drm-devel-kmod: no sound after monitor standby

Hi,

Using drm-devel-kmod-4.16.g20181027_1 with Intel Iris Plus Graphics 650
connected to monitor via HDMI.  Once monitor is back from standby,
there's no sound, however pindump seems to report everything is ok
(connected):

hdaa1: Dumping AFG pins:
hdaa1: nid   0x    as seq device       conn  jack    loc        color   misc
hdaa1:  3 18560010 1  0  Digital-out   Jack  Digital 0x18       Unknown 0
hdaa1:     Caps:    OUT              Sense: 0xc0000000 (connected, ELD
valid)
hdaa1: NumGPIO=0 NumGPO=0 NumGPI=0 GPIWake=0 GPIUnsol=0

I have found an easy workaround for this using `devctl suspend hdacc1;
devctl resume hdacc1`, but also wondering what would be correct way of
solving this?  Are the missing functions reported in dmesg somehow
related, especially the suspend/resume ones (pasted below)?

__pm_runtime_resume not implemented -- see your local kernel hacker
__pm_runtime_suspend not implemented -- see your local kernel hacker
pm_runtime_set_autosuspend_delay not implemented -- see your local
kernel hacker
__pm_runtime_use_autosuspend not implemented -- see your local kernel hacker

TIA for any hints/pointers.

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