wd(4) not waking up on resume

[coypu%SDF.ORG@localhost]

Hi,

I'm interested in working suspend on my Dell Inspiron n4030.
I've been looking into the various problems.

Currently, one of the big problems is that my wd(4) disk (which has root
mounted on it, too) rarely wakes up on resume.

This device is:
wd0: <WDC WD3200BEVT-75ZCT2>
wd0: drive supports 16-sector PIO transfers, LBA48 addressing
wd0: 298 GB, 620181 cyl, 16 head, 63 sec, 512 bytes/sect x 625142448
sectors
wd0: drive supports PIO mode 4, DMA mode 2, Ultra-DMA mode 6 (Ultra/133)
wd0(ahcisata0:0:0): using PIO mode 4, DMA mode 2, Ultra-DMA mode 6
(Ultra/133) (using DMA)

This is running NetBSD-7.0_STABLE (201606022350Z)

At the age of 6200 power cycles (if SMART is to be believed), it is
possible that the disk itself is not in great shape. I had one with
similar conditions fail recently.

Running just:
# while true; do sleep 2 && date && drvctl -S wd0 && drvctl -R wd0 && echo 'asd' > $RANDOM; done

Showed that it fails (i.e., hangs at write, as the disk did not resume)
very quickly, but I have seen it succeed one suspend & resume before.

If I send an interrupt (like pressing power button for a bit), it will
wake up the disk and the activity continues, however this unfortunately
also shuts down my machine.

I've been trying to add debugging information by setting pmf_debug...=1
in sys/kern/kern_pmf.c, but I do not see any such messages :-( I am unsure
if I'm doing the right thing, or looking in the right place.

Any suggestions?

Thanks.


side note: sys/kern/kern_pmf.c:57-60 should probably be deleted. we do
not need to debug all the time.