Here is a syslog from krillin rc-proposed 230 when the problem is reproduced.
@20:18:20 the call is initiated from the BT device, the device wakes up and there is an ATD command to setup the call but immediately the device suspends again.

Jan 14 20:18:20 ubuntu-phablet kernel: [  187.068163][SPM] md_settle = 99, settle = 99
Jan 14 20:18:20 ubuntu-phablet kernel: [  187.068163][SPM] sec = 5400, wakesrc = 0x3204564 (1)(1)
Jan 14 20:18:20 ubuntu-phablet kernel: [  187.068163][SPM] wake up by CONN (0x80000c00)(0x400)(250871)
Jan 14 20:18:20 ubuntu-phablet kernel: [  187.068163][SPM] event_reg = 0x90010000, isr = 0x10, r13 = 0xea060842
Jan 14 20:18:20 ubuntu-phablet kernel: [  187.068163]wdt enable spm timer.....
Jan 14 20:18:20 ubuntu-phablet kernel: [  187.068163][WDT] resume(1)
Jan 14 20:18:20 ubuntu-phablet kernel: [  187.068169]Suspended for 0.000 seconds
Jan 14 20:18:20 ubuntu-phablet kernel: [  187.071005][MATV] resume
Jan 14 20:18:20 ubuntu-phablet kernel: [  187.071119]Mali<1>: Mali PM: mali_pm_resume
Jan 14 20:18:20 ubuntu-phablet kernel: [  187.071515][Serial_Core]: By pass Set termio
Jan 14 20:18:20 ubuntu-phablet kernel: [  187.071526][UART0] Resume(0)!
Jan 14 20:18:20 ubuntu-phablet kernel: [  187.071545][UART1] Resume(0)!
Jan 14 20:18:20 ubuntu-phablet kernel: [  187.071559]GPIO_UART_URXD3_PIN is not properly set p2
Jan 14 20:18:20 ubuntu-phablet kernel: [  187.071570][UART2] Resume(0)!
Jan 14 20:18:20 ubuntu-phablet kernel: [  187.071584]GPIO_UART_URXD4_PIN is not properly set p2
Jan 14 20:18:20 ubuntu-phablet kernel: [  187.071595][UART3] Resume(0)!
Jan 14 20:18:20 ubuntu-phablet kernel: [  187.258608]sd card rocr <0xc0ff8000>
Jan 14 20:18:20 ubuntu-phablet kernel: [  187.262823][Reset and init thermal controller]
Jan 14 20:18:20 ubuntu-phablet kernel: [  187.262852][PTP] PTP_INIT_02() start (ptp_level = 0x0).
Jan 14 20:18:20 ubuntu-phablet kernel: [  187.262860][PTP] DCVOFFSETIN = 0xffffff2a
Jan 14 20:18:20 ubuntu-phablet kernel: [  187.262867][PTP] AGEVOFFSETIN = 0x0
Jan 14 20:18:20 ubuntu-phablet kernel: [  187.262884][PTP] PTP_MON_MODE() start (ptp_level = 0x0).
Jan 14 20:18:20 ubuntu-phablet ofonod[1923]: Server: < ATD0629161837;\r
Jan 14 20:18:20 ubuntu-phablet kernel: [  187.263513]Restarting tasks ... done.
Jan 14 20:18:20 ubuntu-phablet kernel: [  187.268147][pm_notifier_call_chain]: there are 4 notify callbacks, event = 4
Jan 14 20:18:20 ubuntu-phablet kernel: [  187.268206]msdc: 0,mmc_schedule_delayed_work ret= 1
Jan 14 20:18:20 ubuntu-phablet kernel: [  187.268264]msdc: 1,mmc_schedule_delayed_work ret= 1
Jan 14 20:18:20 ubuntu-phablet kernel: [  187.268286]PM: suspend exit 2016-01-14 20:18:20.198010769 UTC
Jan 14 20:18:20 ubuntu-phablet kernel: [  187.268514]PM: suspend entry 2016-01-14 20:18:20.198236077 UTC
...


Then nothing happens until 20:20:12 (112s) and the device finally wakes up,  it makes the call and the display turns on.

Jan 14 20:20:12 ubuntu-phablet kernel: [  187.553595]Restarting tasks ... done.
Jan 14 20:20:12 ubuntu-phablet kernel: [  187.564436][pm_notifier_call_chain]: there are 4 notify callbacks, event = 4
Jan 14 20:20:12 ubuntu-phablet kernel: [  187.564493]msdc: 0,mmc_schedule_delayed_work ret= 1
Jan 14 20:20:12 ubuntu-phablet kernel: [  187.564555]msdc: 1,mmc_schedule_delayed_work ret= 1
Jan 14 20:20:12 ubuntu-phablet kernel: [  187.564579]PM: suspend exit 2016-01-14 20:20:12.208718461 UTC
Jan 14 20:20:12 ubuntu-phablet kernel: [  187.564624]active wakeup source: pmicAuxadc irq wakelock
Jan 14 20:20:12 ubuntu-phablet ofonod[1923]: Server: > \r\nOK\r\n\r\n+CIEV: 3,2\r\n
Jan 14 20:20:12 ubuntu-phablet powerd[947]: turn_display_on(1)
Jan 14 20:20:12 ubuntu-phablet powerd[947]: signalling activity via HAL

...