Re: [PATCH] x86: provide a DMI based port 0x80 I/O delay override
From: Rene Herman
Date: Sun Dec 30 2007 - 12:57:47 EST
On 30-12-07 18:06, Ingo Molnar wrote:
* Rene Herman <rene.herman@xxxxxxxxxxxx> 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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