Messages in this thread | ![/](/images/icornerl.gif) | | Date | Sun, 14 Jun 2015 08:29:52 -0700 | From | Guenter Roeck <> | Subject | Re: [RFC/RFT PATCH v2] PCI: move pci_read_bridge_bases to the generic PCI layer |
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On 06/13/2015 02:12 AM, Lorenzo Pieralisi wrote: > On Sat, Jun 13, 2015 at 02:47:55AM +0100, Guenter Roeck wrote: >> On Tue, Jun 09, 2015 at 10:01:45AM +0100, Lorenzo Pieralisi wrote: >>> When a PCI bus is scanned, upon PCI bridge detection the kernel >>> has to read the bridge registers to set-up its resources so that >>> the PCI resource hierarchy can be validated properly. >>> >>> Most if not all architectures read PCI bridge registers in the >>> pcibios_fixup_bus hook, that is called by the PCI generic layer >>> whenever a PCI bus is scanned. >>> >>> Since pci_read_bridge_bases is an arch agnostic operation (and it >>> is carried out on all architectures) it can be moved to the generic >>> PCI layer in order to consolidate code and remove the respective >>> calls from the architectures back-ends. >>> >>> The PCI_PROBE_ONLY flag is not checked before calling >>> pci_read_bridge_buses in the generic layer since reading the bridge >>> bases is not related to resources assignment; this implies that it >>> can be carried out safely on PCI_PROBE_ONLY systems too and should >>> not affect architectures (alpha, mips) that check the PCI_PROBE_ONLY >>> flag before reading the bridge bases. >>> >>> In order to validate the resource hierarchy as soon as the resources >>> themselves are probed (ie read from the bridge), this patch also adds >>> code to pci_read_bridge_bases that claims the bridge resources, so that >>> they are validated and inserted in the resource hierarchy as soon as >>> the bridge bases are probed. >>> >> >> Hi Lorenzo, >> >> on one of our systems, I see a lot of messages with your patch applied. >> >> bart kernel: pci 0000:b0:00.0: can't claim BAR 7 [io 0x0000-0x0fff]: no compatible bridge window >> bart kernel: pci 0000:b0:00.0: can't claim BAR 8 [mem 0x94000000-0x941fffff]: no compatible bridge window >> bart kernel: pci 0000:b1:03.0: can't claim BAR 7 [io 0x0000-0x0fff]: no compatible bridge window >> bart kernel: pci 0000:b1:03.0: can't claim BAR 8 [mem 0x95800000-0x959fffff]: no compatible bridge window >> >> and so on. The final IO memory assignment is the same, though, >> before and after your patch. >> >> 95800000-95bfffff : PCI Bus 0000:b0 >> 95800000-959fffff : PCI Bus 0000:b1 >> 95800000-959fffff : PCI Bus 0000:b2 >> 95a00000-95a3ffff : 0000:b0:00.0 >> >> >> Does that have any relevance or is it just nuisance messages ? > > Yes, I knew this could happen. It should be just nuisance messages, > since we are claming bridge resources even on systems where they > are reassigned. We should remove those messages, this means that I > have to craft a function that claims resources without spitting too > much unwanted noise, I can't use pci_claim_bridge_resource for this > purpose as you have noticed, unless I refactor it, open to suggestions > (we claim bridge resources by default, regardless of PROBE_ONLY flag). > > Thanks a lot for testing it, appreciated, I will prepare a v3. >
Hi Lorenzo,
There is no need for v3 because of this. My patch set addresses the BAR 7 message, and the BAR 8 message is actually warranted since the memory window on the upstream port is too small.
Guenter
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