixmap
entries. We don't really need all 2MB for PCI.

See above.

quoted

Also, there is an error in the documentation below:

quoted

Signed-off-by: Liu Hua <redacted>
---
 Documentation/arm/memory.txt   |  2 +-

Yep, good that you spotted it as well.  I failed to catch it during my 
review so I'll send a patch.

Very sorry for the mistake and ignoreing this mail. Maybe I should imporve
my email client!

Thanks again for Nicolas.

Thanks,
Liu Hua

Nicolas

.