Re: [RFC/PATCH] x86: Early-boot serial I/O support

[H. Peter Anvin]

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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