[PATCH V2] ARM: mvebu: fix RAM size for Armada XP board DB-MV784MP-GP

On Thu, Mar 14, 2013 at 06:22:16PM +0100, Gregory CLEMENT wrote:

On 03/14/2013 05:56 PM, Jason Cooper wrote:

quoted

On Thu, Mar 14, 2013 at 10:22:36AM -0600, Jason Gunthorpe wrote:

quoted

On Thu, Mar 14, 2013 at 03:57:54PM +0000, Jason Cooper wrote:

quoted

The board is supplied with a 4GB RAM module.  This value can be
overridden by the bootloader based on probed memory size.  We set it to
a reasonable value here.

Signed-off-by: Jason Cooper <redacted>
Changes from v1:
 - grammatical fix suggested by Sergei Shtylyov
 - correct size suggested by several folks (within 32bit, 1 dword)

As promised, catching this fix in the -rc cycle.

For those not familiar, earlier versions of the patch adding this board listed
3GB because that is all that was visible.  I mistaken applied v3 of the patch
instead of v4 which properly listed 4GB.  This patch cleans up my error.

What happens when the kernel tries to treat 0xD0000000 and above as
memory? Lots of internal register blocks overlap 0 -> 4GB - won't this
cause resource conflicts on boot? I'm actually very surprised it boots
at all - what does /proc/iomem say?

We'll have to wait to hear from Gregory or Florian on that.  They are
the only two I know of who have this board.  I can only compile-test.

Indeed there are conflicts with the internals registers. I was too focused
on the size of the RAM itslelf and I forgotten that if we use the 4GB we have
no more address space for the internal registers themselves.
Even with LPAE we will need to leave a "hole" from 0xD0000000 to 0x100000000
for these registers.

So to conclude, currently, if we try to boot the Armada XP GP board with
reg = <0x00000000 0xFFFFFFFF>, the kernel crash, even if there is 4GB of
RAM.

Ok, so for now, we'll go with <0x00000000 0xD0000000>.

thx,

Jason.