Messages in this thread |  | | | Date | Fri, 14 Dec 2007 10:02:57 -0800 | | From | "H. Peter Anvin" <> | | Subject | Re: [PATCH] x86_64: fix problems due to use of "outb" to port 80 on some AMD64x2 laptops, etc. |
Ingo Molnar wrote:
>
> wow, cool fix! (I remember that there were other systems as well that
> are affected by port 0x80 muckery - i thought we had removed port 0x80
> accesses long ago.)
>
> how about the simpler fix below, as a first-level approach? We can then
> remove the _p in/out sequences after this.
>
I believe this will suffer from the issue that was raised: this will use
udelay() long before loop calibration (and no, we can't just "be
conservative" since there is no "conservative" value we can use.)
Worse, I suspect that at least the PIT, which may need to be used for
udelay calibration, is one of the devices that may be affected. I have
seen the Verilog for a contemporary chipset, and it can only access the
PIT once per microsecond -- this actually has to do with the definition
of the PIT; some of the PIT operations are ill-defined if allowed at a
higher frequency than the PIT clock.
-hpa
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