Follow up on 4 Gig of DDR on MPC8548E

[Morrison, Tom]

All,

We are running into a very strange problem that I 
am hoping someone here might have some insight upon.

Setup:
   1) 4 Gig of DDR RAM (at physical addresses 0-0xF_FFFF_FFFF)

   2) LTIB/Linux Kernel (2.6.11++) - I know we are behind the
	times, but it was too risky to go with latest/greatest.

   3) U-boot passes a Max MEM of 3 GIG to the kernel at boot...
	But, we are using on the bootcmd ==> mem=2 GIG + a few pages

Symptoms:
  a) 	Kernel boots - but fails / and hangs when it attempts to 
	open the initial console:

>> EXT2-fs warning: mounting unchecked fs, running e2fsck is recommended
>> VFS: Mounted root (ext2 filesystem).
>>  316k init
>> EXT2-fs error (device sda1): ext2_check_page: bad entry in directory
#2: >> unaligned directory entry - offset=0, inode=128,
rec_len=8961,name_len=69
>> Warning: unable to open an initial console.

--- a little debugging indicates that it is trying to open the      ----
--- /dev/console device - and one of first physical pages allocated ----
--- is above the 2 GIG boundary (0x80000000)                        ----

====================further tests==================
   
   b) if we pass a 'mem=2GIG' or less (even though 4 GIG of DDR) - 
	it works correctly, and we boot up normally...

   d) Further, If we do #b, and ioremap a physical address 
	above the 2GIG and read/write those addresses - it works.....
	==> This tells me the memory is working...

My gut tells me this might be something to do with the 2 
Gig boundary and specifically a "signed" versus "unsigned" 
address/offsets mismatch maybe somewhere in the file system??

We are debugging this - but it is painful and slow process 
to narrow the root problem - I am hoping somebody around 
here has some knowledge of this type of failure and can help us!

All the Best~!

Tom Morrison
Principal S/W Engineer
Empirix, Inc (www.empirix.com)
tmorrison at empirix.com
(781) 266 - 3567