[LinuxBIOS] BIOS-provided physical RAM map

How can I adjust the "BIOS-provided physical RAM map" that the linux  
kernel uses? Is this done in northbridge.c with ram_resource()???  
Because mine does not look the same.

ram_resource(dev, idx++, 0, 640);
ram_resource(dev, idx++, 1024, tolmk - 1024);

BIOS-provided physical RAM map:

BIOS-e820: 0000000000001000 - 00000000000a0000 (usable)

BIOS-e820: 0000000000100000 - 0000000008000000 (usable)

128MB LOWMEM available.

Thanks - Joe

[ron minnich]

On 10/13/07, [e-mail]  wrote:
> How can I adjust the "BIOS-provided physical RAM map" that the linux
> kernel uses? Is this done in northbridge.c with ram_resource()???
> Because mine does not look the same.
>
> ram_resource(dev, idx++, 0, 640);
> ram_resource(dev, idx++, 1024, tolmk - 1024);
>
> BIOS-provided physical RAM map:
>
> BIOS-e820: 0000000000001000 - 00000000000a0000 (usable)
>
> BIOS-e820: 0000000000100000 - 0000000008000000 (usable)
>
> 128MB LOWMEM available.

hi joe, I am not sure I understand your question? what is the value of
tolmk in this case?

When booting the kernel, there are a few cmdline parameters you can
use and, if you do, it will IIRC ignore the e820 map. It's been a
while since I looked at that code, though ...

ron

Quoting ron minnich :
> On 10/13/07, [e-mail]  wrote:
> > How can I adjust the "BIOS-provided physical RAM map" that the linux
> > kernel uses? Is this done in northbridge.c with ram_resource()???
> > Because mine does not look the same.
> >
> > ram_resource(dev, idx++, 0, 640);
> > ram_resource(dev, idx++, 1024, tolmk - 1024);
> >
> > BIOS-provided physical RAM map:
> >
> > BIOS-e820: 0000000000001000 - 00000000000a0000 (usable)
> >
> > BIOS-e820: 0000000000100000 - 0000000008000000 (usable)
> >
> > 128MB LOWMEM available.
>
> hi joe, I am not sure I understand your question? what is the value of
> tolmk in this case?
>
> When booting the kernel, there are a few cmdline parameters you can
> use and, if you do, it will IIRC ignore the e820 map. It's been a
> while since I looked at that code, though ...
>
> ron

Well the problem is I don't think the memory regions are allocating  
memory properly still. For example here is the "BIOS-provided physical  
RAM map" from the original bios:

BIOS-provided physical RAM map:

BIOS-e801: 0000000000000000 - 000000000009f000 (usable)

BIOS-e801: 0000000000100000 - 0000000007f00000 (usable)

127MB LOWMEM available.

See how the map ends at 127MB. The last 1MB of memory is pre-allocated  
for the VGA frame buffer (IGD). The original bios excludes this from  
the ram map while LinuxBIOS does not. Linux will think this area is  
useable for system memory and the graphics will think it is useable  
for graphics causing them to write over each other and not good stuff  
will start to happen:-(

Anyways, I am tring to figure out in what code LinuxBIOS configures  
this map so I can make adjustments. Basicly I need to tell LinuxBIOS to:

Total LOWMEM - IGD pre-allocated memory = New LOWMEM

I should be able to do this in northbridge.c right?? But would I  
subtract it from tomk or tolmk??

Thanks - Joe

Quoting [e-mail]:
> Quoting ron minnich :
> > On 10/13/07, [e-mail]  wrote:
> > > How can I adjust the "BIOS-provided physical RAM map" that the linux
> > > kernel uses? Is this done in northbridge.c with ram_resource()???
> > > Because mine does not look the same.
> > >
> > > ram_resource(dev, idx++, 0, 640);
> > > ram_resource(dev, idx++, 1024, tolmk - 1024);
> > >
> > > BIOS-provided physical RAM map:
> > >
> > > BIOS-e820: 0000000000001000 - 00000000000a0000 (usable)
> > >
> > > BIOS-e820: 0000000000100000 - 0000000008000000 (usable)
> > >
> > > 128MB LOWMEM available.
> >
> > hi joe, I am not sure I understand your question? what is the value of
> > tolmk in this case?
> >
> > When booting the kernel, there are a few cmdline parameters you can
> > use and, if you do, it will IIRC ignore the e820 map. It's been a
> > while since I looked at that code, though ...
> >
> > ron
>
> Well the problem is I don't think the memory regions are allocating
> memory properly still. For example here is the "BIOS-provided physical
> RAM map" from the original bios:
>
> BIOS-provided physical RAM map:
>
> BIOS-e801: 0000000000000000 - 000000000009f000 (usable)
>
> BIOS-e801: 0000000000100000 - 0000000007f00000 (usable)
>
> 127MB LOWMEM available.
>
> See how the map ends at 127MB. The last 1MB of memory is pre-allocated
> for the VGA frame buffer (IGD). The original bios excludes this from
> the ram map while LinuxBIOS does not. Linux will think this area is
> useable for system memory and the graphics will think it is useable
> for graphics causing them to write over each other and not good stuff
> will start to happen:-(
>
> Anyways, I am tring to figure out in what code LinuxBIOS configures
> this map so I can make adjustments. Basicly I need to tell LinuxBIOS to:
>
> Total LOWMEM - IGD pre-allocated memory = New LOWMEM
>
> I should be able to do this in northbridge.c right?? But would I
> subtract it from tomk or tolmk??

