RFC: Deprecating io_block_mapping
panto at intracom.gr
Wed May 25 16:07:37 EST 2005
Dan Malek wrote:
> On May 24, 2005, at 10:30 PM, Kumar Gala wrote:
>> I know what I've done in the past is either steal a BAT (83xx) or CAM
>> (85xx) entry and then free it up when a proper ioremap can be done later.
> This is even more of a hack than io_block_mapping() because it is often
> obscure and not documented. Several boards have done this in the past
> as well. It's "magic" that occurs, what seems to be minor code changes
> often cause this to break and makes debugging more complex :-)
>> No, as far as a can tell doing a quick glance if we drop
>> io_block_mapping than we can drop setup_io_mappings().
> We've got to have something to address the board unique requirements
> that are currently satisfied by this.
> There is a real problem that we have to solve. Some boards just need
> access to mapped hardware before the VM is set up. You can't just
> remove a feature or tell them their design is wrong. I don't think obscure
> mapping tricks are the solution, either.
> The only solution is to make ioremap() smart enough to properly use
> BATs and CAMs that are available to a processor. I suspect this is going
> to lead to a bunch of also undesirable configuration options to address
> the customizations necessary.
> -- Dan
More information about the Linuxppc-dev