[RFT PATCH v3 12/27] of/address: Add infrastructure to declare MMIO as non-posted

[Rob Herring]

On Mon, Mar 8, 2021 at 2:56 PM Arnd Bergmann <arnd at kernel.org> wrote:
>
> On Mon, Mar 8, 2021 at 10:14 PM Rob Herring <robh at kernel.org> wrote:
> > On Mon, Mar 08, 2021 at 09:29:54PM +0100, Arnd Bergmann wrote:
> > > On Mon, Mar 8, 2021 at 4:56 PM Rob Herring <robh at kernel.org> wrote:
> >
> > Let's just stick with 'nonposted-mmio', but drop 'posted-mmio'. I'd
> > rather know if and when we need 'posted-mmio'. It does need to be added
> > to the DT spec[1] and schema[2] though (GH PRs are fine for both).
>
> I think the reason for having "posted-mmio" is that you cannot properly
> define the PCI host controller nodes on the M1 without that: Since
> nonposted-mmio applies to all child nodes, this would mean the PCI
> memory space gets declared as nonposted by the DT, but the hardware
> requires it to be mapped as posted.

I don't think so. PCI devices wouldn't use any of the code paths in
this patch. They would map their memory space with plain ioremap()
which is posted.

Rob