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

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Message-ID: <20071227103941.GA5353@ucw.cz>
Date:	Thu, 27 Dec 2007 10:39:42 +0000
From:	Pavel Machek <pavel@....cz>
To:	Ingo Molnar <mingo@...e.hu>
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

On Mon 2007-12-17 15:42:51, Ingo Molnar wrote:
> 
> * 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?

Yes, that should work. But I do not have pc110 to verify it.
> 
> 	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>

ACK.


>  	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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