The below Table 30-6 lists the clock management settings applicable at PRU-ICSS subsystem level (first level of local power management).
Note: For more details on the slave idle protocol (slave
port) and master standby protocol (master port) between PRU-ICSS and device
PRCM, refer to the Section 3.1.1.1.3, Module-Level Clock Management in the Power, Reset and Clock
Management.
Table 30-6 PRU-ICSS Idle/Standby Support| IDLE/STANDBY Mode | Comments |
|---|
| NO IDLE | |
| SMART IDLE | Default State |
| Wake-up capable SMART IDLE | not supported |
| FORCE IDLE | |
| NO STANDBY | |
| SMART STANDBY | Default State |
| Wake-up capable SMART STANDBY | not supported |
| FORCE STANDBY | |
Note: Not all of the PRU-ICSS outputs meet the IDLE state. Only the power protocol and L3_MAIN signals are Idled with all functional and interface clocks being shut-down.
A transition from an ACTIVE/Normal state to an IDLE (L3_MAIN slave) + STANDBY (L3_MAIN masters) state is performed as per the sequence:
- The host (i.e. device MPU, DSP1, etc.) requests that the PRU firmware goes into IDLE state and waits for acknowledgement.
- The host issues Clock Stop Request in register
PRUSS_CGR to modules with gateable clocks defined at second power management
level (see Power, Reset and Clock Management)
- The host initiates MStandby via assertion to HIGH
of the bit: PRUSS_SYSCFG [4] STANDBY_INIT (PRU-ICSS clock management
configuration register).
- The host software gets the device PRCM to issue
an IDLE Request (SidleReq) towards the PRU-ICSS slave port. This is done via
writing to device PRCM clock management registers dedicated to PRU-ICSS:
CM_L4PER2_PRUSS1_CLKCTRL and CM_L4PER2_PRUSS2_CLKCTRL in PRCM Register
Manual of the Power Reset and Clock Management.
- The PRU-ICSS acknowledges IDLE Request and enters the IDLE+STANDBY state.
A transition from an IDLE + STANDBY state to an ACTIVE/ Normal state is performed as per the sequence:
- The host (i.e. device MPU, DSP1, etc.) software
gets the PRCM to de-assert IDLE Request - This is done via writing to device
PRCM clock management registers dedicated to PRU-ICSS:
CM_L4PER2_PRUSS1_CLKCTRLand CM_L4PER2_PRUSS2_CLKCTRL in PRCM Register
Manual of the Power Reset and Clock Management.
- The host CPU de-asserts the ClockStopReq to
modules with gateable clocks defined at second power management level, and
wait for the ClockStopAck to be asserted. This is done via PRU-ICSS host
writing/reading the PRUSS_CGR.
- The host CPU enables "NO STANDBY" via assertion
of the PRUSS_SYSCFG[3:2] STANDBY_MODE to 0x1.