Messages in this thread | | | From | "Chalamarla, Tirumalesh" <> | Subject | Re: [PATCH 1/4] arm64: gicv3: its: Encode domain number in PCI stream id | Date | Fri, 22 May 2015 22:57:40 +0000 |
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> On May 22, 2015, at 1:26 AM, Marc Zyngier <marc.zyngier@arm.com> wrote: > > On 20/05/15 13:48, Robert Richter wrote: >> Mark, >> >> thanks for review, also of the other patches of this series. >> >> See below >> >> On 20.05.15 13:11:38, Marc Zyngier wrote: >>>> - dev_alias->dev_id = alias; >>>> + dev_alias->dev_id = (pci_domain_nr(pdev->bus) << 16) | alias; >> >>> This feels very scary. We're now assuming that the domain number will >>> always be presented to the doorbell. What guarantee do we have that >>> this is always the case, irrespective of the platform? >>> >>> Also, domains have no PCI reality, they are a Linux thing. And they can >>> be "randomly" assigned, unless you force the domain in DT with a >>> linux,pci-domain property. This looks even more wrong, specially >>> considering ACPI. >> >> The main problem here is that device ids (32 bits) are system >> specific. Since we have more than one PCI root complex we need the >> upper 16 bits in the devid for mapping. Using pci_domain_nr for this >> fits our needs for now and shouldn't affect systems with a single RC >> only as the domain nr is zero then. >> >> The domain number is incremented during initialization beginnig with >> zero and the order of it is fixed since it is taken from DT or ACPI >> tables. So we have full controll of it. I don't see issues here. > > This may match what you have on ThunderX (as long as the kernel doesn't > adopt another behaviour when allocating the domain number). But other > platforms may have a completely different numbering, which will mess > them up entirely. > >>> It really feels like we need a way to describe how the BDF numbering is >>> augmented. We also need to guarantee that we get the actual bridge >>> number, as opposed to the domain number. >> >> But true, the obove is just intermediate. In the end we need some sort >> of handler that is setup during cpu initialization that registers a >> callback for the gic to determine the device id of that paricular >> system. > > I don't really like the idea of a callback from the GIC - I'd prefer it > to be standalone, and rely on the topology information to build the > DeviceID. Mark Rutland had some ideas for DT (he posted an RFC a while > ago), maybe it would be good to get back to that and find out what we > can do. ACPI should also have similar information (IORT?). >
How can some one pass this from DT, especially in GIC entry. i still think it is bus owner responsibility and call back is better idea. but if some one has a better idea for DT and ACPI, we are fine as long as it works on ThunderX.
Thanks, Tirumalesh.
> Thanks, > > M. > -- > Jazz is not dead. It just smells funny...
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