Hi,
On Thu, Apr 11, 2024 at 8:01 AM Krzysztof Kozlowski
<krzysztof.kozlowski@xxxxxxxxxx> wrote:
>
> On 10/04/2024 23:26, Bjorn Helgaas wrote:
> > On Wed, Apr 10, 2024 at 08:15:19PM +0200, Krzysztof Kozlowski wrote:
> >> MT7621 PCI host bridge has children which apparently are also PCI host
> >> bridges, at least that's what the binding suggest.
> >
> > What does it even mean for a PCI host bridge to have a child that is
> > also a PCI host bridge?
> >
> > Does this mean a driver binds to the "parent" host bridge, enumerates
> > the PCI devices below it, and finds a "child" host bridge?
Yes, that is exactly what you can see on enumeration.
The following is a typical boot trace where all bridges has a device also below:
[ 20.927280] mt7621-pci 1e140000.pcie: host bridge /pcie@1e140000 ranges:
[ 20.940675] mt7621-pci 1e140000.pcie: No bus range found for
/pcie@1e140000, using [bus 00-ff]
[ 20.958228] mt7621-pci 1e140000.pcie: MEM
0x0060000000..0x006fffffff -> 0x0060000000
[ 20.974566] mt7621-pci 1e140000.pcie: IO
0x001e160000..0x001e16ffff -> 0x0000000000
[ 21.369711] mt7621-pci 1e140000.pcie: PCIE0 enabled
[ 21.379316] mt7621-pci 1e140000.pcie: PCIE1 enabled
[ 21.389140] mt7621-pci 1e140000.pcie: PCIE2 enabled
[ 21.399014] PCI coherence region base: 0x60000000, mask/settings: 0xf0000002
[ 21.413343] mt7621-pci 1e140000.pcie: PCI host bridge to bus 0000:00
[ 21.425952] pci_bus 0000:00: root bus resource [bus 00-ff]
[ 21.437023] pci_bus 0000:00: root bus resource [mem 0x60000000-0x6fffffff]
[ 21.450657] pci_bus 0000:00: root bus resource [io 0x0000-0xffff]
[ 21.462960] pci 0000:00:00.0: [0e8d:0801] type 01 class 0x060400
[ 21.474832] pci 0000:00:00.0: reg 0x10: [mem 0x00000000-0x7fffffff]
[ 21.487255] pci 0000:00:00.0: reg 0x14: [mem 0x00000000-0x0000ffff]
[ 21.499807] pci 0000:00:00.0: supports D1
[ 21.507625] pci 0000:00:00.0: PME# supported from D0 D1 D3hot
[ 21.519923] pci 0000:00:01.0: [0e8d:0801] type 01 class 0x060400
[ 21.531827] pci 0000:00:01.0: reg 0x10: [mem 0x00000000-0x7fffffff]
[ 21.544225] pci 0000:00:01.0: reg 0x14: [mem 0x00000000-0x0000ffff]
[ 21.556773] pci 0000:00:01.0: supports D1
[ 21.564621] pci 0000:00:01.0: PME# supported from D0 D1 D3hot
[ 21.576823] pci 0000:00:02.0: [0e8d:0801] type 01 class 0x060400
[ 21.588726] pci 0000:00:02.0: reg 0x10: [mem 0x00000000-0x7fffffff]
[ 21.601128] pci 0000:00:02.0: reg 0x14: [mem 0x00000000-0x0000ffff]
[ 21.613668] pci 0000:00:02.0: supports D1
[ 21.621520] pci 0000:00:02.0: PME# supported from D0 D1 D3hot
[ 21.634850] pci 0000:00:00.0: bridge configuration invalid ([bus
00-00]), reconfiguring
[ 21.650699] pci 0000:00:01.0: bridge configuration invalid ([bus
00-00]), reconfiguring
[ 21.666571] pci 0000:00:02.0: bridge configuration invalid ([bus
00-00]), reconfiguring
[ 21.682825] pci 0000:01:00.0: [1b21:0611] type 00 class 0x010185
[ 21.694707] pci 0000:01:00.0: reg 0x10: [io 0x0000-0x0007]
[ 21.705725] pci 0000:01:00.0: reg 0x14: [io 0x0000-0x0003]
[ 21.716789] pci 0000:01:00.0: reg 0x18: [io 0x0000-0x0007]
[ 21.727843] pci 0000:01:00.0: reg 0x1c: [io 0x0000-0x0003]
[ 21.738907] pci 0000:01:00.0: reg 0x20: [io 0x0000-0x000f]
