Message-ID: <4C38C148.2060805@zytor.com>
Date: Sat, 10 Jul 2010 11:51:52 -0700
From: "H. Peter Anvin" <hpa@zytor.com>
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To: Pekka Enberg <penberg@cs.helsinki.fi>
CC: x86@kernel.org, linux-kernel@vger.kernel.org,
       Ingo Molnar <mingo@redhat.com>, Cyrill Gorcunov <gorcunov@gmail.com>
Subject: Re: [RFC/PATCH] x86: Early-boot serial I/O support
References: <1278785277-22629-1-git-send-email-penberg@cs.helsinki.fi>
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On 07/10/2010 11:07 AM, Pekka Enberg wrote:
> This patch adds serial I/O support to very early boot printf(). It's useful for
> debugging boot code when running Linux under KVM, for example. The actual code
> was lifted from early printk.

Yinghai is correct that this really needs to pick apart the command 
line, especially since there is already support for command-line parsing 
in the early boot code.  I suggest we just reuse the earlyprintk= 
option, especially since it's basically the same code and so should have 
the same failure profile.

> +
> +	while ((inb(early_serial_base + LSR)&  XMTRDY) == 0&&  --timeout)
> +		;
> +

cpu_relax(); here, probably.

	-hpa
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