SPRUIE9D May 2017 – May 2024 DRA74P , DRA75P , DRA76P , DRA77P
The PRCM module can require the GPIO modules to be idled for power-saving purposes.
The general-purpose interface has eight identical idle mode request/acknowledge (handshake) mechanisms with the PRCM module (see Section 29.4.6.2, Wake-Up Requests Generation): one per GPIO module. The general-purpose interface allows the GPIO modules to enter idle mode based on the GPIOi.GPIO_SYSCONFIG[4:3] IDLEMODE bit field.
Idle acknowledge depends on the configuration and activity of each GPIO module:
When the GPIO module is configured in smart-idle mode, it checks for more activity (capture of the input GPIO pins in the GPIOi.GPIO_DATAIN register is complete with no pending interrupt; all interrupt status bits are cleared), and there is no write access to the GPIO.GPIO_DEBOUNCINGTIME register, which is waiting to be synchronized.
Idle acknowledge is then asserted and the module enters into idle mode. It waits for active system clock gating by the PRCM module (when all peripherals supplied by the same L4 interface clock domain are also ready for idle).
In idle mode (that is, when the PRCM module gates the interface clock), no interrupt occurs.
If the GPIOi.GPIO_SYSCONFIG[4:3] IDLEMODE bit field selects smart-idle or smart-idle wake-up mode, the GPIO module evaluates its internal capability to have the interface clock switched off. Once all internal activity ceases (the DATA INPUT REGISTER completed to capture the input GPIO pins, there is no pending interrupt, all interrupt status bits are cleared, and there is no write access to the GPIO_DEBOUNCINGTIME register pending to be synchronized), the idle acknowledge is asserted and the GPIO enters into Idle mode, ready to issue a wake-up request when the expected transition occurs on an enabled GPIO input pin. This wake-up request is effectively sent only if the GPIOi.GPIO_SYSCONFIG[2] ENAWAKEUP bit of the system configuration register enables the GPIO wake-up capability (see GPIO_SYSCONFIG). When the system is awake, the IDLE request goes inactive, the idle acknowledge and wake-up request (if the GPIO triggered the wake-up in the system) signals are immediately deasserted, and the asynchronous wake-up request (if it exists) is reflected into the synchronous interrupt status registers.
When the GPIO module is configured in force-idle mode (the GPIOi.GPIO_SYSCONFIG[4:3] IDLEMODE bit field = 0x0) and receives an IDLE request from the PRCM module, the GPIO module waits unconditionally for active system clock gating by the PRCM module. (This occurs only when all peripherals supplied by the same L4 interface clock domain are also ready for idle.)
When in idle mode (that is, when the PRCM module gates the interface clock), the module (in inactive mode) has no activity, the interface clock paths are gated, an interrupt cannot be generated, and the wake-up feature is totally inhibited.
When the GPIO module is configured in no-idle mode (the GPIOi.GPIO_SYSCONFIG[4:3] IDLEMODE bit field = 0x1) and receives an IDLE request from the PRCM module, the GPIO module does not go into idle mode and the idle acknowledge is never sent.
For more information about the idle modes, see Power Management, in Power, Reset, and Clock Management.