[PATCH] Workaround for 745x data corruption bug

[Mark A. Greer]

Adrian Cox wrote:

>Recently released errata documents show a new bug in all 745x family
>processors. This can cause data corruption when memory is mapped
>non-coherent and one of these conditions is true:
>1) L2 hardware prefetch is enabled (as it is in Linux)
>2) instructions and data are fetched from the same or adjacent cache
>lines.
>
>The attached patch adds a workaround, by setting CPU_FTR_NEED_COHERENT
>on all 745x processors.
>

Well that sucks (the bug, not the patch :).  Many people like to turn
off coherency when using Marvell host bridges b/c they struggle
performance-wise with coherency on (at least on some versions).

One change to the patch, though.  According to the 7447/7457 errata doc,
rev 1.2 doesn't have the bug.  The attached patch accounts for that.

Mark
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