On Tue, 29 Jul 2014 17:06:42 +0300, Stanimir Varbanov [off-list ref] wrote:

Arnd, thanks for the comments.

On 07/29/2014 03:00 PM, Arnd Bergmann wrote:

quoted

On Tuesday 29 July 2014 14:42:31 Stanimir Varbanov wrote:

quoted

        taddr = of_translate_address(dev, addrp);
-       if (taddr == OF_BAD_ADDR)
-               return -EINVAL;
+       /*
+        * if the address is non-translatable to cpu physical address
+        * fallback to a IORESOURCE_REG resource.
+        */
+       if (taddr == OF_BAD_ADDR) {
+               memset(r, 0, sizeof(*r));
+               taddr = of_read_number(addrp, 1);
+               if (taddr == OF_BAD_ADDR)
+                       return -EINVAL;
+               r->start = taddr;
+               r->end = taddr + size - 1;
+               r->flags = IORESOURCE_REG;
+               r->name = name ? name : dev->full_name;
+               return 0;
+       }
+

I don't think that everything returning OF_BAD_ADDR makes sense
to turn into IORESOURCE_REG. It could be an e.g. invalid DT
representation, a node with #size-cells=<0>, or it could be
something that gets translated one or more nodes up in the
tree before it reaches a bus without a ranges property.

Also, you should not rely on #address-cells being hardcoded
to <1> above.

This was just an example. Of course it has many issues and probaly it is
wrong:) The main goal was to understand does IORESOURCE_REG resource
type and parsing the *reg* properties for non-translatable addresses are
feasible. And also does it acceptable by community and OF platform
maintainers.

The use case is actually very different from of_address_to_resource or
of_get_address() because those APIs explicitly return physical memory
addresses from the CPU perspective. It makes more sense to create a new
API that doesn't attempt to translate the reg address. Alternately, a
new API that only translates upto a given parent node.

You don't want to automagically translate as far up the tree as
possible because the code won't know what node the address is associated
with. Translated addresses only make sense if the node it was translated
to as also known.

g.

quoted

How about modifying of_get_address() rather than
__of_address_to_resource() instead? You could introduce
a new of_bus entry for each bus you expect to return
an IORESOURCE_REG, or you could change of_bus_default_get_flags
to return IORESOURCE_REG if the parent node has no ranges property
and is not the root node.

IMO the clearer solution is to introduce a new of_bus bus. In that case
one possible problem will be how to distinguish the non-translatable and
the other buses. Also the *device_type* property is deprecated for non
PCI devices.

The second option will need to change the prototype of .get_flags method
to receive device_node structure.

Thoughts?

-- 
regards,
Stan