linux-kernel - Re: Stable kernel 3.8.4/3.9-rc3 breaks PNP serial port

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Date:	Tue, 2 Apr 2013 09:23:36 -0700
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	Josh Boyer <jwboyer@...hat.com>, Sean Young <sean@...s.org>
Cc:	Jiri Slaby <jslaby@...e.cz>, tkil@...ye.com,
	linux-serial@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: Stable kernel 3.8.4/3.9-rc3 breaks PNP serial port

On Tue, Apr 02, 2013 at 11:53:44AM -0400, Josh Boyer wrote:
> Hi All,
> 
> We've had a report [1] that the 3.8.4 stable kernel makes a PNP serial
> port stop working.  After testing 3.8.3, the reporter narrowed it down
> to stable commit eec98f82c637 (tty/8250_pnp: serial port detection
> regression since v3.7) (upstream commit 77e372a3d82).  Reverting that
> single commit from 3.8.5 allows the serial port to continue working.
> 
> The machine in question is using an AMI UEFI implementation as the
> firmware, and on 3.8.3 the serial port has the following in
> /sys/bus/pnp/devices/00:0a/resources
> 
> 	state = active
> 	io disabled
> 	irq 4
> 	dma disabled
> 
> With 3.8.[45], the same file has:
> 
> 	state = disabled
> 	io disabled
> 	irq 4
> 	dma disabled
> 
> In both cases, the io and dma resources are disabled, and an IRQ is
> assigned.  However, the state remains active for the port on 3.8.3.
> 
> The offending commit mentions this is a BIOS bug from InsydeH2O and that
> the port is bogus in that case, but we have something similar here with
> an AMI UEFI implementation (Version: 0406 Release Date: 06/06/2012)
> where the port isn't bogus.
> 
> I'm not sure exactly what the solution should be here.  Any thoughts?

Sean, should I just revert this patch now, and wait for a better fix
later?

thanks,

greg k-h
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