[PATCH v6 00/21] MBus DT binding: PCIe strikes back

Arnd Bergmann arnd at arndb.de
Fri Jul 5 18:54:22 EDT 2013

On Saturday 06 July 2013, Jason Gunthorpe wrote:
> This is a good try, but this coding doesn't work...
> Recall the long discussion that came up during the original
> development of this binding. The OF spec says this:
>  In particular, the phys.hi fields of the child address spaces in the
>  "ranges" property for PCI does not contain
>  the same information as "reg" property entries within PCI nodes. The
>  only information that is present in
>  "ranges" phys.hi entries are the non-relocatable, prefetchable and
>  the PCI address space bits for which the en-
>  try applies. I.e., only the n, p and ss bits are present; the
>  bbbbbbbb, ddddd, fff and rrrrrrrr fields are 0.
>  When an address is to be mapped through a PCI bus bridge node, the
>  phys.hi value of the address to be mapped
>  and the child field of a "ranges" entry should be masked so that only
>  the ss bits are compared. I.e., the only
>  portion of phys.hi that should participate in the range determination
>  is the address space indicator (the ss bits).
> Which forbids (0x82000800 .. ..) from being in a ranges

ah, and I thought Ezequiel was being more clever than what I had suggested

> I don't have an idea how to encode MBUS_ID in the PCI-E ranges :(
> Arnd? Didn't you have some idea?

The way I described it during the last review, I suggested using
the middle cell of the PCI address here. Since the PCIe port
is 32 bit only, it's otherwise unused. We can do one of two things

a) put the port number in the second cell

   0x82000000 1 0xe0000000 MBUS_ID(0x04, 0xe8) 0xe0000000 0 0x08000000 /* Port 0.0 MEM */
   0x82000000 2 0xe0000000 MBUS_ID(0x04, 0xe9) 0xe0000000 0 0x08000000 /* Port 1.0 MEM */

b) translate the entire MBUS space here

   0x82000000 0 0 0 0 0x1000000 0 /* all MBUS_IDs */

In both cases, the individual ports would have another non-empty
ranges property

   0x82000000 1 0xe0000000 0x82000000 0 0xe0000000 0x08000000 /* ranges for port 0.0 */

   0x82000000 MBUS_ID(0x04, 0xe8) 0xe0000000 0x82000000 0 0xe0000000 0 0x08000000

I left out the change I suggested in my other reply to not describe
the aperture in this node but translate the entire 4GB space.


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