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Re: [Qemu-discuss] Coldfire 5282 Support

From: Peter Maydell
Subject: Re: [Qemu-discuss] Coldfire 5282 Support
Date: Wed, 25 Oct 2017 07:37:26 +0100

On 24 October 2017 at 21:34, William Mahoney <address@hidden> wrote:
> Quick question. On the MCF5282 there is a huge memory mapped IO starting at 
> 0x40000000 and going for 1A0000. All of the IO is relative to this starting 
> point, so when my call back for an I/O write happens, for example, I get the 
> offset into the area. Fine.

What's actually in this region that wants the offset from the
base of it? Often "all the IO is in this window" designs are
really just "there are lots of different IO devices which
are at different places within this range". That is, is
there actually any behaviour needed for "in the IO range
but not actually a device" ?

> 1) If I define the large region and THEN define the small one (since FEC 
> support is already done), will the “more recent” region get the I/O requests 
> and I’m good to go? And if so, will my “below the FEC” part and the “above 
> the FEC” part still have the correct offsets?

You can do this sort of thing, but you need to define
the region priorities (using memory_region_add_subregion_overlap()
for at least one of them. See docs/devel/memory.txt and
in particular the section on overlapping regions.

-- PMM

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