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c45992cc2b
Add D1's nonretentive suspend state to the devicetree so S-mode software knows about it and can use it. Latency and power measurements were taken on an Allwinner Nezha board: - Entry latency was measured from the beginning of sbi_ecall_handler() to before the call to wfi() in sun20i_d1_hart_suspend(). - Exit latency was measured from the beginning of sbi_init() to before the call to sbi_hart_switch_mode() in init_warmboot(). - There was a 17.5 mW benefit from non-retentive suspend compared to WFI, with a 170 mW cost during the 107 us entry/exit period. This provides a break-even point around 1040 us. Residency includes entry latency, so round this up to 1100 us. - The hardware power sequence latency (after the WFI) is assumed to be negligible, so set the wakeup latency to the exit latency. Reviewed-by: Anup Patel <anup@brainfault.org> Signed-off-by: Samuel Holland <samuel@sholland.org>