[ 21.749979] pci 0000:01:00.0: reg 0x24: [mem 0x00000000-0x000001ff]
[ 21.762568] pci 0000:01:00.0: 2.000 Gb/s available PCIe bandwidth,
limited by 2.5 GT/s PCIe x1 link at 0000:00:00.0 (capable of 4.000
Gb/s with 5.0 GT/s PCIe x1 link)
[ 21.819657] pci 0000:00:00.0: PCI bridge to [bus 01-ff]
[ 21.829966] pci 0000:00:00.0: bridge window [io 0x0000-0x0fff]
[ 21.842054] pci 0000:00:00.0: bridge window [mem 0x00000000-0x000fffff]
[ 21.855532] pci 0000:00:00.0: bridge window [mem
0x00000000-0x000fffff pref]
[ 21.869874] pci_bus 0000:01: busn_res: [bus 01-ff] end is updated to 01
[ 21.883352] pci 0000:02:00.0: [1b21:0611] type 00 class 0x010185
[ 21.895230] pci 0000:02:00.0: reg 0x10: [io 0x0000-0x0007]
[ 21.906256] pci 0000:02:00.0: reg 0x14: [io 0x0000-0x0003]
[ 21.917309] pci 0000:02:00.0: reg 0x18: [io 0x0000-0x0007]
[ 21.928373] pci 0000:02:00.0: reg 0x1c: [io 0x0000-0x0003]
[ 21.939428] pci 0000:02:00.0: reg 0x20: [io 0x0000-0x000f]
[ 21.950500] pci 0000:02:00.0: reg 0x24: [mem 0x00000000-0x000001ff]
[ 21.963094] pci 0000:02:00.0: 2.000 Gb/s available PCIe bandwidth,
limited by 2.5 GT/s PCIe x1 link at 0000:00:01.0 (capable of 4.000
Gb/s with 5.0 GT/s PCIe x1 link)
[ 22.029662] pci 0000:00:01.0: PCI bridge to [bus 02-ff]
[ 22.039993] pci 0000:00:01.0: bridge window [io 0x0000-0x0fff]
[ 22.052063] pci 0000:00:01.0: bridge window [mem 0x00000000-0x000fffff]
[ 22.065538] pci 0000:00:01.0: bridge window [mem
0x00000000-0x000fffff pref]
[ 22.079886] pci_bus 0000:02: busn_res: [bus 02-ff] end is updated to 02
[ 22.093352] pci 0000:03:00.0: [1b21:0611] type 00 class 0x010185
[ 22.105233] pci 0000:03:00.0: reg 0x10: [io 0x0000-0x0007]
[ 22.116249] pci 0000:03:00.0: reg 0x14: [io 0x0000-0x0003]
[ 22.127313] pci 0000:03:00.0: reg 0x18: [io 0x0000-0x0007]
[ 22.138367] pci 0000:03:00.0: reg 0x1c: [io 0x0000-0x0003]
[ 22.149451] pci 0000:03:00.0: reg 0x20: [io 0x0000-0x000f]
[ 22.160503] pci 0000:03:00.0: reg 0x24: [mem 0x00000000-0x000001ff]
[ 22.173091] pci 0000:03:00.0: 2.000 Gb/s available PCIe bandwidth,
limited by 2.5 GT/s PCIe x1 link at 0000:00:02.0 (capable of 4.000
Gb/s with 5.0 GT/s PCIe x1 link)
[ 22.239653] pci 0000:00:02.0: PCI bridge to [bus 03-ff]
[ 22.249973] pci 0000:00:02.0: bridge window [io 0x0000-0x0fff]
[ 22.262045] pci 0000:00:02.0: bridge window [mem 0x00000000-0x000fffff]
[ 22.275524] pci 0000:00:02.0: bridge window [mem
0x00000000-0x000fffff pref]
[ 22.289870] pci_bus 0000:03: busn_res: [bus 03-ff] end is updated to 03
[ 22.303080] pci 0000:00:00.0: BAR 0: no space for [mem size 0x80000000]
[ 22.316129] pci 0000:00:00.0: BAR 0: failed to assign [mem size 0x80000000]
[ 22.329956] pci 0000:00:01.0: BAR 0: no space for [mem size 0x80000000]
[ 22.343081] pci 0000:00:01.0: BAR 0: failed to assign [mem size 0x80000000]
[ 22.356912] pci 0000:00:02.0: BAR 0: no space for [mem size 0x80000000]
[ 22.370053] pci 0000:00:02.0: BAR 0: failed to assign [mem size 0x80000000]
[ 22.383870] pci 0000:00:00.0: BAR 8: assigned [mem 0x60000000-0x600fffff]
[ 22.397349] pci 0000:00:00.0: BAR 9: assigned [mem
0x60100000-0x601fffff pref]
