How to reset Cisco FXS voice card and port

Cisco FXS voice card is very handy solution if you already have Cisco router and DSP module on the router. It makes your router has a VoIP capability and easy to setup by enable voice gateway feature on the fly. It is not necessarily saying LSC level, but it does real VoIP on your system. In my experience, it is very robust and not much trouble.
Well, nothing is perfect, right? Recently, we had a chance to troubleshoot VoIP link down issue and it turned out Cisco FXS Voice card related.

Somehow all the FXS ports were frozen and status was showing as down/down. The Cisco router model was 2921 with 15.2.(3)T4.
Bounced each voice port, but it didn’t do anything. Of course we could not power cycle the router middle of day.

Here is what I have done and worked

Reset the DSP process.

test dsp device [SLOT ID] [DSP ID, all] reset   command

FXS-Router# test dsp device 0 all reset ; 

To reset individual port, try below

FXS-Router(config)# voice-port 0/0/1
FXS-Router(config-voiceport)# shut
FXS-Router(config-voiceport)# no shut

I hope it is informative for you.