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From: "H. Peter Anvin" <hpa@zytor.com>
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
Date: Sat, 10 Jul 2010 11:51:52 -0700	[thread overview]
Message-ID: <4C38C148.2060805@zytor.com> (raw)
In-Reply-To: <1278785277-22629-1-git-send-email-penberg@cs.helsinki.fi>

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

  parent reply	other threads:[~2010-07-10 18:52 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2010-07-10 18:07 [RFC/PATCH] x86: Early-boot serial I/O support Pekka Enberg
2010-07-10 18:38 ` Yinghai Lu
2010-07-10 18:51 ` H. Peter Anvin [this message]
2010-07-10 21:18   ` Pekka Enberg

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