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At reset, the Redistributors are considered to be powered down. To power up the Redistributors, software must use the GICR_PWRR register.
The GICR_PWRR register can control Redistributor power management either by operating through the core, or through the Redistributor.
If operating through the core, each core must program its GICR_PWRR.RDPD = 0 and GICR_PWRR.RDAG = 0 to ensure that the Redistributor powers up. Alternatively, a single core can power up the Redistributor for all cores that connect to the same Redistributor by writing GICR_PWRR.RDPD = 0 and GICR_PWRR.RDAG = 1.
You can use GICR_PWRR.RDG to identify which core shares a Redistributor.
The powerup and powerdown sequences are shown in the following pseudocode:
Power off (setting RDPD to 1): // Check group not transitioning. repeat until (GICR_PWRR.RDGPD == GICR_PWRR.RDGPO) // Write to power the CPU off. GICR_PWRR.RDPD = 1; Power on (setting RDPD to 0): repeat // Check group not transitioning. repeat until (GICR_PWRR.RDGPD == GICR_PWRR.RDGPO) // Write to power the CPU on. GICR_PWRR.RDPD = 0; // Check access, if RDPD == 0 then powered on. until (GICR_PWRR.RDPD == 0)