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

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Date:	Mon, 17 Dec 2007 15:42:51 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Pavel Machek <pavel@....cz>
Cc:	Alan Cox <alan@...rguk.ukuu.org.uk>, unlisted-recipients:
	no@...is.elte.hu, To-header@...is.elte.hu, on@...is.elte.hu,
	"input <"@elvis.elte.hu, ; Rene Herman <rene.herman@...access.nl>,
	Paul Rolland <rol@...917.net>,
	"H. Peter Anvin" <hpa@...or.com>, Krzysztof Halasa <khc@...waw.pl>,
	Andi Kleen <andi@...stfloor.org>, linux-kernel@...r.kernel.org,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>, rol@...be.net
Subject: Re: RFC: outb 0x80 in inb_p, outb_p harmful on some modern AMD64
	with MCP51 laptops


* Pavel Machek <pavel@....cz> wrote:

> > > > ./char/epca.c 
> > > > ./char/sonypi.c
> > > > ./scsi/megaraid.c
> > > > ./ide/pci/serverworks.c
> > > > ./ide/pci/cmd640.c
> > > > ./input/mouse/pc110pad.c
> > 
> > You are missing some watchdogs at least ?
> 
> I snipped them, I only wanted to comment that pc110pad.c looks like
> legitimate use of outb_p().

since this code seems to run late during bootup (a mouse driver), could 
we replace this with udelay(2), and get rid of that outb_p()? I.e. via 
the patch below?

	Ingo

----------------->
Subject: x86: replace outb_p() with udelay(2) in drivers/input/mouse/pc110pad.c
From: Ingo Molnar <mingo@...e.hu>

replace outb_p() with udelay(2). This is a real ISA device so it likely
needs this particular delay.

Signed-off-by: Ingo Molnar <mingo@...e.hu>
---
 drivers/input/mouse/pc110pad.c |    7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

Index: linux-x86.q/drivers/input/mouse/pc110pad.c
===================================================================
--- linux-x86.q.orig/drivers/input/mouse/pc110pad.c
+++ linux-x86.q/drivers/input/mouse/pc110pad.c
@@ -39,6 +39,7 @@
 #include <linux/init.h>
 #include <linux/interrupt.h>
 #include <linux/pci.h>
+#include <linux/delay.h>
 
 #include <asm/io.h>
 #include <asm/irq.h>
@@ -62,8 +63,10 @@ static irqreturn_t pc110pad_interrupt(in
 	int value     = inb_p(pc110pad_io);
 	int handshake = inb_p(pc110pad_io + 2);
 
-	outb_p(handshake |  1, pc110pad_io + 2);
-	outb_p(handshake & ~1, pc110pad_io + 2);
+	outb(handshake |  1, pc110pad_io + 2);
+	udelay(2);
+	outb(handshake & ~1, pc110pad_io + 2);
+	udelay(2);
 	inb_p(0x64);
 
 	pc110pad_data[pc110pad_count++] = value;
--
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