[gentoo-amd64] Re: disable agpgart support in kernel

[Duncan]

Karol Krizka posted <200603121736.29988.kkrizka@×××××.com>, excerpted
below,  on Sun, 12 Mar 2006 17:36:26 -0800:

> Hello,
> I am trying to disable toe agpgart support in the kernel so I can use the one
> that commes with the binary nvidia drivers. The only problem I have is that I
> can't seem to do it. I located the option under Device Drivers -> Characters
> Devices but there is no checkbx button beside "/dev/agpgart (AGP Support)"
> and it is not disabled because when I grepped though the .config I found:
> CONFIG_AGP=y
> CONFIG_AGP_AMD64=y
> # CONFIG_AGP_INTEL is not set
>
> Is there something I need to do before I am able to disable it? This is
> suspend2-sources-2.6.15-r8 if that matters.

If there's no options beside it, it means you have something else
configured that depends on it, so you have to disable whatever that is in
ordered to have the option to turn what you are looking at off.

The depends (what must be on to have the choice), conflicts (what can't be
on if it's on), and selected-bys (what depends on it so automatically
turns it on) are normally listed in the help text for an item.  This one
is no exception, so check the help text and I'll bet you find one of the
selected-by options on, thereby forcing this one on.

In many cases, simply modularizing the selected-by option will allow the
target option to be modularized as well.  That's all you'd need.

Most likely, your issue is GART_IOMMU, which is the I/O Memory Management
Unit found in the AMD64 chips (Intel's version doesn't have a hardware
IOMMU, but a software emulation of it is enabled by the same option). 
You'll likely want that  enabled if you have >3 gig of memory.  If not, it
doesn't matter and you should be safe turning it off.  Whether NVidia's
GART driver provides the same IOMMU functionality, I don't know.  It
should be documented one way or the other, however, if you look in their
README.  If they don't, and you have >3 gig of memory, you'll likely have
to choose between access to all your memory with the kernel's version, or
running NVidia's version.  I don't know how serious the issue is without
an IOMMU, as I'm just now upgrading to that sort of memory (I have a gig
now but ordered 8 gig coming in next week), but from the help text for the
IOMMU option, it only affects certain 32-bit PCI devices, so it's
/possible/ you could do without an IOMMU.  Note that GART_IOMMU is not
configurable as a  module, so you either have it enabled and built-in or
not.  If you do, then the kernel GART must be built-in and non-modularized
as well, so unless the NVidia version supports the same thing, you don't
have the choice of running the Nvidia GART with IOMMU support, period,
you'll have to choose one or the other.  Of course, if the Nvidia GART
supports it or if you have <=3G memmory, there's no issue, simply disable
the kernel IOMMU and you'll be able to disable the kernel GART as well
(assuming that's the config option that's killing the kernel GART option
presently).

-- 
Duncan - List replies preferred.   No HTML msgs.
"Every nonfree program has a lord, a master --
and if you use the program, he is your master."  Richard Stallman in
http://www.linuxdevcenter.com/pub/a/linux/2004/12/22/rms_interview.html


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