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

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To: Rene Herman <rene.herman@...>
Cc: Paul Rolland <rol@...>, H. Peter Anvin <hpa@...>, Krzysztof Halasa <khc@...>, Pavel Machek <pavel@...>, Andi Kleen <andi@...>, Alan Cox <alan@...>, David P. Reed <dpreed@...>, <linux-kernel@...>, Thomas Gleixner <tglx@...>, Ingo Molnar <mingo@...>, <rol@...>
Date: Tuesday, December 11, 2007 - 8:08 am

Rene Herman wrote:

That would be the delay on the i386 (sic) architecture.  In general, 
though, the delay is:

    "Some devices require that accesses to their ports are slowed down. 
    This functionality is provided by appending a _p to the end of the
    function."
    -- Documentation/DocBook/deviceiobook.tmpl


(I've not seen any other formal definition.)

Most architectures (Alpha, Arm, Arm2, Blackfin, FRV, h8300, IA64, 
PA-RISC, PowerPC, Sparc, Sparc64, V850 and Xtensa) do no pause.  M68k 
does no pause except in one configuration, when it's the same as i386.  
On m32r it's a push and a pop.  On SuperH it's similar to i386, only 
using 16-bit input.  X86-64 is the same as i386!

Thinking that _p gives a pause is perhaps too PC-centric.  Why, if a 
delay is needed, wouldn't you use a real delay; one that says how long 
it should be?
--
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Messages in current thread:
Re: RFC: outb 0x80 in inb_p, outb_p harmful on some modern A..., David Newall, (Tue Dec 11, 8:08 am)
Re: RFC: outb 0x80 in inb_p, outb_p harmful on some modern A..., linux-os (Dick Johnson), (Tue Dec 11, 11:41 am)
More info on port 80 symptoms on MCP51 machine., David P. Reed, (Wed Dec 12, 4:07 pm)
Re: More info on port 80 symptoms on MCP51 machine., Rene Herman, (Wed Dec 12, 4:26 pm)
Re: More info on port 80 symptoms on MCP51 machine., Rene Herman, (Wed Dec 12, 4:58 pm)
Re: More info on port 80 symptoms on MCP51 machine., H. Peter Anvin, (Wed Dec 12, 5:05 pm)
Re: More info on port 80 symptoms on MCP51 machine., Chuck Ebbert, (Fri Dec 14, 6:05 pm)
Re: More info on port 80 symptoms on MCP51 machine., Rene Herman, (Sat Dec 15, 3:22 am)
Re: More info on port 80 symptoms on MCP51 machine., H. Peter Anvin, (Wed Dec 12, 5:12 pm)
RE: More info on port 80 symptoms on MCP51 machine., Allen Martin, (Sat Dec 15, 6:34 pm)
Re: More info on port 80 symptoms on MCP51 machine., H. Peter Anvin, (Sat Dec 15, 6:46 pm)
Re: More info on port 80 symptoms on MCP51 machine., David P. Reed, (Wed Dec 12, 4:37 pm)
Re: RFC: outb 0x80 in inb_p, outb_p harmful on some modern A..., linux-os (Dick Johnson), (Tue Dec 11, 4:27 pm)
Re: RFC: outb 0x80 in inb_p, outb_p harmful on some modern A..., linux-os (Dick Johnson), (Wed Dec 12, 9:11 am)
Attitude problems., David P. Reed, (Wed Dec 12, 3:42 pm)
Re: Attitude problems., linux-os (Dick Johnson), (Wed Dec 12, 4:31 pm)
Re: Attitude problems., linux-os (Dick Johnson), (Fri Dec 14, 12:01 pm)
Re: RFC: outb 0x80 in inb_p, outb_p harmful on some modern A..., Dr. David Alan Gilbert, (Sun Dec 9, 9:41 am)
Re: RFC: outb 0x80 in inb_p, outb_p harmful on some modern A..., Lennart Sorensen, (Tue Dec 11, 11:14 am)
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