linux-kernel - Re: [PATCH 6/6] PSCI: cpuidle: Refactor CPU suspend power

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Message-ID: <CAPDyKFrhggN_TDcB-Qdhe6booD1MzMJTe90D4DyRCKTq3cgU=g@mail.gmail.com>
Date:   Tue, 23 Jul 2019 13:47:08 +0200
From:   Ulf Hansson <ulf.hansson@...aro.org>
To:     Lorenzo Pieralisi <lorenzo.pieralisi@....com>
Cc:     Linux PM <linux-pm@...r.kernel.org>, Will Deacon <will@...nel.org>,
        Sudeep Holla <sudeep.holla@....com>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Mark Rutland <mark.rutland@....com>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        LKML <linux-kernel@...r.kernel.org>,
        LAKML <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH 6/6] PSCI: cpuidle: Refactor CPU suspend power_state
 parameter handling

On Mon, 22 Jul 2019 at 17:38, Lorenzo Pieralisi
<lorenzo.pieralisi@....com> wrote:
>
> Current PSCI code handles idle state entry through the
> psci_cpu_suspend_enter() API, that takes an idle state index as a
> parameter and convert the index into a previously initialized
> power_state parameter before calling the PSCI.CPU_SUSPEND() with it.
>
> This is unwieldly, since it forces the PSCI firmware layer to keep track
> of power_state parameter for every idle state so that the
> index->power_state conversion can be made in the PSCI firmware layer
> instead of the CPUidle driver implementations.
>
> Move the power_state handling out of drivers/firmware/psci
> into the respective ACPI/DT PSCI CPUidle backends and convert
> the psci_cpu_suspend_enter() API to get the power_state
> parameter as input, which makes it closer to its firmware
> interface PSCI.CPU_SUSPEND() API.
>
> A notable side effect is that the PSCI ACPI/DT CPUidle backends
> now can directly handle (and if needed update) power_state
> parameters before handing them over to the PSCI firmware
> interface to trigger PSCI.CPU_SUSPEND() calls.
>
> Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@....com>
> Cc: Will Deacon <will@...nel.org>
> Cc: Ulf Hansson <ulf.hansson@...aro.org>
> Cc: Sudeep Holla <sudeep.holla@....com>
> Cc: Daniel Lezcano <daniel.lezcano@...aro.org>
> Cc: Catalin Marinas <catalin.marinas@....com>
> Cc: Mark Rutland <mark.rutland@....com>
> Cc: "Rafael J. Wysocki" <rjw@...ysocki.net>
> ---
>  arch/arm64/kernel/cpuidle.c    |  47 +++++++++-
>  drivers/cpuidle/cpuidle-psci.c |  87 +++++++++++++++++-
>  drivers/firmware/psci/psci.c   | 158 ++-------------------------------
>  include/linux/cpuidle.h        |  17 +++-
>  include/linux/psci.h           |   4 +-
>  5 files changed, 153 insertions(+), 160 deletions(-)
>
> diff --git a/arch/arm64/kernel/cpuidle.c b/arch/arm64/kernel/cpuidle.c
> index 4bcd1bca0dfc..e4d6af2fdec7 100644
> --- a/arch/arm64/kernel/cpuidle.c
> +++ b/arch/arm64/kernel/cpuidle.c
> @@ -47,6 +47,44 @@ int arm_cpuidle_suspend(int index)
>
>  #define ARM64_LPI_IS_RETENTION_STATE(arch_flags) (!(arch_flags))
>
> +static int psci_acpi_cpu_init_idle(unsigned int cpu)
> +{
> +       int i, count;
> +       struct acpi_lpi_state *lpi;
> +       struct acpi_processor *pr = per_cpu(processors, cpu);
> +
> +       /*
> +        * If the PSCI cpu_suspend function hook has not been initialized
> +        * idle states must not be enabled, so bail out
> +        */
> +       if (!psci_ops.cpu_suspend)
> +               return -EOPNOTSUPP;
> +
> +       if (unlikely(!pr || !pr->flags.has_lpi))
> +               return -EINVAL;
> +
> +       count = pr->power.count - 1;
> +       if (count <= 0)
> +               return -ENODEV;
> +
> +       for (i = 0; i < count; i++) {
> +               u32 state;
> +
> +               lpi = &pr->power.lpi_states[i + 1];
> +               /*
> +                * Only bits[31:0] represent a PSCI power_state while
> +                * bits[63:32] must be 0x0 as per ARM ACPI FFH Specification
> +                */
> +               state = lpi->address;
> +               if (!psci_power_state_is_valid(state)) {
> +                       pr_warn("Invalid PSCI power state %#x\n", state);
> +                       return -EINVAL;
> +               }
> +       }
> +
> +       return 0;
> +}
> +
>  int acpi_processor_ffh_lpi_probe(unsigned int cpu)
>  {
>         return psci_acpi_cpu_init_idle(cpu);
> @@ -54,10 +92,13 @@ int acpi_processor_ffh_lpi_probe(unsigned int cpu)
>
>  int acpi_processor_ffh_lpi_enter(struct acpi_lpi_state *lpi)
>  {
> +       u32 state = lpi->address;
> +
>         if (ARM64_LPI_IS_RETENTION_STATE(lpi->arch_flags))
> -               return CPU_PM_CPU_IDLE_ENTER_RETENTION(psci_cpu_suspend_enter,
> -                                               lpi->index);
> +               return CPU_PM_CPU_IDLE_ENTER_RETENTION_PARAM(psci_cpu_suspend_enter,
> +                                               lpi->index, state);
>         else
> -               return CPU_PM_CPU_IDLE_ENTER(psci_cpu_suspend_enter, lpi->index);
> +               return CPU_PM_CPU_IDLE_ENTER_PARAM(psci_cpu_suspend_enter,
> +                                            lpi->index, state);
>  }

I am not sure where the acpi+psci cpuidle code really belongs. Perhaps
some code should be moved into separate acpi+psci cpuidle driver?

In any case and whatever makes sense, it can be done on top of the
current series.

[...]

Kind regards
Uffe