Comment 0 for bug 1763817

[Impact]
On ARM64 systems enabling cppccontrol=1 in firmware, the dmesg fills with messages like:
[ 4083.960332] ACPI CPPC: PCC check channel failed. Status=0
[ 4085.546975] ACPI CPPC: PCC check channel failed. Status=0
[ 4113.939921] ACPI CPPC: PCC check channel failed. Status=0
[ 4115.531777] ACPI CPPC: PCC check channel failed. Status=0

[Fix]
upstream commit fixes this issue:
commit 3d41386d556db9f720e00de3e11e45f39cb5071c
Author: George Cherian <email address hidden>
Date: Fri Mar 23 03:30:31 2018 -0700

    cpufreq: CPPC: Use transition_delay_us depending transition_latency

[Testing]
-- before kernel patch --
[ 85.969952] ACPI CPPC: PCC check channel failed. Status=0
[ 81.888445] cloud-init[4810]: Cloud-init v. 18.2 running 'modules:final' at Fri, 13 Apr 2018 19:11:57 +0000. Up 80.71 seconds.
[ 81.888625] cloud-init[4810]: Cloud-init v. 18.2 finished at Fri, 13 Apr 2018 19:11:58 +0000. Datasource DataSourceMAAS [http://10.228.68.5:5240/MAAS/metadata/]. Up 81.69 seconds
[ OK ] Started Execute cloud user/final scripts.
[ OK ] Reached target Cloud-init target.
[ 86.230432] ACPI CPPC: PCC check channel failed. Status=0
[ 86.701943] ACPI CPPC: PCC check channel failed. Status=0
[ 86.773668] ACPI CPPC: PCC check channel failed. Status=0
[ 87.369958] ACPI CPPC: PCC check channel failed. Status=0
[ 87.733361] ACPI CPPC: PCC check channel failed. Status=0
[ 88.207372] ACPI CPPC: PCC check channel failed. Status=0

-- after kernel patch --