Yep, I had a feeling. It looks like the AMD gx2 northbridge.c does  
this exact thing.

/* Sort out the framebuffer size */
tomk -= FRAMEBUFFERK;

I will test it and get back.....

Thanks - Joe

Quoting [e-mail]:
> Quoting [e-mail]:
> > Quoting ron minnich :
> > > On 10/13/07, [e-mail]  wrote:
> > > > How can I adjust the "BIOS-provided physical RAM map" that the linux
> > > > kernel uses? Is this done in northbridge.c with ram_resource()???
> > > > Because mine does not look the same.
> > > >
> > > > ram_resource(dev, idx++, 0, 640);
> > > > ram_resource(dev, idx++, 1024, tolmk - 1024);
> > > >
> > > > BIOS-provided physical RAM map:
> > > >
> > > > BIOS-e820: 0000000000001000 - 00000000000a0000 (usable)
> > > >
> > > > BIOS-e820: 0000000000100000 - 0000000008000000 (usable)
> > > >
> > > > 128MB LOWMEM available.
> > >
> > > hi joe, I am not sure I understand your question? what is the value of
> > > tolmk in this case?
> > >
> > > When booting the kernel, there are a few cmdline parameters you can
> > > use and, if you do, it will IIRC ignore the e820 map. It's been a
> > > while since I looked at that code, though ...
> > >
> > > ron
> >
> > Well the problem is I don't think the memory regions are allocating
> > memory properly still. For example here is the "BIOS-provided physical
> > RAM map" from the original bios:
> >
> > BIOS-provided physical RAM map:
> >
> > BIOS-e801: 0000000000000000 - 000000000009f000 (usable)
> >
> > BIOS-e801: 0000000000100000 - 0000000007f00000 (usable)
> >
> > 127MB LOWMEM available.
> >
> > See how the map ends at 127MB. The last 1MB of memory is pre-allocated
> > for the VGA frame buffer (IGD). The original bios excludes this from
> > the ram map while LinuxBIOS does not. Linux will think this area is
> > useable for system memory and the graphics will think it is useable
> > for graphics causing them to write over each other and not good stuff
> > will start to happen:-(
> >
> > Anyways, I am tring to figure out in what code LinuxBIOS configures
> > this map so I can make adjustments. Basicly I need to tell LinuxBIOS to:
> >
> > Total LOWMEM - IGD pre-allocated memory = New LOWMEM
> >
> > I should be able to do this in northbridge.c right?? But would I
> > subtract it from tomk or tolmk??
>
> Yep, I had a feeling. It looks like the AMD gx2 northbridge.c does
> this exact thing.
>
> /* Sort out the framebuffer size */
> tomk -= FRAMEBUFFERK;
>
> I will test it and get back.....
>
> Thanks - Joe

This myth is confirmed. I setup northbridge.c to subtract the IGD  
pre-allocated memory from tomk, and setup the IGD pre-allocated memory  
registers in raminit.c. For this example I used the max 8MB.

BIOS-provided physical RAM map:

BIOS-e820: 0000000000001000 - 00000000000a0000 (usable)

BIOS-e820: 0000000000100000 - 0000000007800000 (usable)

120MB LOWMEM available.

Sweet, that's just one more thing to cross off my list:-)
Thanks - Joe

[Stefan Reinauer]

* [e-mail]  [071014 00:00]:
> How can I adjust the "BIOS-provided physical RAM map" that the linux  
> kernel uses? Is this done in northbridge.c with ram_resource()???  
> Because mine does not look the same.
>
> ram_resource(dev, idx++, 0, 640);
> ram_resource(dev, idx++, 1024, tolmk - 1024);
>
> BIOS-provided physical RAM map:
>   BIOS-e820: 0000000000001000 - 00000000000a0000 (usable)
>   BIOS-e820: 0000000000100000 - 0000000008000000 (usable)
> 128MB LOWMEM available.

If tolmk is 128M this looks fine.

ram_resource takes a base address in kilobytes and a size in kilobytes.

so the second resource above goes from 1024K to tolmk-1024+1024, which
is tolmk.