Subject: Re: Can we kill f inb_p, outb_p and other random I/O on port 0x80,
	in 2.6?
From: Alan Cox <alan@lxorguk.ukuu.org.uk>
To: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: arjanv@redhat.com, Jamie Lokier <jamie@shareable.org>,
       Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
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On Llu, 2003-09-22 at 19:58, Eric W. Biederman wrote:
> Alan, can you describe a little more what the original delay is needed
> for?  I don't see it documented in my 8254 data sheet.  The better I
> can understand the problem the better I can write the comments on this
> magic bit of code as I fix it.

If I remember rightly its because it is a 2Mhz part on an 8Mhz bus.

> The oldest machine I have is a 386 MCA system.  Any chance of the bug
> showing up there?  I'd love to have a test case.

No idea

> Another reason for fixing this is we are killing who knows how much
> I/O bandwidth with this stream of failing writes to port 0x80.

Definitely - and if we can boot up with udelay() using some pessimal
value then we don't even need the branch, just the udelay for the 8 ISA
cycles. 

Alan

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