phy: marvell: phy-mvebu-cp110-comphy: link failure and lockup built as module (=M)

[Josua Mayer]

Dear Maintainers,

I came across a bug srelating to cp110 comphy driver.

On a board with CN9130 SoC + 2 external CPs Debian 13 freezes during boot,
at some point after initramfs and kernel module loading has started.

This occurs only when a pci card is present and had link-up from u-boot, e.g.:

PCIE-0: Link up (Gen3-x4, Bus0)
PCIE-12: Link up (Gen3-x1, Bus12)

The issue is reproducible with a generic rootfs, kernel built with arm64 defconfig,
no initramfs, but a single kernel configuration change:

CONFIG_PHY_MVEBU_CP110_COMPHY=y -> m

i.e. building the comphy driver as a module.

The problem shows up usually by the console freezing during boot,
before eventually the system watchdog hard resets SoC.

[1] below shows the pci kernel messages during probe of the x4 port on my board,
with the comphy driver builtin. After this log I reach login prompt and the system
works as intended.
[2] shows the pci messages for same port with comphy as a module. After the final
line the systemd hard reset once watchdog expired.
Both logs were captured on v6.12.48, but I did reproduce the problem with v6.18-rc1 too.
For reference I am attaching full console logs as files to this mail.

Most notably in the error case we get "Phy link never came up".
Perhaps when comphy is a module some clock is stopped before pci probe starts ...
and after pci probe function completes it locks up the controller that actually had a link,
even though kernel driver did not detect.

[1]
[    1.995477] armada8k-pcie f2600000.pcie: armada8k_pcie_probe start
[    2.104941] armada8k-pcie f2600000.pcie: host bridge /cp0/pcie at f2600000 ranges:
[    2.112319] armada8k-pcie f2600000.pcie:      MEM 0x00c0000000..0x00dfefffff -> 0x00c0000000
[    2.120841] armada8k-pcie f2600000.pcie: iATU: unroll F, 8 ob, 8 ib, align 64K, limit 4G
[    2.232055] armada8k-pcie f2600000.pcie: PCIe Gen.3 x4 link up
[    2.238103] armada8k-pcie f2600000.pcie: PCI host bridge to bus 0000:00
[    2.244760] pci_bus 0000:00: root bus resource [bus 00-ff]
[    2.250282] pci_bus 0000:00: root bus resource [mem 0xc0000000-0xdfefffff]
[    2.257213] pci 0000:00:00.0: [11ab:0110] type 01 class 0x060400 PCIe Root Port
[    2.264559] pci 0000:00:00.0: BAR 0 [mem 0x00000000-0x000fffff]
[    2.270516] pci 0000:00:00.0: PCI bridge to [bus 01-ff]
[    2.275773] pci 0000:00:00.0:   bridge window [mem 0xc0000000-0xc00fffff]
[    2.282643] pci 0000:00:00.0: supports D1 D2
[    2.286937] pci 0000:00:00.0: PME# supported from D0 D1 D3hot
[    2.294292] pci 0000:01:00.0: [144d:a804] type 00 class 0x010802 PCIe Endpoint
[    2.301669] pci 0000:01:00.0: BAR 0 [mem 0xc0000000-0xc0003fff 64bit]
[    2.316143] pci 0000:00:00.0: BAR 0 [mem 0xc0000000-0xc00fffff]: assigned
[    2.322972] pci 0000:00:00.0: bridge window [mem 0xc0100000-0xc01fffff]: assigned
[    2.330495] pci 0000:01:00.0: BAR 0 [mem 0xc0100000-0xc0103fff 64bit]: assigned
[    2.337887] pci 0000:00:00.0: PCI bridge to [bus 01-ff]
[    2.343142] pci 0000:00:00.0:   bridge window [mem 0xc0100000-0xc01fffff]
[    2.349968] pci_bus 0000:00: resource 4 [mem 0xc0000000-0xdfefffff]
[    2.356267] pci_bus 0000:01: resource 1 [mem 0xc0100000-0xc01fffff]
[    2.362778] pcieport 0000:00:00.0: PME: Signaling with IRQ 62
[    2.368745] pcieport 0000:00:00.0: AER: enabled with IRQ 62
[    2.374447] armada8k-pcie f2600000.pcie: armada8k_pcie_probe end

[2]
[   17.356469] armada8k-pcie f2600000.pcie: armada8k_pcie_probe start
[   17.444656] armada8k-pcie f2600000.pcie: host bridge /cp0/pcie at f2600000 ranges:
[   17.452042] armada8k-pcie f2600000.pcie:      MEM 0x00c0000000..0x00dfefffff -> 0x00c0000000
[   17.460572] armada8k-pcie f2600000.pcie: iATU: unroll F, 8 ob, 8 ib, align 64K, limit 4G
[   18.427718] armada8k-pcie f2600000.pcie: Phy link never came up
[   18.433776] armada8k-pcie f2600000.pcie: PCI host bridge to bus 0006:00
[   18.440445] pci_bus 0006:00: root bus resource [bus 00-ff]
[   18.445968] pci_bus 0006:00: root bus resource [mem 0xc0000000-0xdfefffff]

I am a bit lost here in how to further debug this - kindly share some ideas if you have any.

sincerely
Josua Mayer
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