PCI bridge aperture too small when devices added

Giuliano Procida (myxie@debian.org)
Thu, 21 Oct 1999 09:40:03 +0100

A colleague, new to Linux, is porting a driver for a device which
consists of (among other things) a PCI bridge and a generic PCI device
(PLX) beyond the bridge. The PLX is only properly configured once some
firmware has been uploaded and started; this sets up various registers
in the PLX including the PCI control registers.

The firmware requires (I think) a 16Mb PCI memory space. However, this
requirement is only apparent once it has been started. The PCI bridge
was configured with a minimal 1Mb aperture at boot and it is not
possible to extend it as other devices occupy the bus address space
immediately beyond the bridge's existing allocation.

What is the most sensible way to proceed? I imagine that the situation
is much the same as when a device is removed/plugged into a bus behind
a bridge. One possibility would be to force Linux to re-scan the
bridge and its children nodes without touching any other PCI devices.

Thanks for any advice,
Giuliano Procida.

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