Re: PCI(e) enumeration

[Christian Gmeiner]

Hi Bjorn,

2011/12/15 Bjorn Helgaas <bhelgaas@xxxxxxxxxx>:
> On Thu, Dec 15, 2011 at 2:41 AM, Christian Gmeiner
> <christian.gmeiner@xxxxxxxxx> wrote:
>> Hi all,
>>
>> I maintain a debian based linux RFS in my company and my college does the
>> same for windows. Now we run into a problem that windows and linux use a
>> different network interface as eth0. In our target system there
>> are two identical NICs installed.
>>
>> So I am now looking to find out, how linux does the PCI enumeration
>> and in which order
>> the PCI driver gets called to do the initialization. Can somebody tell
>> me if a depth-first search
>> or a breadth-first search is done on the PCI bus.
>>
>>
>> For instance look at this lspci output:
>>
>> 00:01.0 Host bridge: Advanced Micro Devices [AMD] CS5536 [Geode
>> companion] Host Bridge (rev 33)
>> 00:01.1 VGA compatible controller: Advanced Micro Devices [AMD] Geode LX Video
>> 00:01.2 Entertainment encryption device: Advanced Micro Devices [AMD]
>> Geode LX AES Security Block
>> 00:04.0 Ethernet controller: Intel Corporation 8255xER/82551IT Fast
>> Ethernet Controller (rev 10)
>> 00:0f.0 ISA bridge: Advanced Micro Devices [AMD] CS5536 [Geode
>> companion] ISA (rev 03)
>> 00:0f.2 IDE interface: Advanced Micro Devices [AMD] CS5536 [Geode
>> companion] IDE (rev 01)
>> 00:0f.3 Multimedia audio controller: Advanced Micro Devices [AMD]
>> CS5536 [Geode companion] Audio (rev 01)
>> 00:0f.4 USB Controller: Advanced Micro Devices [AMD] CS5536 [Geode
>> companion] OHC (rev 02)
>> 00:0f.5 USB Controller: Advanced Micro Devices [AMD] CS5536 [Geode
>> companion] EHC (rev 02)
>> 00:0f.7 USB Controller: Advanced Micro Devices [AMD] CS5536 [Geode
>> companion] UOC (rev 02)
>>
>> How will linux does the enumeration?
>
> The kernel enumerates PCI devices with a depth-first traversal, but
> that isn't what determines the ethX device name. ÂThat name is
> determined by the order in which network drivers are loaded and claim
> devices, which gets into distro details like udev.
>
> Here's a nice paper with more details:
> http://www.dell.com/downloads/global/power/ps1q07-20060392-Domsch.pdf

Thanks

>
> If that's not enough to solve your problem, a debian-related forum
> will probably be more useful than LKML.

I don't think that this is a debian related issue, as I use no special
udev rule. Here is the lscpi
output of the target machine, where I have this issue.


