On Fri, Mar 08, 2013 at 05:12:04PM -0600, Rob Herring wrote:
> On 03/08/2013 01:14 AM, Thierry Reding wrote:
> > On Thu, Mar 07, 2013 at 06:05:33PM -0600, Rob Herring wrote:
> >> On 03/07/2013 02:47 PM, Thierry Reding wrote:
> > [...]
> >>> In a nutshell (since some of the context isn't quoted anymore) the
> >>> problem that we're trying to solve is that some of the embedded SoCs
> >>> require per-root-port registers for configuration. The PCI DT
> >>> specification doesn't make any provisions for this. A few alternatives
> >>> have been discussed so far:
> >>
> >> I'm not sure I follow. This is different than the host controller
> >> registers? Why would this not just be multiple entries in the reg property?
> >
> > Well the register regions are per root-port. On Tegra20 there's 2 of
> > them, Tegra30 has 3 and if I understand correctly Marvell can have up to
> > 10 (!). Adding all of them to the reg property of the host controller
> > could work but it needs some way to match the reg entry to the root port
> > similar to option 1 below.
>
> The compatible property of the PCI host controller can imply what each
> index of the reg property entries is for.
>
> >
> > Adding a property in the root port nodes seems like a cleaner and more
> > accurate representation of the hardware to me, but if that's not
> > acceptable perhaps we need to bite the bullet and add the code to look
> > the registers up from the parent's reg property.
>
> What I don't like is a new property defined to describe mmio addresses.
> We already have a property for that and it is "reg".
Okay, understood.
> But I think I'm still missing something:
>
> >>> pci@0,1 {
> >>> ...
> >>> reg = <0x00000800 0 0 0 0>;
>
> Is this a PCI bus address?
Yes. The example is slightly wrong. pci@0,1 should actually be pci@1,0.
That means it is device 1, function 0 on the bus (implicitly 0 in this
case). That matches the values in the reg property, whose first cell is
defined as follows, quoting the PCI OF specification:
npt000ss bbbbbbbb dddddfff rrrrrrrr
Where:
n is 0 if the address is relocatable, 1 otherwise
p is 1 if the addressable region is "prefetchable", 0
otherwise
t is 1 if the address is aliased (for non-relocatable
I/O), below 1 MB (for Memory), or below 64 KB (for
relocatable I/O).
ss is the space code, denoting the address space
bbbbbbbb is the 8-bit Bus Number
ddddd is the 5-bit Device Number
fff is the 3-bit Function Number
rrrrrrrr is the 8-bit Register Number
Thierry
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