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Date: Thu, 19 Jun 2014 15:14:48 +0800
From: "Chen, Tiejun" <tiejun.chen@intel.com>
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To: jon.baker@viasat.com, linux-pci@vger.kernel.org
CC: "Gogineni, Naveen" <Naveen.Gogineni@viasat.com>
Subject: Re: PCI rescan issue
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On 2014/6/19 9:33, Jon Baker wrote:
> I am trying to find a solution to a Linux PCI rescan problem.
>
> I have CentOS 6.5
>
>     [jbaker@server0 ~]$ uname -a
>     Linux server0 2.6.32-431.5.1.el6.x86_64 #1 SMP Wed Feb 12 00:41:43 
> UTC 2014 x86_64 x86_64 x86_64 GNU/Linux
>
> I have an Altera FPGA PCIe protoboard I am trying to test in a TYAN 
> FT77A-B7059.
>
> We are trying to solve some hotplug/FPGA reload issues; when we reload 
> the FPGA the PCI interface reloads confusing linux pci code.
>
> After bootup the board is seen by the kernel; lscpi shows Altera FPGA 
> PCIe protoboard settings and config space.  We can load our driver and 
> all is well.
>
> When we reload the FPGA lscpi display shows all "ff" for config space.  As

Are you saying all values in the config space are 0xff? If yes, this 
mean the vendor/device ids are invalid, so I'm just curious how OS 
identify this device, and you really can see that with lspci?

Tiejun

> root I tried
>
>     echo 1 > /sys/bus/pci/rescan
>
> But no change to lspci output.
>
> I tried some variants
>
>     echo 1 > /sys/bus/pci/devices/0000:8a:00.0/rescan
>
> no change to lspci output.
>
>     echo 1 > /sys/bus/pci/devices/0000:8a:00.0/remove
>     echo 1 > /sys/bus/pci/rescan
>
> This removed the device and it did not show up again in lscpi.
>
> Kernel has PCI HOTPLUG enabled:
>
>     [jbaker@server0 ~]$ cat /boot/config-2.6.32-431.el6.x86_64 | grep 
> HOTPLUG
>     CONFIG_HOTPLUG=y
>     CONFIG_MEMORY_HOTPLUG=y
>     CONFIG_MEMORY_HOTPLUG_SPARSE=y
>     CONFIG_HOTPLUG_CPU=y
>     CONFIG_ARCH_ENABLE_MEMORY_HOTPLUG=y
>     CONFIG_ACPI_HOTPLUG_CPU=y
>     CONFIG_ACPI_HOTPLUG_MEMORY=y
>     CONFIG_ACPI_HOTPLUG_MEMORY_AUTO_ONLINE=y
>     CONFIG_HOTPLUG_PCI_PCIE=y
>     CONFIG_HOTPLUG_PCI=y
>     CONFIG_HOTPLUG_PCI_FAKE=m
>     CONFIG_HOTPLUG_PCI_ACPI=y
>     CONFIG_HOTPLUG_PCI_ACPI_IBM=m
>     # CONFIG_HOTPLUG_PCI_CPCI is not set
>     CONFIG_HOTPLUG_PCI_SHPC=m
>     [jbaker@server0 ~]$
>
> The kernel has pciehp module loaded, I see pciehp messages in 
> /var/log/messages.
>
> In other distros, on other platforms, echo 1 > /sys/bus/pci/rescan has 
> worked but does not appear to work here for CentOS 6.5 on this hardware.
>
> This problem is much discussed on the web but I have yet to see a 
> solution discussed. I am thinking the 2.6.32-431.5.1.el6.x86_64 kernel 
> may require a patch(es).  The rescan may not be resetting the PCIe card?
>
> Any ideas how to get rescan to work?
>
> Thank you,
>
> Jon Baker
>