Re: IO delay, port 0x80, and BIOS POST codes

[H. Peter Anvin]

Followup to:  <a6qtb8$6fg$[e-mail]>
By author:    [e-mail] (Linus Torvalds)
In newsgroup: linux.dev.kernel
> 
> I suspect the _real_ solution is to stop using "inb_p/outb_p" and make
> the delay explicit, although it may be that some drivers depend on the
> fact that not only is the "outb $0x80" a delay, it also tends to act as
> a posting barrier.
> 

... as well as a push-out to the ISA bus.  I suspect dumping the outb
way of doing it and instead wait in the CPU might cause the delay to
happen in the wrong part of the system (consider split-transaction
queued busses like HyperTransport, where a delay in the CPU doesn't
necessarily mean a delay in the southbridge.)

Port 0x80 has served us well, at least as a default.  If you really
care about the POST display you can recompile using a different port.

	-hpa
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