MOE uses memory originally from IO device

Martin Schröder martin.schroeder at openlimit.com
Thu Jul 3 18:21:43 CEST 2014


My board is equipped with 128MB external DRAM:

> L4 Bootstrapper
>   Build: #1234 Do 3. Jul 17:34:17 CEST 2014, 4.6.2
>   Scanning up to 128 MB RAM
>   Memory size is 128MB (40000000 - 47ffffff)
>   RAM: 0000000040000000 - 0000000047ffffff: 131072kB
>   Total RAM: 128MB

In addition the CPU has 128kb internal RAM (so called On-Chip-RAM) which 
is located at address 0 - 0001ffff.

I want to expose this OCRAM as a virtual device to a (already existing) 
kernel driver within l4linux, so I added these few lines to my config:

> OCRAM => new Device() {
>   .hid= "ocram";
>   new-res Mmio(0x00000000 .. 0x0001FFFF);
> }
>
> client0 => new System_bus() {
>   ...
>   "ocram" = wrap(hw-root.OCRAM);
> }

Unfortunately IO cannot map this device, but maps instead something else 
which is of no use for me:

> io      | <0x1bff0>IOMEM   [00000000000000-0000000001ffff 20000] non-pref (32bit) (align=1ffff flags=4002)
> io      | WARNING: phys mmio resource allocation failed
> io      | <0x1bff0>IOMEM   [00000000000000-0000000001ffff 20000] non-pref (32bit) (align=1ffff flags=4002)
> io      | allocated resource: <0x1bff0>IOMEM   [00000001000000-0000000101ffff 20000] non-pref (align=1ffff flags=4002)

But a few lines up I see:

> MOE: Hello world!
> MOE: found 109032 KByte free memory
> MOE: found RAM from 40000000 to 47000000
> ...

Probably MOE assumes this as normal ram and adds it to its pool.

But how can I inhibit MOE grabbing this piece of RAM and instead assign 
it to the OCRAM device in IO?


Best regards,
    Martin



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