linux-kernel - Re: [PATCH] fsldma: use PCI Read Multiple command

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Message-Id: <9B86B565-1A28-46CD-8C30-DECB3EBF0763@kernel.crashing.org>
Date:	Mon, 27 Apr 2009 15:02:03 -0500
From:	Kumar Gala <galak@...nel.crashing.org>
To:	David Hawkins <dwh@...o.caltech.edu>
Cc:	Ira Snyder <iws@...o.caltech.edu>,
	Liu Dave-R63238 <DaveLiu@...escale.com>,
	linux-kernel@...r.kernel.org, linuxppc-dev@...abs.org,
	Dan Williams <dan.j.williams@...el.com>,
	Timur Tabi <timur@...escale.com>
Subject: Re: [PATCH] fsldma: use PCI Read Multiple command


On Apr 27, 2009, at 3:00 PM, David Hawkins wrote:

>
>>> Can you give me an example of non-PCI memory that would be
>>> non-prefetchable that you'd like us to try? We can see if our
>>> host CPUs have an area like that ... we just need to know
>>> what device to look for first :)
>> You can mark the pci inbound window on the 83xx as non-prefetchable  
>> (assuming 83xx is host). On a x86 host I doubt there is any easy  
>> way to get non-prefetchable memory.
>
> Yep, we were going to do that, but chose to use the
> 1MB region already setup for the IMMRs since its already
> marked as non-prefetchable. We were only doing reads, so
> it wasn't going to hurt anything.
>
> I doubt that marking one of the other BAR regions
> as non-prefetchable will give a different result.
> However, we're more than happy to double-check if
> you'd like.

Its possible you'll get a different result since IMMR is a register  
space internal and thats normally a completely different bus than  
memory would be (internal to the 83xx).  I'd suggest double-checking w/ 
a BAR marked non-prefetch pointing to real memory.

- k
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