On Thu, Nov 06, 2014 at 07:46:33PM +0000, Rob Herring wrote:
> On Thu, Nov 6, 2014 at 9:30 AM, Liviu Dudau <Liviu.Dudau@xxxxxxx> wrote:
> > On Thu, Nov 06, 2014 at 02:57:35PM +0000, Rob Herring wrote:
> >> On Thu, Nov 6, 2014 at 4:05 AM, Liviu Dudau <Liviu.Dudau@xxxxxxx> wrote:
> >> > On Wed, Nov 05, 2014 at 11:17:43PM +0000, Bjorn Helgaas wrote:
> >> >> On Tue, Nov 04, 2014 at 12:47:40PM +0100, Lucas Stach wrote:
> >> >> > This property was added by 41e5c0f81d3e
> >> >> > (of/pci: Add pci_get_new_domain_nr() and of_get_pci_domain_nr())
> >> >> > without the required binding documentation. As this property
> >> >> > will be supported by a number of host bridge drivers going forward,
> >> >> > add it to the common PCI binding doc.
> >> >> >
> >> >> > Signed-off-by: Lucas Stach <l.stach@xxxxxxxxxxxxxx>
> >> >>
> >> >> I merged 41e5c0f81d3e through my tree, and I could merge something like
> >> >> this if a consensus develops with some acks. But I'll just let you guys
> >> >> handle it unless you poke me again.
> >> >
> >> > While I think the "linux,pci-domain" property *must* be documented, I
> >> > would like to get a consensus first on the usage. If we agree that
> >> > the property is mandatory to all host bridge drivers that use OF then
> >> > we need to patch existing drivers (partially done through Lorenzo's
> >> > patches, but other arches are ignoring it). If we say all *new* drivers
> >> > need to use it then we also need to come up with a strategy on how to
> >> > deal with old vs new school drivers.
> >> >
> >> > My preferred approach is the 3rd way: "linux,pci-domain" becomes part of
> >> > the core PCI infrastructure (and we find the common ground with ACPI).
> >> > That way the host bridge drivers don't have to do anything, but the DT
> >> > creators have to specify a value.
> >>
> >> I'm okay with it being in the core. It was the mixture of using the
> >> property and automatic numbering that I had issues with. Any mixture
> >> whether in DT or in drivers should be an error. Also, I think having a
> >> mixture of root bus host drivers would be rare, so I'm not too
> >> concerned about some drivers supporting the property and others not.
> >> In any case, these issues are all with the kernel and not really the
> >> concern for the binding. For the binding, simply all hosts set the
> >> domain or none of them do.
> >
> > Repeating what you've said to verify my understanding: you are OK with
> > the "linux,pci-domain" being handled in the PCI framework and mandatory
> > to all OF-based host bridges and architectures. Failure to include
> > the property should be an error and no host bridge driver should default
> > to the auto-generation of domain numbers.
> >
> > Is that correct?
>
> Not exactly. It is only mandatory when you have multiple root buses.
> But we can't say an existing dtb is in error, so it has to remain
> optional for compatibility. Also, given it is a Linux property, you
> can't really say it is mandatory for all PCI bindings from a DT
> perspective.
>
> While we could have issues in theory if this is handled in the
> drivers, I don't think we will in practice as having root buses with
> different drivers is unlikely.
That's correct. However, I would like to bring to you attention that as
long as the property is treated as optional in certain cases we will need,
in the framework code, to mix the assignment of a domain number coming from
parsing of the property with the auto-numbering scheme in order to support
old DT files. And that was one of your major concerns when reviewing the
series. Any suggestions or clarifications?
Best regards,
Liviu
>
> Rob
>
--
====================
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| fix the world, |
| but they're not |
| giving me the |
\ source code! /
---------------
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