From mboxrd@z Thu Jan  1 00:00:00 1970
From: Aravind Gopalakrishnan <aravind.gopalakrishnan@amd.com>
Subject: Re: [PATCH] serial: Skip over PCIe device which have no
 quirks (fix AMT regression).
Date: Wed, 5 Mar 2014 16:46:40 -0600
Message-ID: <5317A950.7040103@amd.com>
References: <1394048739-3697-1-git-send-email-konrad.wilk@oracle.com>
	<20140305195657.GA11501@phenom.dumpdata.com>
	<20140305210950.GB11758@phenom.dumpdata.com>
Mime-Version: 1.0
Content-Type: text/plain; charset="us-ascii"; Format="flowed"
Content-Transfer-Encoding: 7bit
Return-path: <xen-devel-bounces@lists.xen.org>
Received: from mail6.bemta5.messagelabs.com ([195.245.231.135])
	by lists.xen.org with esmtp (Exim 4.72)
	(envelope-from <Aravind.Gopalakrishnan@amd.com>) id 1WLKae-0006pl-Rt
	for xen-devel@lists.xenproject.org; Wed, 05 Mar 2014 22:47:05 +0000
In-Reply-To: <20140305210950.GB11758@phenom.dumpdata.com>
List-Unsubscribe: <http://lists.xen.org/cgi-bin/mailman/options/xen-devel>,
	<mailto:xen-devel-request@lists.xen.org?subject=unsubscribe>
List-Post: <mailto:xen-devel@lists.xen.org>
List-Help: <mailto:xen-devel-request@lists.xen.org?subject=help>
List-Subscribe: <http://lists.xen.org/cgi-bin/mailman/listinfo/xen-devel>,
	<mailto:xen-devel-request@lists.xen.org?subject=subscribe>
Sender: xen-devel-bounces@lists.xen.org
Errors-To: xen-devel-bounces@lists.xen.org
To: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>, Konrad Rzeszutek Wilk <konrad@kernel.org>
Cc: "xen-devel@lists.xenproject.org" <xen-devel@lists.xenproject.org>, Keir Fraser <keir@xen.org>, Jan Beulich <jbeulich@suse.com>, "Suthikulpanit, Suravee" <Suravee.Suthikulpanit@amd.com>, "Lendacky, Thomas" <Thomas.Lendacky@amd.com>
List-Id: xen-devel@lists.xenproject.org

On 3/5/2014 3:09 PM, Konrad Rzeszutek Wilk wrote:
> See:
> 00:16.0 Communication controller: Intel Corporation Cougar Point HECI Controller #1 (rev 04)
>          Subsystem: Intel Corporation Device 2008
>          Flags: bus master, fast devsel, latency 0, IRQ 11
>          Memory at fb12a000 (64-bit, non-prefetchable) [size=16]
> 00:16.3 Serial controller: Intel Corporation Cougar Point KT Controller (rev 04) (prog-if 02 [16550])
>          Subsystem: Intel Corporation Device 2008
>          Flags: bus master, 66MHz, fast devsel, latency 0, IRQ 17
>          I/O ports at f0e0 [size=8]
>          Memory at fb129000 (32-bit, non-prefetchable) [size=4K]
>
> pci 0000:00:16.0: [8086:1c3a] type 00 class 0x078000
> pci 0000:00:16.3: [8086:1c3d] type 00 class 0x070002
>
> And Xen picks 00:16.0 as its console when using 'com1=115200,8n1,amt'.
>
> This patch fixes it and allows us to use AMT again by zeroing
> out io_base to zero. If the scan did not work, the io_base is
> set back to a default value.

If you provide 'amt' on command line => 'skip_amt' = 0
Then we'd just return -1 without setting io_base to 0x3f8 due to this 
condition-
if ( !skip_amt )
    return -1;

(or am I missing something?)

>
> diff --git a/xen/drivers/char/ns16550.c b/xen/drivers/char/ns16550.c
> index 487bf7d..9f87018 100644
> --- a/xen/drivers/char/ns16550.c
> +++ b/xen/drivers/char/ns16550.c
> @@ -829,6 +829,7 @@ pci_uart_config (struct ns16550 *uart, int skip_amt, int bar_idx)
>       unsigned int b, d, f, nextf, i;
>       u16 vendor, device;
>   
> +    uart->io_base = 0;

Why not set ns16550.io_base = 0; in arch/x86/setup.c ?
AFAICT, ns16550.c is the only one that uses ns16550_defaults structure, 
so it should be safe..


Thanks,
-Aravind.