PCI-ISA Bridge not operating

David Brigada
2008-07-11T16:25:53Z

Hi,

I'm working with the MSM800XEV board from Digital-Logic. This board
uses a Geode LX800 for a CPU and has the CS5536 companion board also
installed. The board works with an IT8888G IC that provides a PCI/ISA
bridge to a PC/104 bus that is externally provided.

If I boot with FreeDOS, I can twiddle I/O ports, and the proper ISA
signaling comes over the PC/104 bus. In Linux, the /IOW or /IOR line
goes low as expected, but the address doesn't come over the bus. The
DOS that I'm running doesn't seem to have any specific drivers for the
chip, I'm guessing that the hardware should "just work" --- the IT8888G
is designed to grab I/O requests in the ISA range off the PCI bus after
a short delay if nothing else grabs them first.

I have a feeling that it has something to do with the CS5536 companion
chip, as it seems as though there is a driver for a PCI/ISA bridge on
that chip, though I can't get much detail from AMD's datasheet on that
functionality. I do know that on the MSM800XEV, any such functionality
is wired to the IT8888G, not the CS5536.

There are two kernel config options related to the PCI IDs of the parts
of the device that handle the ISA bus, CONFIG_SCx200_ACB and
CONFIG_CS5535_GPIO. I've tried disabling both, but it doesn't seem to help.

In lspci, the CS5536 PCI/ISA bridge is shown, but not the IT8888G.

Any ideas?

Thanks,
David Brigada