osmo-bts-trx: fix trx_init(): do not send OPSTART ACK blindly

It was reported that both osmo-bsc and osmo-bts-trx may end up
running in a half-broken state, when everything looks good and
the UEs can see the network, but all channel requests get
rejected due to "trx not usable" error:

  lchan_select.c:173 (bts=0) lchan_select_by_type(SDCCH)
  lchan_select.c:48 looking for lchan CCCH+SDCCH4: (bts=0,trx=0) trx not usable
  lchan_select.c:48 looking for lchan SDCCH8: (bts=0,trx=0) trx not usable
  lchan_select.c:239 (bts=0) Failed to select SDCCH channel

  lchan_select.c:173 (bts=0) lchan_select_by_type(TCH_H)
  lchan_select.c:48 looking for lchan TCH/H: (bts=0,trx=0) trx not usable
  lchan_select.c:239 (bts=0) Failed to select TCH_H channel

  lchan_select.c:173 (bts=0) lchan_select_by_type(TCH_F)
  lchan_select.c:48 looking for lchan TCH/F: (bts=0,trx=0) trx not usable
  lchan_select.c:239 (bts=0) Failed to select TCH_F channel

As was then figured out, this happens because the Radio Carrier
MO (Managed Object) remains Disabled even after the BSC has
sent OPSTART and the BTS ACKed it:

  oml.c:986 OC=RADIO-CARRIER(02) INST=(00,00,ff): Rx OPSTART
  l1_if.c:614 Rx OPSTART for RADIO-CARRIER MO
  l1_if.c:201 TRX_PROV(phy0-0)[0x1238c0]{OPEN_POWERON}:
              Event TRX_PROV_EV_CFG_ENABLE not permitted
  oml.c:144 OC=RADIO-CARRIER(02) INST=(00,00,ff): Tx Opstart Ack

It remains a mistery why the TRX_PROV FSM is already in state
OPEN_POWERON, while it's expected to be in state OPEN_POWEROFF,
but we definitely should not ACKnowledge the OPSTART if this
happens.  Send a NACK instead with cause NM_NACK_CANT_PERFORM.

Change-Id: I8727460acbf850b84df67a9cbdc25b47dee1fadd
Related: SYS#5063

0 files changed, 0 insertions, 0 deletions