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

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Date:	Sat, 8 Dec 2007 21:04:27 +0000
From:	Alan Cox <alan@...rguk.ukuu.org.uk>
To:	"David P. Reed" <dpreed@...d.com>
Cc:	Andi Kleen <andi@...stfloor.org>, linux-kernel@...r.kernel.org,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>
Subject: Re: RFC: outb 0x80 in inb_p, outb_p harmful on some modern AMD64
 with MCP51 laptops

> The point here is that Linux is NOT using a defined-to-be "unused" 
> port.  It IS using the "diagnostic" port, and talking to a diagnostic 
> device that *is* used, and may be present.

Just like millions of other pieces of software from the same era. 

> 2) Start a background task with the maintainers of drivers to clean up 
> their code regarding these short delays for slow devices (note that it's 
> never because the *bus* is slow, but because the *device* is slow.)  
> Perhaps this could be helped by "deprecating" the _p calls and 
> suggesting an alternative that requires the coder to be precise about 
> what the delay is for, and how long it is supposed to be, perhaps on a 
> per-machine basis.

Send patches. For a lot of the devices we know what the requirements are
as its locked to ISA cycle times.

Alan
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