[PATCH v3 04/32] asm-generic: add ioremap_nopost() remap interface

[Benjamin Herrenschmidt]

On Tue, 2017-04-11 at 15:31 +0100, Lorenzo Pieralisi wrote:
> > This is a semantic that simply *cannot* be generically provided accross
> > architectures as a mapping attribute.
> 
> I agree that a default implementation does not make much sense. The
> only solution to this, if we want the ioremap_nopost to be made available
> to generic code (and drivers - ie DT PCI host bridge drivers on ARM/ARM64
> are not arch code), is to make the ioremap_nopost() call return NULL
> unless overriden by arch code that can provide its semantics.

That would be a better option.

You might be able to implement a fallback, for example by having the
config ops do a read back from the bridge.

Ben.