I've also tried the clocksource=acpi_pm as per suggestion from johnnybuoy on #ubuntu+1 IRC channel. The result was:
[0.240000] PCI: Cannot allocate region 7 of bridge 0000:00:05.0 [0.240000] PCI: Cannot allocate region 8 of bridge 0000:00:05.0
I've also tried the clocksource=acpi_pm as per suggestion from johnnybuoy on #ubuntu+1 IRC channel. The result was:
[0.240000] PCI: Cannot allocate region 7 of bridge 0000:00:05.0
[0.240000] PCI: Cannot allocate region 8 of bridge 0000:00:05.0