On Mon, Aug 11, 2025 at 08:26:11PM -0700, Lizhi Hou wrote: > On 8/11/25 01:42, Lorenzo Pieralisi wrote: > > > Hi Lizhi, Rob, > > > > while debugging something unrelated I noticed two issues > > (related) caused by the automatic generation of device nodes > > for PCI bridges. > > > > GICv5 interrupt controller DT top level node [1] does not have a "reg" > > property, because it represents the top level node, children (IRSes and ITSs) > > are nested. > > > > It does provide #address-cells since it has child nodes, so it has to > > have a "ranges" property as well. > > > > You have added code to automatically generate properties for PCI bridges > > and in particular this code [2] creates an interrupt-map property for > > the PCI bridges (other than the host bridge if it has got an OF node > > already). > > > > That code fails on GICv5, because the interrupt controller node does not > > have a "reg" property (and AFAIU it does not have to - as a matter of > > fact, INTx mapping works on GICv5 with the interrupt-map in the > > host bridge node containing zeros in the parent unit interrupt > > specifier #address-cells). > Does GICv5 have 'interrupt-controller' but not 'interrupt-map'? I think > of_irq_parse_raw will not check its parent in this case. But that's not the problem. GICv5 does not have an interrupt-map, the issue here is that GICv5 _is_ the parent and does not have a "reg" property. Why does the code in [2] check the reg property for the parent node while building the interrupt-map property for the PCI bridge ? > > It is not clear to me why, to create an interrupt-map property, we > > are reading the "reg" value of the parent IC node to create the > > interrupt-map unit interrupt specifier address bits (could not we > > just copy the address in the parent unit interrupt specifier reported > > in the host bridge interrupt-map property ?). > > > > - #address-cells of the parent describes the number of address cells of > > parent's child nodes not the parent itself, again, AFAIK, so parsing "reg" > > using #address-cells of the parent node is not entirely correct, is it ? > > - It is unclear to me, from an OF spec perspective what the address value > > in the parent unit interrupt specifier ought to be. I think that, at > > least for dts including a GICv3 IC, the address values are always 0, > > regardless of the GICv3 reg property. > > > > I need your feedback on this because the automatic generation must > > work seamlessly for GICv5 as well (as well as all other ICs with no "reg" > > property) and I could not find anything in the OF specs describing > > how the address cells in the unit interrupt specifier must be computed. > > Please see: https://devicetree-specification.readthedocs.io/en/latest/chapter2-devicetree-basics.html > > 2.4.3.1 mentions: > > "Both the child node and the interrupt parent node are required to have > #address-cells and #interrupt-cells properties defined. If a unit address > component is not required, #address-cells shall be explicitly defined to be > zero." Yes, but again, that's not what I am asking. GICv5 requires #address-cells (2.3.5 - link above - it has child nodes and it has to define "ranges") but it does not require a "reg" property, code in [2] fails. That boils down to what does "a unit address component is not required" means. Why does the code in [2] read "reg" to build the parent unit interrupt specifier (with #address-cells size of the parent, which, again, I don't think it is correct) ? > > I found this [3] link where in section 7 there is an interrupt mapping > > algorithm; I don't understand it fully and I think it is possibly misleading. > > > > Now, the failure in [2] (caused by the lack of a "reg" property in the > > IC node) triggers an interrupt-map property generation failure for PCI > > bridges that are upstream devices that need INTx swizzling. > > > > In turn, that leads to a kmemleak detection: > > > > unreferenced object 0xffff000800368780 (size 128): > > comm "swapper/0", pid 1, jiffies 4294892824 > > hex dump (first 32 bytes): > > f0 b8 34 00 08 00 ff ff 04 00 00 00 00 00 00 00 ..4............. > > 70 c2 30 00 08 00 ff ff 00 00 00 00 00 00 00 00 p.0............. > > backtrace (crc 1652b62a): > > kmemleak_alloc+0x30/0x3c > > __kmalloc_cache_noprof+0x1fc/0x360 > > __of_prop_dup+0x68/0x110 > > of_changeset_add_prop_helper+0x28/0xac > > of_changeset_add_prop_string+0x74/0xa4 > > of_pci_add_properties+0xa0/0x4e0 > > of_pci_make_dev_node+0x198/0x230 > > pci_bus_add_device+0x44/0x13c > > pci_bus_add_devices+0x40/0x80 > > pci_host_probe+0x138/0x1b0 > > pci_host_common_probe+0x8c/0xb0 > > platform_probe+0x5c/0x9c > > really_probe+0x134/0x2d8 > > __driver_probe_device+0x98/0xd0 > > driver_probe_device+0x3c/0x1f8 > > __driver_attach+0xd8/0x1a0 > > > > I have not grokked it yet but it seems genuine, so whatever we decide > > in relation to "reg" above, this ought to be addressed too, if it > > is indeed a memleak. > > Not sure what is the leak. I will look into more. Thanks, Lorenzo > > > Lizhi > > > > > Please let me know if something is unclear I can provide further > > details. > > > > Thanks, > > Lorenzo > > > > [1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/log/Documentation/devicetree/bindings/interrupt-controller/arm,gic-v5.yaml?h=v6.17-rc1 > > [2] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/pci/of_property.c?h=v6.17-rc1#n283 > > [3] https://www.devicetree.org/open-firmware/practice/imap/imap0_9d.html
