[Intel-wired-lan] regression in igb driver from commit 182785335447

[Michal Kubecek]

one of my colleagues observed a regression in recent 4.4.x kernels on
one of test machines with 82575EB NIC (rev 02, 8086:10a7, firmware
version 1.6.5). On boot, first port fails to initialize and only the net
device for second is created. Kernel log looks like

[   13.710535] igb: Intel(R) Gigabit Ethernet Network Driver - version 5.4.0-k
[   13.710538] igb: Copyright (c) 2007-2014 Intel Corporation.
[   13.710584] igb 0000:08:00.0: PCI->APIC IRQ transform: INT A -> IRQ 56
[   13.712126] igb: probe of 0000:08:00.0 failed with error -2
[   13.712152] igb 0000:08:00.1: PCI->APIC IRQ transform: INT B -> IRQ 70
[   13.904537] igb 0000:08:00.1: Intel(R) Gigabit Ethernet Network Connection
[   13.904545] igb 0000:08:00.1: eth0: (PCIe:2.5Gb/s:Width x4) 00:30:48:7b:5d:37
[   13.904547] igb 0000:08:00.1: eth0: PBA No: Unknown
[   13.904556] igb 0000:08:00.1: Using MSI-X interrupts. 4 rx queue(s), 4 tx queue(s)
[   13.927029] igb 0000:08:00.1 eth1: renamed from eth0

Checking the changelog led us to a stable-4.4.y backport of mainline
commit 182785335447 ("igb: reset the PHY before reading the PHY ID") as
the most promising suspect and reverting it fixed the issue.

I also reproduced the issue with 4.15 kernel, except this time both
ports of the card failed to probe:

[   16.826649] igb: Intel(R) Gigabit Ethernet Network Driver - version 5.4.0-k
[   16.840784] igb: Copyright (c) 2007-2014 Intel Corporation.
[   16.852176] igb 0000:08:00.0: PCI->APIC IRQ transform: INT A -> IRQ 56
[   16.867919] igb: probe of 0000:08:00.0 failed with error -2
[   16.879254] igb 0000:08:00.1: PCI->APIC IRQ transform: INT B -> IRQ 70
[   16.898178] igb: probe of 0000:08:00.1 failed with error -2

Reverting commit 182785335447 fixed the issue here as well.

Michal Kubecek