linux-kernel - Re: [PATCH] i486 CR4 oops, no_console

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Message-ID: <48ACFF0B.6090008@zytor.com>
Date:	Wed, 20 Aug 2008 22:37:15 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	David Fries <david@...es.net>
CC:	Ingo Molnar <mingo@...e.hu>, linux-kernel@...r.kernel.org,
	"Rafael J. Wysocki" <rjw@...k.pl>, Pavel Machek <pavel@....cz>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH] i486 CR4 oops, no_console_suspend

David Fries wrote:
> On Tue, Aug 19, 2008 at 09:07:26AM -0700, H. Peter Anvin wrote:
>> Ingo Molnar wrote:
>>> i've had trouble no end with getting even kernel messages out to the 
>>> serial console during critical phases of suspend/resume. (especially in 
>>> combination with earlyprintk=ttyS0 - not surprisingly)
>>>
>>> Especially during resume the UART is initialized back to something 
>>> really slow - 300 bauds or 9600 bauds. (depends on the chipset i guess) 
>>> So even though it works, it will only worked reliably when i 
>>> standardized all my baud settings to that very low setting.
>>>
>> Probably depends on the BIOS, actually; I suspect you end up with the 
>> standard BIOS setting, which is *usually* 9600 bps.
> 
> I have grub, the kernel, and a getty all set to 115200, for suspend,
> resume, or reboot it's always 115200.  With grub there's no BIOS
> guessing, it sets it to a configured state.
> 

Most likely it never gets reinitialized during resume.  This is a bug, 
obviously.

	-hpa
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