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Date: Wed, 23 Jul 2008 13:12:18 -0700
From: Andrew Morton <akpm@linux-foundation.org>
To: Yinghai Lu <yhlu.kernel@gmail.com>
Cc: mingo@elte.hu, tglx@linutronix.de, hpa@zytor.com, andi@firstfloor.org,
       arjan@infradead.org, ebiederm@xmission.com, greg@kroah.com,
       linux-kernel@vger.kernel.org
Subject: Re: [PATCH] x86: usb debug port early console
Message-Id: <20080723131218.f03ed672.akpm@linux-foundation.org>
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On Wed, 23 Jul 2008 12:52:20 -0700
Yinghai Lu <yhlu.kernel@gmail.com> wrote:

> 
> 
> based on work from Eric, and add some timeout so don't dead loop when debug device
> is not installed
> 
>
> ...
>
> +static void dbgp_mdelay(int ms)
> +{
> +	int i;
> +	while (ms--) {
> +		for (i = 0; i < 1000; i++)
> +			outb(0x1, 0x80);
> +	}
> +}

hm.  port 80 has a guaranteed one microsecond?  Why not
udelay()/mdelay()/etc?

> +static void dbgp_breath(void)
> +{
> +	/* Sleep to give the debug port a chance to breathe */
> +}

I expect the compiler will optimise away any calls to this.

>
> ...
>
> --- linux-2.6.orig/arch/x86/kernel/head64.c
> +++ linux-2.6/arch/x86/kernel/head64.c
> @@ -72,6 +72,8 @@ static void __init copy_bootdata(char *r
>  	}
>  }
>  
> +extern void __init enable_debug_console(char *buf);

Please always pass all patches through scripts/checkpatch.pl.