linux-kernel - Re: PCI express switch handling ..

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Message-ID: <20100315053209.GC28926@lackof.org>
Date:	Sun, 14 Mar 2010 23:32:09 -0600
From:	Grant Grundler <grundler@...isc-linux.org>
To:	Manu Abraham <abraham.manu@...il.com>
Cc:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	linux-pci@...r.kernel.org,
	Grant Grundler <grundler@...isc-linux.org>
Subject: Re: PCI express switch handling ..

On Sun, Mar 14, 2010 at 11:18:05PM +0400, Manu Abraham wrote:
> Hi All,
> 
> I have one of these PCIe switches on one of the PCIe cards that I have:
> 
> http://www.plxtech.com/products/expresslane/pex8604
> 
> I was wondering how to handle this thing, ie;
> 
> I have to PCIe devices behind this switch, which looks thus:
> 
> 06:00.0 PCI bridge: PLX Technology, Inc. Device 8604 (rev ba)
> 07:01.0 PCI bridge: PLX Technology, Inc. Device 8604 (rev ba)
> 07:04.0 PCI bridge: PLX Technology, Inc. Device 8604 (rev ba)
> 07:05.0 PCI bridge: PLX Technology, Inc. Device 8604 (rev ba)
> 09:00.0 Multimedia controller: Philips Semiconductors Device 7231 (rev aa)
> 0a:00.0 Multimedia controller: Philips Semiconductors Device 7231 (rev aa)

Can you post "lspci -vt" and "lspci -v" output?
It will tell us alot more about the heirarchy and address space routing.

> I am wondering if i need to access or address the switch specifically
> to forward data specifically to one of the bridges behind the switch.

No. MMIO routing is handling by MMIO "window" register in the bridge.

While it's called a "switch" because it can route MMIO transactions
from one downstream PCI-e link to any other.

> At present I can access one of the Multimedia controllers (09:00.0) ,
> but it seems I can't access the other one and hence my question as to
> determine whether it is something else.

"lspci -vt" will show what is visible in PCI Config space.

"lspci -v" will tell us how the bridge is configured.

hth,
grant
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