linux-kernel - Re: Re: [PATCH 1/3] x86: fix init_8259A() to not use outb

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Date:	Sun, 17 Feb 2008 23:05:43 -0500
From:	"David P. Reed" <dpreed@...d.com>
To:	Rene Herman <rene.herman@...access.nl>
CC:	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, linux-kernel@...r.kernel.org
Subject: Re: Re: [PATCH 1/3] x86: fix init_8259A() to not use
 outb_pic

Rene Herman wrote:
> On 17-02-08 23:25, Alan Cox wrote:
>
>> On Sun, 17 Feb 2008 16:56:28 -0500 (EST)
>> "David P. Reed" <dpreed@...d.com> wrote:
>>
>>> fix init_8259A() which initializes the 8259 PIC to not use outb_pic,
>>> which is a renamed version of outb_p, and delete outb_pic define.
>>
>> NAK
>>
>> The entire point of inb_pic/outb_pic is to isolate the various methods
>> and keep the logic for delays in one place. Undoing this just creates a
>> nasty mess.
>>
>> Quite probably inb_pic/outb_pic will end up as static inlines that do 
>> inb
>> or outb with a udelay of 1 or 2 but that is where the knowledge belongs.
>
> Additional NAK in sofar that the PIC delays were reported to be 
> necesary with some VIA chipsets earlier in these threads.
>
> Rene.
>
This not being a place where performance matters, I will submit a new 
patch that changes inb_pic and outb_pic to use udelay(2).  However, note 
that init_8259A does not use these consistently in its own accesses to 
the PIC registers.  Should I change it to use the _pic calls whereever 
it touches the PIC registers to be conservative?  Note that there is a 
udelay(100) after the registers are all setup, perhaps this is the real 
VIA requirement...
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