root@OT1300:~# lspci
00:00.0 Host bridge: Intel Corporation Atom Processor E6xx PCI Host
Bridge #1 (rev 05)
00:01.0 Host bridge: Intel Corporation Atom Processor E6xx
Configuration Unit (rev 02)
00:02.0 VGA compatible controller: Intel Corporation Atom Processor
E6xx Integrated Graphics Controller (rev 05)
00:03.0 Multimedia video controller: Intel Corporation Atom Processor
E6xx Integrated Graphics Controller (rev 02)
00:17.0 PCI bridge: Intel Corporation Atom Processor E6xx PCI Express
Port 1 (rev 02)
00:18.0 PCI bridge: Intel Corporation Atom Processor E6xx PCI Express
Port 2 (rev 02)
00:19.0 PCI bridge: Intel Corporation Atom Processor E6xx PCI Express
Port 3 (rev 02)
00:1a.0 PCI bridge: Intel Corporation Atom Processor E6xx PCI Express
Port 4 (rev 02)
00:1f.0 ISA bridge: Intel Corporation Atom Processor E6xx LPC Bridge (rev 02)
01:00.0 PCI bridge: Intel Corporation Platform Controller Hub EG20T
PCI Express Port (rev 01)
02:00.0 Unassigned class [ff00]: Intel Corporation Platform Controller
Hub EG20T Packet Hub (rev 01)
02:00.1 Ethernet controller: Intel Corporation Platform Controller Hub
EG20T Gigabit Ethernet Controller (rev 02)
02:00.2 Unassigned class [ff00]: Intel Corporation Platform Controller
Hub EG20T General Purpose IO Controller (rev 01)
02:02.0 USB Controller: Intel Corporation Platform Controller Hub
EG20T USB OHCI Controller #4 (rev 02)
02:02.1 USB Controller: Intel Corporation Platform Controller Hub
EG20T USB OHCI Controller #5 (rev 02)
02:02.2 USB Controller: Intel Corporation Platform Controller Hub
EG20T USB OHCI Controller #6 (rev 02)
02:02.3 USB Controller: Intel Corporation Platform Controller Hub
EG20T USB2 EHCI Controller #2 (rev 02)
02:02.4 USB Controller: Intel Corporation Platform Controller Hub
EG20T USB Client Controller (rev 02)
02:04.0 SD Host controller: Intel Corporation Platform Controller Hub
EG20T SDIO Controller #1 (rev 01)
02:04.1 SD Host controller: Intel Corporation Platform Controller Hub
EG20T SDIO Controller #2 (rev 01)
02:06.0 SATA controller: Intel Corporation Platform Controller Hub
EG20T SATA AHCI Controller (rev 02)
02:08.0 USB Controller: Intel Corporation Platform Controller Hub
EG20T USB OHCI Controller #1 (rev 02)
02:08.1 USB Controller: Intel Corporation Platform Controller Hub
EG20T USB OHCI Controller #2 (rev 02)
02:08.2 USB Controller: Intel Corporation Platform Controller Hub
EG20T USB OHCI Controller #3 (rev 02)
02:08.3 USB Controller: Intel Corporation Platform Controller Hub
EG20T USB2 EHCI Controller #1 (rev 02)
02:0a.0 Unassigned class [ff00]: Intel Corporation Platform Controller
Hub EG20T DMA Controller #1
02:0a.1 Serial controller: Intel Corporation Platform Controller Hub
EG20T UART Controller 0 (rev 01)
02:0a.2 Serial controller: Intel Corporation Platform Controller Hub
EG20T UART Controller 1
02:0a.3 Serial controller: Intel Corporation Platform Controller Hub
EG20T UART Controller 2
02:0a.4 Serial controller: Intel Corporation Platform Controller Hub
EG20T UART Controller 3
02:0c.0 Unassigned class [ff00]: Intel Corporation Platform Controller
Hub EG20T DMA Controller #2
02:0c.1 Serial bus controller [0c80]: Intel Corporation Platform
Controller Hub EG20T Serial Peripheral Interface Bus
02:0c.2 Serial bus controller [0c80]: Intel Corporation Platform
Controller Hub EG20T I2C Controller
02:0c.3 CANBUS: Intel Corporation Platform Controller Hub EG20T
Controller Area Network (CAN) Controller
02:0c.4 Unassigned class [ff00]: Intel Corporation Platform Controller
Hub EG20T IEEE 1588 Hardware Assist (rev 01)
03:00.0 Ethernet controller: Intel Corporation 82574L Gigabit Network Connection
05:00.0 Ethernet controller: Intel Corporation 82574L Gigabit Network Connection


The two important lines are these ones:

03:00.0 Ethernet controller: Intel Corporation 82574L Gigabit Network Connection
05:00.0 Ethernet controller: Intel Corporation 82574L Gigabit Network Connection


As you can see we have two equal network controllers, which both are using the
e1000e driver. In this case I think that the driver gets first control
over 03:00.0
and then over 05:00.0.

So it is the case that
- 03:00.0 is eth0
- 05:00.0 is eth1

To sum it up, if there are two devices handled by the same driver the
device, which is
higher in the pci bus, will become eth0. Or?

I could use udev to change the device numbers, but as its is MAC based
it is no solution
for me. We are selling devices, which run linux on it and we have lots
of MAC addresses :)

In the end I think linux did the assignment correctly, whereas for
windows I did not find
any documentation :(

Greets,
--
Christian Gmeiner, MSc
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