How can I support memory hole in embedded system?

How can I support memory hole in embedded system?

[dony]

Hello,

        Now I am working on an embedded project based on Linux(X86). The
motherboard has a memory hole at 15M-16M (PCI==>ISA for FlashRom).
        In 2.4.0 arch/i386/boot/setup.S, It introduces an method known as
"E820" which is said to support memory hole .But it uses "int 15" to get
memory regions  from BIOS which cannot be implemented in my case, since my
motherboard has no BIOS, only BSP instead.
        I think we can modify the memory-mapping to support memory hole, but
I don't know how to do it. In mm/bootmem.c it also mentions it can support
memory hole with no more comments.
        Can you give me some information in detail about this? Thank you
very much.

         dony

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Re: How can I support memory hole in embedded system?

[Timur Tabi]

** Reply to message from "dony" <dony.he@huawei.com> on Tue, 26 Sep 2000
09:13:33 +0800


> In 2.4.0 arch/i386/boot/setup.S, It introduces an method known as
> "E820" which is said to support memory hole .But it uses "int 15" to get
> memory regions  from BIOS which cannot be implemented in my case, since my
> motherboard has no BIOS, only BSP instead.

In that case, you can just write an INT 15-like function which pretends to be a
BIOS, and have the Linux kernel call your function instead of a real INT 15.
Your function than just fills out the E820 structure and returns.

You're going to need to do something like this anyway, because if the kernel
tries to call INT 15 on your machine, it will hang.



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Re: How can I support memory hole in embedded system?

[Timur Tabi]

** Reply to message from "dony" <dony.he@huawei.com> on Tue, 26 Sep 2000
09:13:33 +0800


> I think we can modify the memory-mapping to support memory hole, but
> I don't know how to do it. In mm/bootmem.c it also mentions it can support
> memory hole with no more comments.
>         Can you give me some information in detail about this? Thank you
> very much.

Just modify the E820 structure after setup.S calls the BIOS INT 15 routine.


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Timur Tabi - ttabi@interactivesi.com
Interactive Silicon - http://www.interactivesi.com

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