lkml.org 
[lkml]   [2007]   [Dec]   [15]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] x86_64: fix problems due to use of "outb" to port 80 on some AMD64x2 laptops, etc.

* H. Peter Anvin <hpa@zytor.com> wrote:

> 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.

i think the native_io_delay() in quirks.c signals the obvious solution:
a DMI (or otherwise) driven quirk that activates a port 0x80 based delay
on such boards. Combined with an iodelay=port80 boot option as well
perhaps, just in case someone hits a system that is not blacklisted yet.
This way such crazy broken hardware can be mapped correctly - like we
map such quirks in every other case. Perhaps even do this workaround on
the PIT driver level. Instead of perpetuating the superstition of port
80 forever.

Ingo


\
 
 \ /
  Last update: 2007-12-15 08:47    [W:1.779 / U:0.292 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site