On 18-02-08 22:44, H. Peter Anvin wrote:
Rene Herman wrote:
I mean that before the linux kernel used a port 0x80 write as an I/O
delay it used a short jump (two in a row actually...) as such and this
was at the time that it actually ran on the old legacy stuff that is
of most concern here.
No, if I'm not mistaken, those two jumps are actually what the
udelay() is going to do anyway as part of delay_loop() at that early
stage so that even before loops_per_jiffy calibration, I believe we
should still be okay.
That doesn't make any sense at all. The whole point why the two jumps
were obsoleted with the P5 (or even late P4, if I'm not mistaken) was
because they were utterly insufficient when the CPU ran at something
much higher than the external speed.
Yes, but generally not any P5+ system is going to need the PIT delay in the
first place meaning it just doesn't matter. There were the VIA issues with
the PIC but unless I missed it not with the PIT.
That's the point. It's fairly unclean to say udelay(2) and then not delay
for 2 microseconds but you _have_ done the two short jumps meaning 386 and
486 systems are okay and later systems were okay to start with.
Rene.
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