Is there a way to ask the Linux Kernel to re-run its PCI initialization code?

13
votes

I'm looking for either a kernel mode call that I can make from a driver, a userland utility, or a system call that will ask the Kernel to look at the PCI bus and either completely re-run its initialization, or initialize a specific device. Specifically, I need the Kernel to recognize a device that was added to the bus after boot and then configure its address space, interrupt, and other configuration parameters, and finally enable the device so that I can load the driver for it (unless this all happens as part of the driver load).

I'm stuck on the 2.4.x series Kernel for this, and am currently working with 2.4.20, but will be moving to 2.4.37 if it matters. The distro is a stripped down Red Hat 7.3 running in a ram disk, but I can add in whatever tools are needed to get this working (as long as they play nice with 2.4 series).

If some background would help clarify what I'm trying to do: From a cold boot, once in Linux I use GPIO to program an FPGA. Part of the FPGA, once programmed, implements a simple PCI device. Currently, after programming the FPGA, I reboot the system and Linux recognizes the device after coming up and loads the driver for it.

Instead of needing that reboot, I'd like to simply ask the Kernel to do whatever it does during boot up to find PCI devices (I have the Kernel configured to find PCI devices on its own, instead of asking the BIOS for that information, so the BIOS won't need to know about this device (I hope)).

I believe that Linux is capable of seeing the device after it is programmed but before a reboot, because scanpci will show the device after I program it, as will lspci -H 1. I just need a way to get it into /proc/pci, configured and enabled.

4
linuxlinux-kernellinux-device-driverpci
You should head over to "sister" site: serverfault.com and ask there. This is for coding-related problems, your exact problem seems to be more of sysadmin related so they might be able to help you faster/better. – Stan

4 Answers

4
votes

This below command will help the user to rescan it complete root hub.

echo "1" > /sys/class/pci_bus/0000\:00/rescan
3
votes

You could speed up the reboot with kexec, if you don't figure out how to get the PCI scan redone. You could ask this on the LKML, if you haven't already.

unloading/reloading the module doesn't help, does it?

2
votes

http://www.linuxjournal.com/article/5633 suggests you should be able to do it with 2.4 kernels using pcihpfs.

If that isn't working, maybe the driver doesn't support hotplug?

1
votes

It would probably crash the system if you reconfigured the addresses of other PCI devices while they are in use.

A better way would be to just configure the new card. If your kernel has support for Cardus devices, it already knows how to configure a newly-inserted PCI device (which is what Cardbus is). You just need to figure out how to get the kernel to do it...

It should be possible for a kernel module to do this. Even if you can't get built-in hotplug code, you should be able to set the pci resources using calls to pci_bus_write_config_dword() and friends. There is probably some IRQ routing setup to do as well.