QCA6174 seemingly randomly fails to wake

[theros at openmailbox.org]

Hello,

I am having issues with the ath10k driver and the Qualcomm Atheros 
QCA6174 network adapter. Seemingly randomly, the wireless connection on 
my laptop stops working. dmesg outputs a long series of:

[11061.645929] ath10k_pci 0000:07:00.0: failed to wake target for 
write32 of 0x0000025c at 0x0003543c: -110

Rarely a reboot fixes this and I can use the network adapter again, but 
more often than not, after a reboot, there is no output related to 
ath10k in dmesg and the laptop is behaving as if the network adapter is 
not present. The adapter eventually starts working again - I have not 
noticed a specific pattern, sometimes it is after a few hours, sometimes 
I couldn't get it working for days.

I have tried thoroughly searching online but was unable to find anything 
that would be of help. I do admit I am a little out of my depth here, 
but I will happily provide any further information necessary in order to 
diagnose and fix this.

I am on Xubuntu 15.10, kernel 4.2.0-16-generic.

Thanks.