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Re: Modpost warning on Alchemy

To: Sergei Shtylyov <>
Subject: Re: Modpost warning on Alchemy
From: "Maciej W. Rozycki" <>
Date: Thu, 2 Aug 2007 10:14:49 +0100 (BST)
Cc: Ralf Baechle <>,
In-reply-to: <>
Original-recipient: rfc822;
References: <> <> <> <> <> <> <> <> <> <> <>
On Wed, 1 Aug 2007, Sergei Shtylyov wrote:

> > So what is the issue with the size then?  How big is the area?
>    I've already said: 4 gigs! At least in theory, actually it's 2 gigs due to

 Oh, I mistook it for the base physical address, sorry.

> a device # being limited to 0 thru 19 (address bits 11 thru 30 are used as
> IDSELx).

 It does not help too much with a 32-bit virtual address space indeed.  
Though I gather it has to be very sparsely populated as 16MiB is enough to 
cover the whole configuration space of a single PCI bus tree.  Thus it has 
to be another example where the chip designer "forgot" to talk to software 
people.  Or a shifter was traded for software performance and complexity. 

>    I meant that the implementation "caches" the 8 KiB mapping used for the
> last config. access.

 Ah, that can certainly be done with ioremap().

>    There was no need to tell me about how KSEG0/1/2 work -- that's why I
> cosidered it wasting time. :-)

 As I say -- the key is how you look at it.  There are other readers on 
the list who may benefit; it is archived too.  In this sense I can hardly 
consider it a waste of time.  And it was fun to explain and no fun shall 
be ever considered of no use. :-)


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