Air carrier Captain reported an FMC failure in cruise prior to oceanic entry point resulted in return to departure airport.

Narrative

Preflight; departure; initial cruise all nominal. Oceanic clearance received. Approx 30 min from reaching oceanic entry point ZZZZZ; the FO (First Officer) FMC display locked into the MENU (SAT) display. No instrumentation; EICAS or status message for an R FMC failure displayed. Contacted Dispatch via SAT phone; requested patch to Maintenance Control. Explained situation; all attempts at selection useless. Unable to access FMS inputs from the R FMS display. Requested permission to pull and reset CB (Circuit Breaker) to reset FMS Display; maintenance control stated that no history of previous write-up. Maintenance control provided the exact CB location for R FMC display but stated that they could not authorize a CB recycle but that I was free to use my Captain's discretion. I requested to check with the maintenance control supervisor if they would approve a CB recycle. While on hold; I looked through the maintenance log - Discovered exact same situation written up X days previously with corrective action of 'reset procedures followed; ops check good' When Maintenance Control came back on the line; I provided logbook page number with previous write-up. Maintenance control stated 'I wonder why it didn't show up in my search?' We reviewed the MEL for operation with a single FMC and ETOPS prohibited with operation limited to the USA contiguous 48 states. Maintenance control and dispatch said 'that technically; we could enter ETOPS airspace since we had 2 operating FMC's.' I stated to both Maintenance Control and Dispatch that we were effectively a single FMC operation as we had no control or ability to input anything via the R FMC display and used the analogy of having a working TV (FMS) but with no remote or buttons to change the channel; volume or power on or off; and I am operating on the premise that we are now in a single FMC condition. I also further emphasized that if the L FMC Display also locked up or failed; we would have ZERO ability to uplink; enter or review ANY route; winds; performance; holding; progress; position or navigation information. Because we had not yet entered oceanic airspace; I made the decision; after consulting with the other 2 pilots and with dispatch concurrence; that we would return to ZZZZ. I also clearly stated that we would NOT be [requesting priority handling] since all systems were nominal (with the exception of the R FMC display) and that while we were now at approx 505.0K lbs GWT and 45.0K lbs above our maximum landing weight of 460.0K lbs; I elected to not jettison fuel but to fly towards ZZZZ and while at a lower altitude in the terminal area; request holding to burn down to our our max landing weight of 460.0K lbs before exiting the hold to proceed towards landing. This was accomplished in cooperation with ATC. The flight attendants and passengers were fully informed of the return to ZZZZ and the basic reason why. Because of the time required to return back to the ZZZZ terminal area; I directed the flight attendants to continue with the passenger meal service that they had already started as it would be completed long before we began our descent into the terminal area to hold. Again; we did not [request priority handling] nor did we jettison fuel. After reaching our maximum landing weight of 460.0K lbs in the hold; we informed ATC that we could now proceed inbound to ZZZZ for landing. We were informed by ZZZZ operations that we would be parking at a hardstand and that the passengers were to remain onboard as ZZZZ MX (Maintenance) crews would be waiting to immediately board the aircraft and assess the situation. The approach; landing and taxiing to parking were all normal. After approx 20 min at the hardstand; with the passengers still aboard (including wheelchair passengers) we were informed that the flight had been 'delayed' until the following day. After all the passengers had been deplaned; we had crew lodging secured for the night and proceeded to the hotel. Upon returning to the same aircraft the next day; we noted in the maintenance log that the R FMC had been replaced; along with clearing out a previous MEL (blower unit). Of particular interest; we did note that in the maintenance log; it was stated by mx that the CDU (control display panel) operating software was out of date and was updated by ZZZZ mx.Having served previously as a MX Test pilot and other various roles on the Airbus 320; I feel it would be extremely beneficial if there was an authorized way to recycle a CB inflight as conditions warrant; with the concurrence of Maintenance Control (upon arrival in ZZZZ; the MX crews recycled the CB and the FMC unlocked and resumed normal operation).Also; I felt that there was an undertone not only to reset the CB at my own risk (which I refuse to do without Maintenance Control direction) but to continue on and enter into ETOPS airspace because it was 'technically' allowed to do so; even to the point that I was informed that Dispatch had contacted both ZZZZ and ZZZZ1 Oceanic control and that 'they had no problem with me continuing.'The company Threat and Error Management (TEM) that we are supposed to be guided by (and that I have personally taught to literally hundred of line pilots for over 15 years); clearly and unequivocally states and emphasized point of actively assess if what you are doing; or considering doing; is sensible.Continuing on; entering into ZZZZ1 Airspace and crossing the ocean with; for all practical purposes; only 1 fully functional FMC is both not sensible but increases the risk factor significantly. I personally have noted while in initial B-777 flight training; the lack of any reference; let alone emphasis; on the TEM at any level. In my opinion; Flight Training needs to correct this mindset and increase the emphasis and practicality of the TEM across the entire training platform and across all fleet types.