[PATCH v2 2/2] platform: generic: allwinner: Advertise nonretentive suspend

[Anup Patel]

On Mon, Jan 23, 2023 at 12:02 PM Samuel Holland <samuel at sholland.org> wrote:
>
> 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 at brainfault.org>
> Signed-off-by: Samuel Holland <samuel at sholland.org>

Applied this patch to the riscv/opensbi repo.

Thanks,
Anup

> ---
>
> (no changes since v1)
>
>  platform/generic/allwinner/sun20i-d1.c | 20 ++++++++++++++++++++
>  1 file changed, 20 insertions(+)
>
> diff --git a/platform/generic/allwinner/sun20i-d1.c b/platform/generic/allwinner/sun20i-d1.c
> index e2b76a3..295c159 100644
> --- a/platform/generic/allwinner/sun20i-d1.c
> +++ b/platform/generic/allwinner/sun20i-d1.c
> @@ -12,6 +12,7 @@
>  #include <sbi/sbi_error.h>
>  #include <sbi/sbi_hsm.h>
>  #include <sbi/sbi_pmu.h>
> +#include <sbi_utils/fdt/fdt_fixup.h>
>  #include <sbi_utils/fdt/fdt_helper.h>
>  #include <sbi_utils/irqchip/fdt_irqchip_plic.h>
>
> @@ -202,6 +203,24 @@ static int sun20i_d1_final_init(bool cold_boot, const struct fdt_match *match)
>         return 0;
>  }
>
> +static const struct sbi_cpu_idle_state sun20i_d1_cpu_idle_states[] = {
> +       {
> +               .name                   = "cpu-nonretentive",
> +               .suspend_param          = SBI_HSM_SUSPEND_NON_RET_DEFAULT,
> +               .local_timer_stop       = true,
> +               .entry_latency_us       = 40,
> +               .exit_latency_us        = 67,
> +               .min_residency_us       = 1100,
> +               .wakeup_latency_us      = 67,
> +       },
> +       { }
> +};
> +
> +static int sun20i_d1_fdt_fixup(void *fdt, const struct fdt_match *match)
> +{
> +       return fdt_add_cpu_idle_states(fdt, sun20i_d1_cpu_idle_states);
> +}
> +
>  static void thead_c9xx_pmu_ctr_enable_irq(uint32_t ctr_idx)
>  {
>         unsigned long mip_val;
> @@ -265,5 +284,6 @@ static const struct fdt_match sun20i_d1_match[] = {
>  const struct platform_override sun20i_d1 = {
>         .match_table    = sun20i_d1_match,
>         .final_init     = sun20i_d1_final_init,
> +       .fdt_fixup      = sun20i_d1_fdt_fixup,
>         .extensions_init = sun20i_d1_extensions_init,
>  };
> --
> 2.37.4
>