Re: Linux Post codes during runtime, possibly OT

Pavel Machek
2001-01-27T17:03:43Z

Hi!

> > > > + *
> > > > + * Changed the slow-down I/O port from 0x80 to 0x19. 0x19 is a
> > > > + * DMA controller scratch register. rjohnson@analogic.com
> > > > */
> > > >
> > > What about making that a config option?
> > >
> > > default: delay with 'outb 0x80', other options could be
> > > udelay(n); (n=1,2,3)
> > > outb 0x19
> > >
> > > 0x80 is a safe port, and IMHO changing the port on all i386 systems
> > > because it's needed for some embedded system debuggers is too dangerous.
> > >
> > Dangerous? udelay(1) on a 33 MHz system is like udelay(100). Don't
> > get too used to 800+ MHz CPUs. There are systems, probably most in
> > the world, that need 300 +/- nanosecond delays. This is what the
> > port I/O does.
>
> In most of the cases where this delay is needed, it is a _minimum_
> delay. It is usually time enough for the hardware to react to an index
> register being written to, etc. In most cases, a longer delay on slower
> machines should not hurt.

Except getting your ne2000 slower by factor of 300.
Pavel
--
I'm pavel@ucw.cz. "In my country we have almost anarchy and I don't care."
Panos Katsaloulis describing me w.r.t. patents at discuss@linmodems.org