On Fri, Oct 22, 2010 at 5:57 AM, Leif Sörman leif.sorman@enea.com wrote:
I want to have ram memory above 4G on a freescale p4080 board since I want to test that 36-bits physical addressing is working, my board has two 2G dimm mounted.
We've tested up to 8GB on a P4080DS.
The standard 32-bits u-boot on the board says that it can only handle memory less than 4G.
I have managed to flashed a 36-bits u-boot to the board and now I realized that the 36-bits u-boot
put the two gigs memory below 4G.
The purpose of a 36-bit U-Boot is so that you can have more than 2GB of RAM. I/O devices are placed above 4GB.
Is it possible to change something in u-boot so it put one of the memory device above 4G?
Not really. U-Boot's internal design has quite a few dependencies on having memory starting at address 0. Also, getting the Linux kernel to boot at an address other than 0 is difficult.
Also, even if you have 8GB of memory, it's hard to get Linux to allocate memory above the 4GB range.
I think a better solution for me would be to replace the two memory devices with two 4 gigs devices.
Yes, I agree.
Does u-boot support larger devices?
Yes. The latest upstream U-Boot supports 4GB DDR and maybe even 8GB DDR.
Maybe it's only to put the larger memory in and everything works.
It should.
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