(In reply to Maik Freudenberg from comment #42)
> The hda devices on 3D controller are existing but not completely configured
> by vendors leading to errors like
> [ 4790.121207] pci 0000:07:00.1: [10de:0e0f] type 00 class 0x040300
> [ 4790.121253] pci 0000:07:00.1: reg 0x10: [mem 0x00000000-0x00003fff]
> [ 4790.121610] pci 0000:07:00.1: BAR 0: no space for [mem size 0x00004000]
> [ 4790.121613] pci 0000:07:00.1: BAR 0: failed to assign [mem size 0x00004000]
> [ 4790.121900] snd_hda_intel 0000:07:00.1: Disabling MSI
> [ 4790.122493] snd_hda_intel 0000:07:00.1: can't ioremap BAR 0: [??? 0x00000000 flags 0x0]
> [ 5661.858112] snd_hda_intel 0000:07:00.1: ioremap error

Is this a Thunderbolt-attached GPU? AFAICS these errors are not caused by
missing bits in the device configuration but rather improper resource
allocation by the kernel. This is common with Thunderbolt, but Mika Westerberg
has upstreamed a bunch of fixes for 4.15 and more are currently being
upstreamed:

https://lkml.org/lkml/2017/10/13/791
https://www.spinics.net/lists/linux-pci/msg69483.html

Have you tried this on a 4.15 kernel or was it an older version? If the latter,
try on 4.15 again and see if the situation has improved.

> Looking at the vgaswitcheroo patches, these look like a really fine way to
> handle pm on these hda devices.

Thanks, glad you like them.