SPRUIE9D May 2017 – May 2024 DRA74P , DRA75P , DRA76P , DRA77P
When the link of a RC enters L3 mode, the PIPE interface must go to P2 mode for power saving. The PCIe controller maintains the PIPE interface in P1 mode (PIPE clock running) and the internal registers accessible until the system requests entry into "Idle", and only then transition to P2: it is the device PRCM responsibility to Idle the module (PCIECTRL_TI_CONF_SYSCONFIG [3:2] IDLEMODE set to 0x2 - Smart Idle mode should be selected), in order to reach a low-power state. Transitioning to "P2", stops the PIPE clock and makes the register inaccessible, which in turn corresponds to an "IDLED" and disconnected from L3_MAIN PCIe slave port.
The "L3" state can only be exited when the RC re-enabling the Vmain power supply, and reconfiguring all PCIe registers from scratch: In both EP and RC cases, the system should detect Vmain power assertion, apply a fundamental reset, then bring the module out of "IDLE" and restart the link normally. All registers are reset.