Re: RFC: outb 0x80 in inb_p, outb_p harmful on some modern AMD64 with MCP51 laptops

Alan Cox
2007-12-09T22:36:08Z

On Sun, 9 Dec 2007 22:25:13 +0100
Pavel Machek <pavel@ucw.cz> wrote:

> On Sun 2007-12-09 17:59:08, Andi Kleen wrote:
> > > I mean, we expect 8usec delay -- historical ISA timing -- but when
> > > _PCI_ card with leds is inserted, it is likely to be faster than old
> > > ISA, right?
> >
> > Yes, i guess switching to udelay at least on newer systems would
> > be a good idea. I'm not quite sure about systems without TSC though.
>
> Something like this? (Warning, will not probably even compile on
> x86-64, I do not have 64-bit compiler near me).

You need to stick in a bug trap to verify that the udelay is not called
before the cpu timer has been set up.