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SubjectRe: [PATCH] x86: provide a DMI based port 0x80 I/O delay override
On 30-12-07 18:06, Ingo Molnar wrote:

> * Rene Herman <rene.herman@keyaccess.nl> wrote:

>> Real ISA systems will also generally respond faster to it than the
>> unused port (this thing actually has an ISA bus but not VGA on it
>> ofcourse) which means that "a perfect delay register" it is not. But
>> yes, I have an actual Am386DX-40 with ISA VGA up and running which
>> also doesn't care either way, about the ones in misc_32.c or anywhere
>> else for that matter.
>
> yeah - and that's typical of most _p() use: most of them are totally
> bogus, but the global existence of the delay was used as a "it _might_
> break system" boogey-man against replacing it.

No delaying at all does break a few systems.

> so _IF_ we do any delay in x86 platform drivers, we at most do a delay
> on the order of the round-trip latency to the same piece of hardware we
> are handling.

Given that part of the problem is 2 MHz devices on a 8 MHz bus, you can't do
this generally.

Rene.


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