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List:       openocd-development
Subject:    [Openocd-development] Implementing xscale mrc/mcsr
From:       david-b () pacbell ! net (David Brownell)
Date:       2009-10-30 7:42:16
Message-ID: 200910300042.17351.david-b () pacbell ! net
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On Friday 30 October 2009, ?yvind Harboe wrote:
> Adding support for mrc/mcr interface in XScale in a sensible fashion
> would require updating debug_handler.S.
> 
> Could I define a generic execute mrc/mcr command and rely on
> self modifying code?

No.  Best if you use the approach outlined in one of the XScale
docs referenced in xscale.h ... download the code dynamically
into the minicache, using some reserved cache line.

In this case the code will be simple ... one MRC (or MCR)
instruction and a banch.  (More or less.)  Most of the
work will be invalidating the cacheline then loading it
with those two words; and making sure the existing code
can properly call that code.

(The issue is that you don't want to rely on code that's
not in the cache; not all chips have SRAM.  And minicache
can't be written except via JTAG.  You might be able to
use some of the normal icache, but that gets tricky.)


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