Setting I&D cache enable in the same mtspr instruction
Becky Bruce
Becky.Bruce at freescale.com
Thu Jun 1 09:06:43 EST 2006
I think we need to hold off on this particular patch for a few days.
I took a look at the manual section you're referencing here, and sure
enough, it says that you shouldn't set both bits in the same mtspr
instruction. The manual says this in more than one place, in fact.
However, that seemed a little bit odd to me, so I talked with a few
of the hardware designers for the 745x family. They assure me that
the manual statement is false. The normal code that sets ICE/ICFI/
DCE/DCFI all on one mtspr should be fully functional on this
processor family. I'm still working on confirming this and getting
some history on *why* the manual says that, but for now I'd say it's
a pretty good bet that the manual is in error. I will let you know
if I find out this is not the case.
You are correct, though, in that an isync is needed prior to the
write of HID0[ICE]. It's probably missing because it's not listed in
the synchronization table in chapter 2 of the manual.
For what it's worth, as soon as I can confirm this, I will make sure
the publications team here at Freescale is made aware of the error so
it can be corrected in the next printing of the manual. I will also
have the synchronization table updated as it also has incorrect
information.
Thanks,
B
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