First steps to OCP device model integration

Matt Porter porter at
Wed Aug 14 01:34:03 EST 2002

On Fri, Aug 09, 2002 at 02:26:05PM +1000, David Gibson wrote:
> THe patch below implements the first steps in transitioning the
> handling of 4xx OCP devices to the unfied device model (in 2.5).  So
> far the code just registers an ocp bus and registers each device
> described in core_ocp on that bus.  The next step is to convert the
> actual device drivers so that that they register with the unified
> driver tree rather than through the old ocp_register() mechanism.

Hi David,

I don't have any concerns about your patch as a starting point,
but I'd like to talk about where we are going with driverfs
integration of proprietary on-chip buses (4xx and other SoCs).
This "first steps" patch shows you registering OCP as a bus
with a name of "Onchip Peripheral Bus".  This seems to trivialize
the bus hierarchy on 4xx and part of the point of driverfs is
to see where devices are located in the physical bus structure
(since management of them may vary based on their location).
I would expect to see "PLB", "OPB", and "ExtBus" registered
for 4xx for correctness.  They may all use the same bus ops
in a reference board implementation (not making use of the EBC
in most cases), but somebody could have some FPGA-based peripherals
hanging from the EBC which require board-specific PM ops and thus
it would be desirable to see and manage at least the External Bus
separately in driverfs.

Matt Porter
porter at
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