On Fri, Apr 27, 2012 at 08:17:48AM -0600, Bjorn Helgaas wrote:
>On Fri, Apr 27, 2012 at 3:27 AM, Richard Yang
><weiyang@xxxxxxxxxxxxxxxxxx> wrote:
>
>I assume your question relates to the Stratus ftServer topology. If
>so, the lspci details might clarify things.
>
Yes, my picture is a little bit related to your previous mail.
While my intention is to find out how the physical world is represented
in the kernel.
Below is a typical topology in PCIe spec r3.0.
+------------------+
| |
| RC |
| Bus#0 |
| ------------- |
| |
+-+-----+--------+-+
00:0.0 | | | 00:02.0
+---------+---------+ | | | +------------+-------------+
| +------+ | +-------| PCIe 2 PCI Bridge |
| PCIe Endpoint | | | |
+-------------------+ | | Bus#2 |
| | -------------- |
| +-------+---------------+--+
| | |
| 00:01.0 |02:00.0 |02:01.0
+------------+-------------+ +-------+------+ +---+-------+
| | |PCI dev | |PCI dev |
| Switch | | | | |
| Bus#1 | | | | |
| --------------- | +--------------+ +-----------+
| |
+------------------------+-+
| |
| |
| 01:00.0 | 01:01.0
+---------+-------+ +--------+----------------+
| | | |
| PCI Endpoint | | PCIe Endpoint |
| | | |
| | | |
+-----------------+ +-------------------------+
Do you think the current assignment of bus number and pci_dev is
correct?
>In that system, my understanding is that 03:01.0 is a downstream port,
>not an upstream port.
>
>I think your picture is slightly misleading because PCIe links are not
>buses; they're point-to-point links between two devices. You've drawn
>#3 and #5 as buses that can have several devices on them, which is not
>really the case. The link from a downstream port should lead to
>exactly one device.
>
>That's one thing that's strange in the ftServer topology: apparently
>there are *two* devices on bus 03: the 03:00.0 upstream port and the
>03:01.0 downstream port. I think 03:00.0 is the upstream port of a
>PCIe switch, which is perfectly normal. My understanding is that
>03:01.0 is another *downstream* port that leads to several more
>devices (USB, NIC, etc).
>
>Bjorn
--
Richard Yang
Help you, Help me
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