aperture_64.c: clarify that too small aperture is valid reason for this code

aperture_64.c: clarify that too small aperture is valid reason for this code

[Pavel Machek]

Clarify that too small aperture is valid reason for this code.

Signed-off-by: Pavel Machek <pavel@suse.cz>

diff --git a/arch/x86/kernel/aperture_64.c b/arch/x86/kernel/aperture_64.c
index 9a32b37..026fcfb 100644
--- a/arch/x86/kernel/aperture_64.c
+++ b/arch/x86/kernel/aperture_64.c
@@ -1,8 +1,9 @@
 /*
  * Firmware replacement code.
  *
- * Work around broken BIOSes that don't set an aperture or only set the
- * aperture in the AGP bridge.
+ * Work around broken BIOSes that don't set an aperture, only set the
+ * aperture in the AGP bridge, or set too small aperture.
+ *
  * If all fails map the aperture over some low memory.  This is cheaper than
  * doing bounce buffering. The memory is lost. This is done at early boot
  * because only the bootmem allocator can allocate 32+MB.

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(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

Re: aperture_64.c: clarify that too small aperture is valid reason for this code

[Andi Kleen]

On Wed, Nov 26, 2008 at 05:15:27PM +0100, Pavel Machek wrote:
> 
> Clarify that too small aperture is valid reason for this code.

There are lots more reasons than that, e.g. bad aperture pointing
somewhere invalid.  I'm not sure it makes sense to list them all.

-Andi

Re: aperture_64.c: clarify that too small aperture is valid reason for this code

[Pavel Machek]

> On Wed, Nov 26, 2008 at 05:15:27PM +0100, Pavel Machek wrote:
> > 
> > Clarify that too small aperture is valid reason for this code.
> 
> There are lots more reasons than that, e.g. bad aperture pointing
> somewhere invalid.  I'm not sure it makes sense to list them all.

Small aperture is not "obviously invalid" and it confused me for a
while, but...

									Pavel

-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

Re: aperture_64.c: clarify that too small aperture is valid reason for this code

[Ingo Molnar]

* Pavel Machek <pavel@suse.cz> wrote:

> Clarify that too small aperture is valid reason for this code.
> 
> Signed-off-by: Pavel Machek <pavel@suse.cz>
> 
> diff --git a/arch/x86/kernel/aperture_64.c b/arch/x86/kernel/aperture_64.c
> index 9a32b37..026fcfb 100644
> --- a/arch/x86/kernel/aperture_64.c
> +++ b/arch/x86/kernel/aperture_64.c
> @@ -1,8 +1,9 @@
>  /*
>   * Firmware replacement code.
>   *
> - * Work around broken BIOSes that don't set an aperture or only set the
> - * aperture in the AGP bridge.
> + * Work around broken BIOSes that don't set an aperture, only set the
> + * aperture in the AGP bridge, or set too small aperture.
> + *

applied to tip/x86/iommu, thanks Pavel!

That comment is indeed highly misleading - and sets the wrong mindset for 
people who start reading this file. The list you add it to are indeed the 
most common reasons for us to (re-)allocate the aperture.

Would you be interested in sending a patch for a full list of situations 
where we declare the existing aperture invalid and reallocate it? It will 
certainly help understanding the purpose and role of this file.

	Ingo