[ 22.411692] pci 0000:00:01.0: BAR 8: assigned [mem 0x60200000-0x602fffff]
[ 22.425165] pci 0000:00:01.0: BAR 9: assigned [mem
0x60300000-0x603fffff pref]
[ 22.439522] pci 0000:00:02.0: BAR 8: assigned [mem 0x60400000-0x604fffff]
[ 22.452991] pci 0000:00:02.0: BAR 9: assigned [mem
0x60500000-0x605fffff pref]
[ 22.467328] pci 0000:00:00.0: BAR 1: assigned [mem 0x60600000-0x6060ffff]
[ 22.480814] pci 0000:00:01.0: BAR 1: assigned [mem 0x60610000-0x6061ffff]
[ 22.494303] pci 0000:00:02.0: BAR 1: assigned [mem 0x60620000-0x6062ffff]
[ 22.507766] pci 0000:00:00.0: BAR 7: assigned [io 0x0000-0x0fff]
[ 22.519861] pci 0000:00:01.0: BAR 7: assigned [io 0x1000-0x1fff]
[ 22.531960] pci 0000:00:02.0: BAR 7: assigned [io 0x2000-0x2fff]
[ 22.544068] pci 0000:01:00.0: BAR 5: assigned [mem 0x60000000-0x600001ff]
[ 22.557548] pci 0000:01:00.0: BAR 4: assigned [io 0x0000-0x000f]
[ 22.569635] pci 0000:01:00.0: BAR 0: assigned [io 0x0010-0x0017]
[ 22.581726] pci 0000:01:00.0: BAR 2: assigned [io 0x0018-0x001f]
[ 22.593827] pci 0000:01:00.0: BAR 1: assigned [io 0x0020-0x0023]
[ 22.605917] pci 0000:01:00.0: BAR 3: assigned [io 0x0024-0x0027]
[ 22.618030] pci 0000:00:00.0: PCI bridge to [bus 01]
[ 22.627859] pci 0000:00:00.0: bridge window [io 0x0000-0x0fff]
[ 22.639956] pci 0000:00:00.0: bridge window [mem 0x60000000-0x600fffff]
[ 22.653437] pci 0000:00:00.0: bridge window [mem
0x60100000-0x601fffff pref]
[ 22.667785] pci 0000:02:00.0: BAR 5: assigned [mem 0x60200000-0x602001ff]
[ 22.681268] pci 0000:02:00.0: BAR 4: assigned [io 0x1000-0x100f]
[ 22.693359] pci 0000:02:00.0: BAR 0: assigned [io 0x1010-0x1017]
[ 22.705450] pci 0000:02:00.0: BAR 2: assigned [io 0x1018-0x101f]
[ 22.717552] pci 0000:02:00.0: BAR 1: assigned [io 0x1020-0x1023]
[ 22.729654] pci 0000:02:00.0: BAR 3: assigned [io 0x1024-0x1027]
[ 22.741746] pci 0000:00:01.0: PCI bridge to [bus 02]
[ 22.751587] pci 0000:00:01.0: bridge window [io 0x1000-0x1fff]
[ 22.763678] pci 0000:00:01.0: bridge window [mem 0x60200000-0x602fffff]
[ 22.777161] pci 0000:00:01.0: bridge window [mem
0x60300000-0x603fffff pref]
[ 22.791515] pci 0000:03:00.0: BAR 5: assigned [mem 0x60400000-0x604001ff]
[ 22.804991] pci 0000:03:00.0: BAR 4: assigned [io 0x2000-0x200f]
[ 22.817084] pci 0000:03:00.0: BAR 0: assigned [io 0x2010-0x2017]
[ 22.829175] pci 0000:03:00.0: BAR 2: assigned [io 0x2018-0x201f]
[ 22.841274] pci 0000:03:00.0: BAR 1: assigned [io 0x2020-0x2023]
[ 22.853379] pci 0000:03:00.0: BAR 3: assigned [io 0x2024-0x2027]
[ 22.865472] pci 0000:00:02.0: PCI bridge to [bus 03]
[ 22.875312] pci 0000:00:02.0: bridge window [io 0x2000-0x2fff]
[ 22.887403] pci 0000:00:02.0: bridge window [mem 0x60400000-0x604fffff]
>
> I think the question should be towards Mediatek folks. I don't know what
> this hardware is exactly, just looks like pci-pci-bridge. The driver
> calls the children host bridges as "ports".
You can see the topology here in my first driver submit cover letter
message [0].
Thanks,
Sergio Paracuellos
[0]: https://lore.kernel.org/all/CAMhs-H-BA+KzEwuDPzcmrDPdgJBFA2XdYTBvT4R4MEOUB=WQ1g@xxxxxxxxxxxxxx/t/
>
> Best regards,
> Krzysztof
>
