[RFT PATCH v3 08/27] asm-generic/io.h: Add a non-posted variant of ioremap()

[Arnd Bergmann]

On Wed, Mar 24, 2021 at 7:12 PM Will Deacon <will at kernel.org> wrote:
>
> > +/*
> > + * ioremap_np needs an explicit architecture implementation, as it
> > + * requests stronger semantics than regular ioremap(). Portable drivers
> > + * should instead use one of the higher-level abstractions, like
> > + * devm_ioremap_resource(), to choose the correct variant for any given
> > + * device and bus. Portable drivers with a good reason to want non-posted
> > + * write semantics should always provide an ioremap() fallback in case
> > + * ioremap_np() is not available.
> > + */
> > +#ifndef ioremap_np
> > +#define ioremap_np ioremap_np
> > +static inline void __iomem *ioremap_np(phys_addr_t offset, size_t size)
> > +{
> > +     return NULL;
> > +}
> > +#endif
>
> Can we implement the generic pci_remap_cfgspace() in terms of ioremap_np()
> if it is supported by the architecture? That way, we could avoid defining
> both on arm64.

Good idea. It needs a fallback in case the ioremap_np() fails on most
architectures, but that sounds easy enough.

Since pci_remap_cfgspace() only has custom implementations, it sounds like
we can actually make the generic implementation unconditional in the end,
but that requires adding ioremap_np() on 32-bit as well, and I would keep
that separate from this series.

        Arnd