how to use memory before kernel load address?

how to use memory before kernel load address?

[zhuzhenhua]

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hello,all
          i want to place my kernel loadaddr=0x81008000 and set
EBASE=0x81000000, it workes.
         but there is still some memory usable before 0x81000000, for
example from 0x80100000 ~ 0x80200000
         i have try to pass param as mem=1M@1M mem=16M@16M  to the kernel,
it seems only take the 0x8000000 ~ kernel_end as reserved.
         is there any other options to set the memory useable? ( my kernel
version is 2.6.14)
         thanks for any hints


zzh

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Re: [SPAM] how to use memory before kernel load address?

[Markus Gothe]

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Are you using a MTD, if so just create a partition there.

//Markus

On 20 Nov 2007, at 02:06, zhuzhenhua wrote:

> hello,all
>           i want to place my kernel loadaddr=0x81008000 and set  
> EBASE=0x81000000, it workes.
>          but there is still some memory usable before 0x81000000,  
> for example from 0x80100000 ~ 0x80200000
>          i have try to pass param as mem=1M@1M mem=16M@16M  to the  
> kernel,  it seems only take the 0x8000000 ~ kernel_end as reserved.
>          is there any other options to set the memory useable? ( my  
> kernel version is 2.6.14)
>          thanks for any hints
>
>
> zzh


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Re: how to use memory before kernel load address?

[Thiemo Seufer]

zhuzhenhua wrote:
> hello,all
>           i want to place my kernel loadaddr=0x81008000 and set
> EBASE=0x81000000, it workes.
>          but there is still some memory usable before 0x81000000, for
> example from 0x80100000 ~ 0x80200000

The obvious thing to do seems to set LOARADDR to 0x80208000.

>          i have try to pass param as mem=1M@1M mem=16M@16M  to the kernel,
> it seems only take the 0x8000000 ~ kernel_end as reserved.
>          is there any other options to set the memory useable? ( my kernel
> version is 2.6.14)
>          thanks for any hints

AFAIR the kernel assumes to occupy the lowest addresses of the usable RAM.


Thiemo

Re: how to use memory before kernel load address?

[Atsushi Nemoto]

On Tue, 20 Nov 2007 13:04:51 +0000, Thiemo Seufer <ths@networkno.de> wrote:
> >          i have try to pass param as mem=1M@1M mem=16M@16M  to the kernel,
> > it seems only take the 0x8000000 ~ kernel_end as reserved.
> >          is there any other options to set the memory useable? ( my kernel
> > version is 2.6.14)
> >          thanks for any hints
> 
> AFAIR the kernel assumes to occupy the lowest addresses of the usable RAM.

You can use prom_free_prom_memory() to give some low pages back to kernel.

---
Atsushi Nemoto

Re: how to use memory before kernel load address?

[zhuzhenhua]

On 11/20/07, Thiemo Seufer <ths@networkno.de> wrote:
> zhuzhenhua wrote:
> > hello,all
> >           i want to place my kernel loadaddr=0x81008000 and set
> > EBASE=0x81000000, it workes.
> >          but there is still some memory usable before 0x81000000, for
> > example from 0x80100000 ~ 0x80200000
>
> The obvious thing to do seems to set LOARADDR to 0x80208000.
>
> >          i have try to pass param as mem=1M@1M mem=16M@16M  to the kernel,
> > it seems only take the 0x8000000 ~ kernel_end as reserved.
> >          is there any other options to set the memory useable? ( my kernel
> > version is 2.6.14)
> >          thanks for any hints
>
> AFAIR the kernel assumes to occupy the lowest addresses of the usable RAM.
>
>
> Thiemo
>

i have resolve it, by modify as follow:

in arch/mips/kernel/setup.c

static inline void bootmem_init(void)
.....
	if (curr_pfn < start_pfn)                    // just change the judgement
			curr_pfn = start_pfn;
                 ....
		/* Register lowmem ranges */
		free_bootmem(PFN_PHYS(curr_pfn), PFN_PHYS(size));

thanks all.

zzh