[PATCH 0/3] Add PCI domain support to R-Car drivers

[Liviu Dudau]

On Tue, Sep 23, 2014 at 12:00:41PM +0100, Phil Edworthy wrote:
> Hi Liviu,
> 
> On 23 September 2014 11:32, Liviu wrote:
> > On Tue, Sep 23, 2014 at 11:10:29AM +0100, Phil Edworthy wrote:
> > > Hi Bjorn,
> > >
> > > On 22 September 2014 22:01, Bjorn wrote:
> > > > On Mon, Sep 22, 2014 at 10:51:07AM +0100, Phil Edworthy wrote:
> > > > > The Renesas R-Car devices (r8a7790 and r8a7791) use two PCI controller
> > > > drivers,
> > > > > one for an external PCIe slot, the other for an internal PCI bridge to USB
> > > > > controllers.
> > > > >
> > > > > However, they currently do not work at the same time as they use the
> > > > same PCI
> > > > > domain and use the same root bus number. We can't use different root
> > > > bus numbers
> > > > > due to the way root bus numbers are assigned in pcibios_init_hw() in
> > > > > arch/arm/kernel/bios32.c.
> > > > >
> > > > > Since the two PCI controllers are completely independent, I think it makes
> > > > sense
> > > > > to use different PCI domains for them.
> > > > >
> > > > > I've marked the third patch as RFC as I am not sure of the impact of
> > > > enabling
> > > > > PCI domains for all ARM devices. In the march to 'one kernel to rule them
> > > > all',
> > > > > I steered clear of mach specific changes.
> > > > >
> > > > > These patches require the following patch from Liviu Dudau:
> > > > >   [PATCH v11 07/10] OF: Introduce helper function for getting PCI
> > > > domain_nr
> > > > > Based on comments on this patch from Jason Gunthorpe, there is still the
> > > > issue
> > > > > that the domain numbers may change depending on the ordering at probe
> > > > time.
> > > > > However, this can be fixed later on by adding the entries in the DT files.
> > > > >
> > > > >
> > > > > Phil Edworthy (3):
> > > > >   PCI: rcar-pcie: Add call to get domain nr
> > > > >   PCI: rcar-internal-pci: Add call to get domain nr
> > > > >   ARM: Enable PCI domains
> > > >
> > > > I'm deferring these for now because they depend on Liviu's work, which I
> > > > haven't merged yet, and I suspect some minor adaptation will be required
> > > > here.
> > > >
> > > > For what it's worth, I agree with Rob's hesitation about mixing lookup with
> > > > domain number allocation in of_pci_get_domain_nr().  That seems
> > > > unnecessarily complicated.
> > > I could create patches to add an optional "pci-domain" property for the R-Car
> > > PCI drivers, and just attempt to get the property in the drivers. If not found,
> > > the drivers will assume the domain is 0.
> > >
> > > We would then have fixed PCI domain numbering and I don't have to worry about
> > > Liviu's work.
> > 
> > I will split the current of_pci_get_domain_nr() even further and replace it with
> > two functions: pci_get_domain_nr() which will do just the allocation (still based
> > on the boolean flag passed as parameter) and of_get_pci_domain_nr() that will
> > retrieve a "linux,pci-domain" value from a property belonging to a given device
> > node.
> This doesn't solve the problem of different domain numbers based on different
> probe ordering. If you have multiple domains then I think you must have the
> "linux,pci-domain" property for each controller.

Correct, but I've said I'm going to leave for the moment the check to the host controller(s).
So if you care about ordering or mandating the presence of "linux,pci-domain" in the
DT, please add the check in your driver.

> 
> If we assume the above, of_get_pci_domain_nr() can just return a bus number of
> 0 if the "linux,pci-domain" property doesn't exist.

You mean *domain* number of 0. But that is still a valid value and you won't be able
to distinguish between DT providing a "linux,pci-domain" value of zero and the
property not being present.

> 
> I suppose you could have a temporary solution that allocates the domain numbers
> until the necessary drivers have been updated.

And that is what pci_get_domain_nr() will do. If you don't care about ordering, one
will use that one. If you care about ordering then "linux,pci-domain" is required
and one can use of_get_pci_domain_nr() to retrieve it and fail if the information
is missing.

Does that look like a workable solution?

Best regards,
Liviu

> 
> > I plan to leave for the moment the check for mandatory presence of
> > "linux,pci-domain"
> > to the host bridge driver so that everyone can implement their own policies.
> > 
> > How does that sound?
> 
> Thanks
> Phil

-- 
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