Re: [PATCH -v3 3/3] PCI,pciehp: use PCIe DSN to identify devicechange during suspend

[Bjorn Helgaas]

On Mon, Jul 29, 2013 at 9:46 PM, Yijing Wang <wangyijing@xxxxxxxxxx> wrote:
>> I'm not sure this is implemented at the correct place.  The idea of
>> using the serial number to detect card swaps is not really specific to
>> pciehp.  I know the Device Serial Number capability is defined in the
>> PCIe spec, but it doesn't *require* any PCIe functionality, and
>> there's no reason a similar capability couldn't be defined for
>> conventional PCI.
>>
>> I don't know much about it, but conventional PCI *does* in fact
>> support the VPD capability, which can contain a serial number.  I
>> wonder if we should enhance pci_device_serial_number() to look for a
>> VPD serial number if there's no PCIe DSN.  Then we would want this
>> check for card swap in a more generic place, e.g., somewhere in
>> pci_scan_slot(), so all forms of hotplug would benefit from it.
>
> Hi Bjorn,
>    I'm reworking this patch, but found some strange info about vpd serial number.
> I have two x86 machines, they almost have the same hardware topology. But by lspci,
> I found two different Broadcom BCM5709 NIC in different machine have the same vpd serial
> number. If this is normal, vpd serial number seems to be useless for identify device change.

I wouldn't say it's completely useless.  If the VPD serial number
changes, we can be pretty confident that the card has changed.  It's
just that if the VPD serial number is unchanged, we might incorrectly
assume it's the same device.

But we currently *always* assume it's the same device, since we don't
look at serial numbers at all.  If we can detect some changes, that
should be an improvement over what we have today even though it's not
perfect.

> The first machine:
> linux:/home/yijing # lspci -vvv -s 0000:01:00.0
> 01:00.0 Ethernet controller: Broadcom Corporation NetXtreme II BCM5709 Gigabit Ethernet (rev 20)
>         Subsystem: Broadcom Corporation NetXtreme II BCM5709 Gigabit Ethernet
>         Control: I/O- Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR- FastB2B- DisINTx-
>         Status: Cap+ 66MHz- UDF- FastB2B- ParErr- DEVSEL=fast >TAbort- <TAbort- <MAbort- >SERR- <PERR- INTx-
>         Latency: 0, Cache Line Size: 256 bytes
>         Interrupt: pin A routed to IRQ 28
>         Region 0: Memory at c0000000 (64-bit, non-prefetchable) [size=32M]
>         Capabilities: [48] Power Management version 3
>                 Flags: PMEClk- DSI- D1- D2- AuxCurrent=0mA PME(D0+,D1-,D2-,D3hot+,D3cold+)
>                 Status: D0 NoSoftRst+ PME-Enable- DSel=0 DScale=1 PME-
>         Capabilities: [50] Vital Product Data
>                 Product Name: Broadcom NetXtreme II Ethernet Controller
>                 Read-only fields:
>                         [PN] Part number: BCM95706A0
>                         [EC] Engineering changes: 220197-2
>                         [SN] Serial number: 0123456789
>                         [MN] Manufacture ID: 31 34 65 34
>                         [RV] Reserved: checksum good, 31 byte(s) reserved
>                 End
>         Capabilities: [58] MSI: Enable- Count=1/16 Maskable- 64bit+
>                 Address: 0000000000000000  Data: 0000
>         ..............[snip]...................
>
> The second machine:
> linux-suse-vmdq:~/pciutils-3.2.0 # ./lspci -vvv -s 01:00.0
> 01:00.0 Ethernet controller: Broadcom Corporation NetXtreme II BCM5709 Gigabit Ethernet (rev 20)
>         Subsystem: Broadcom Corporation NetXtreme II BCM5709 Gigabit Ethernet
>         Control: I/O- Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR- FastB2B- DisINTx-
>         Status: Cap+ 66MHz- UDF- FastB2B- ParErr- DEVSEL=fast >TAbort- <TAbort- <MAbort- >SERR- <PERR- INTx-
>         Latency: 0, Cache Line Size: 256 bytes
>         Interrupt: pin A routed to IRQ 28
>         Region 0: Memory at f6000000 (64-bit, non-prefetchable) [size=32M]
>         Capabilities: [48] Power Management version 3
>                 Flags: PMEClk- DSI- D1- D2- AuxCurrent=0mA PME(D0+,D1-,D2-,D3hot+,D3cold+)
>                 Status: D0 NoSoftRst+ PME-Enable- DSel=0 DScale=1 PME-
>         Capabilities: [50] Vital Product Data
>                 Product Name: Broadcom NetXtreme II Ethernet Controller
>                 Read-only fields:
>                         [PN] Part number: BCM95706A0
>                         [EC] Engineering changes: 220197-2
>                         [SN] Serial number: 0123456789
>                         [MN] Manufacture ID: 31 34 65 34
>                         [RV] Reserved: checksum good, 31 byte(s) reserved
>                 End
>         .......[snip]........
>
>
>>
>> Also, I think it's possible to use acpiphp for ExpressCard slots, and
>> this patch doesn't help acpiphp detect card swaps.  I don't see any
>> mention of suspend/resume in acpiphp, so I don't know if it does
>> anything at all to detect card changes while suspended.  Maybe Rafael
>> can shed some light?
>>
>> I put the first two patches on a pci/yijing-dsn-v3 branch while we
>> work out the details of this one.
>>
>> Bjorn
>>
>>>         } else if (!list_empty(&pbus->devices)) {
>>>                 pciehp_disable_slot(slot);
>>>         }
>>> --
>>> 1.7.1
>>>
>>>
>>
>> .
>>
>
>
> --
> Thanks!
> Yijing
>
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