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