(In reply to Alex Deucher from comment #6)
> (In reply to brett.hassall from comment #5)
> > (In reply to Emil Velikov from comment #2)
> > > If your bisection has gone right, you're looking at either
> > > c39b487f195b93235ee76384427467786f7bf29f (if you're running amdgpu) or
> > > b817634276f7f68c9d1d6d4a27117ff3c2f16956 (if you're on radeon).
> > > 
> > > lspci should tell you which one, and you should be able to revert either one
> > > on top of 4.8.5. Once you confirm the commit causing the issue, please
> > > change the component accordingly and CC the author - Alex Deucher.
> > 
> > Following the "git checkout tags/v4.8-rc3 -b bug" I reverted
> > b817634276f7f68c9d1d6d4a27117ff3c2f16956. Power usage dropped by approx 4.5W
> > (measured after login once system had settled, wifi not connected).
> 
> So apparently your system claims to support pcie pm (d3cold), but either
> doesn't or it's disabled for some reason.

I've taken a look in the BIOS and there doesn't appear to be any settings under
Power Management related to pcie. I've also checked in /etc/default/grub, there
is only 'quiet' on the CMDLINE settings.

Booted under kernel 4.9, sudo lspci -vv for the radeon card shows:
        Capabilities: [50] Power Management version 3
                Flags: PMEClk- DSI- D1+ D2+ AuxCurrent=0mA
        PME(D0-,D1+,D2+,D3hot+,D3cold-)
                Status: D3 NoSoftRst- PME-Enable- DSel=0 DScale=0 PME-
Under kernel 4.4 and 4.7 with the lower power consumption, sudo lspci -vv shows
"Unknown header type 7f".

Booted under kernel 4.9, sudo dmesg | grep 01:00.0 shows:
    [    0.515468] pci 0000:01:00.0: [1002:6660] type 00 class 0x038000
    [    0.515480] pci 0000:01:00.0: reg 0x10: [mem 0xe0000000-0xefffffff 64bit
pref]
    [    0.515489] pci 0000:01:00.0: reg 0x18: [mem 0xf7c00000-0xf7c3ffff
64bit]
    [    0.515495] pci 0000:01:00.0: reg 0x20: [io  0xe000-0xe0ff]
    [    0.515506] pci 0000:01:00.0: reg 0x30: [mem 0xf7c40000-0xf7c5ffff pref]
    [    0.515545] pci 0000:01:00.0: supports D1 D2
    [    0.515545] pci 0000:01:00.0: PME# supported from D1 D2 D3hot
    [    0.515566] pci 0000:01:00.0: System wakeup disabled by ACPI
    [    2.950049] radeon 0000:01:00.0: VRAM: 2048M 0x0000000000000000 -
0x000000007FFFFFFF (2048M used)
    [    2.950051] radeon 0000:01:00.0: GTT: 2048M 0x0000000080000000 -
0x00000000FFFFFFFF
    [    2.952510] radeon 0000:01:00.0: firmware: direct-loading firmware
radeon/hainan_pfp.bin
    [    2.952800] radeon 0000:01:00.0: firmware: direct-loading firmware
radeon/hainan_me.bin
    [    2.953657] radeon 0000:01:00.0: firmware: direct-loading firmware
radeon/hainan_ce.bin
    [    2.954265] radeon 0000:01:00.0: firmware: direct-loading firmware
radeon/hainan_rlc.bin
    [    2.955119] radeon 0000:01:00.0: firmware: direct-loading firmware
radeon/hainan_mc.bin
    [    2.955430] radeon 0000:01:00.0: firmware: direct-loading firmware
radeon/hainan_smc.bin
    [    2.989489] radeon 0000:01:00.0: WB enabled
    [    2.989491] radeon 0000:01:00.0: fence driver on ring 0 use gpu addr
0x0000000080000c00 and cpu addr 0xffff9e4896928c00
    [    2.989493] radeon 0000:01:00.0: fence driver on ring 1 use gpu addr
0x0000000080000c04 and cpu addr 0xffff9e4896928c04
    [    2.989494] radeon 0000:01:00.0: fence driver on ring 2 use gpu addr
0x0000000080000c08 and cpu addr 0xffff9e4896928c08
    [    2.989495] radeon 0000:01:00.0: fence driver on ring 3 use gpu addr
0x0000000080000c0c and cpu addr 0xffff9e4896928c0c
    [    2.989496] radeon 0000:01:00.0: fence driver on ring 4 use gpu addr
0x0000000080000c10 and cpu addr 0xffff9e4896928c10
    [    2.989498] radeon 0000:01:00.0: radeon: MSI limited to 32-bit
    [    2.989561] radeon 0000:01:00.0: radeon: using MSI.
    [    3.229692] [drm] Initialized radeon 2.48.0 20080528 for 0000:01:00.0 on
minor 1

There is no mention of D3cold for the radeon card. Comparing lspci and dmesg
output, the pattern seems to be D3cold+ in the device capabilities results in
"PME# supported from D0 D3hot D3cold" in dmesg.

I need the longer battery life for travelling and can cope easily without the
radeon card being used. Is there a workaround, perhaps something in the
modprobe.d, to make the radeon driver revert to old behaviour ie behave as if
there was no d3cold support on the system?