On Fri, Mar 5, 2021 at 7:18 PM Hector Martin [off-list ref] wrote:

On 06/03/2021 02.39, Rob Herring wrote:

quoted

quoted

-       return ioremap(res.start, resource_size(&res));
+       if (res.flags & IORESOURCE_MEM_NONPOSTED)
+               return ioremap_np(res.start, resource_size(&res));
+       else
+               return ioremap(res.start, resource_size(&res));

This and the devm variants all scream for a ioremap_extended()
function. IOW, it would be better if the ioremap flavor was a
parameter. Unless we could implement that just for arm64 first, that's
a lot of refactoring...

I agree, but yeah... that's one big refactor to try to do now...

FWIW, there is ioremap_prot() that Christoph introduced in 2019
for a few architectures.  I suppose it would be nice to lift
that out architecture specific code and completely replace the
unusual variants, leaving only ioremap(), ioremap_prot() and
memremap() but dropping the _nc, _cached, _wc, _wt and _np
versions in favor of an extensible set of flags.

Then again, I would not make that a prerequisite for the merge
of the M1 support.

quoted

What's the code path using these functions on the M1 where we need to
return 'posted'? It's just downstream PCI mappings (PCI memory space),
right? Those would never hit these paths because they don't have a DT
node or if they do the memory space is not part of it. So can't the
check just be:

bool of_mmio_is_nonposted(struct device_node *np)
{
     return np && of_machine_is_compatible("apple,arm-platform");
}

Yes; the implementation was trying to be generic, but AIUI we don't need
this on M1 because the PCI mappings don't go through this codepath, and
nothing else needs posted mode. My first hack was something not too
unlike this, then I was going to get rid of apple,arm-platform and just
have this be a generic mechanism with the properties, but then we added
the optimization to not do the lookups on other platforms, and now we're
coming full circle... :-)

I never liked the idea of having a list of platforms that need a
special hack, please let's not go back to that.

         Arnd