linux-kernel - Re: [PATCH -next 2/2] cpuidle: RISC-V: Add ACPI LPI support

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Message-ID: <CAAhSdy22JrFOS8V-FC=ZCQiybhcJCszxy_TsnGAzuzYA06Mw7Q@mail.gmail.com>
Date: Fri, 12 Jan 2024 10:35:07 +0530
From: Anup Patel <anup@...infault.org>
To: Sunil V L <sunilvl@...tanamicro.com>
Cc: linux-acpi@...r.kernel.org, linux-kernel@...r.kernel.org, 
	linux-pm@...r.kernel.org, linux-riscv@...ts.infradead.org, 
	"Rafael J . Wysocki" <rafael@...nel.org>, Len Brown <lenb@...nel.org>, 
	Daniel Lezcano <daniel.lezcano@...aro.org>, Paul Walmsley <paul.walmsley@...ive.com>, 
	Palmer Dabbelt <palmer@...belt.com>, Albert Ou <aou@...s.berkeley.edu>, 
	Conor Dooley <conor@...nel.org>, Andrew Jones <ajones@...tanamicro.com>, 
	Atish Kumar Patra <atishp@...osinc.com>
Subject: Re: [PATCH -next 2/2] cpuidle: RISC-V: Add ACPI LPI support

On Thu, Jan 11, 2024 at 3:01 PM Sunil V L <sunilvl@...tanamicro.com> wrote:
>
> Add required callbacks to support Low Power Idle (LPI) on ACPI based
> RISC-V platforms.
>
> Signed-off-by: Sunil V L <sunilvl@...tanamicro.com>
> ---
>  drivers/cpuidle/cpuidle-riscv-sbi.c | 78 +++++++++++++++++++++++++++++
>  1 file changed, 78 insertions(+)
>
> diff --git a/drivers/cpuidle/cpuidle-riscv-sbi.c b/drivers/cpuidle/cpuidle-riscv-sbi.c
> index e8094fc92491..cea67a54ab39 100644
> --- a/drivers/cpuidle/cpuidle-riscv-sbi.c
> +++ b/drivers/cpuidle/cpuidle-riscv-sbi.c
> @@ -632,3 +632,81 @@ static int __init sbi_cpuidle_init(void)
>         return 0;
>  }
>  device_initcall(sbi_cpuidle_init);
> +
> +#ifdef CONFIG_ACPI_PROCESSOR_IDLE
> +
> +#include <linux/acpi.h>
> +#include <acpi/processor.h>
> +
> +#define RISCV_FFH_LPI_TYPE_MASK                0x1000000000000000ULL
> +#define RISCV_FFH_LPI_RSVD_MASK                0x0FFFFFFF00000000ULL
> +
> +static int acpi_cpu_init_idle(unsigned int cpu)
> +{
> +       int i;
> +       struct acpi_lpi_state *lpi;
> +       struct acpi_processor *pr = per_cpu(processors, cpu);
> +
> +       if (unlikely(!pr || !pr->flags.has_lpi))
> +               return -EINVAL;
> +
> +       /*
> +        * The SBI HSM suspend function is only available when:
> +        * 1) SBI version is 0.3 or higher
> +        * 2) SBI HSM extension is available
> +        */
> +       if (sbi_spec_version < sbi_mk_version(0, 3) ||
> +           !sbi_probe_extension(SBI_EXT_HSM)) {
> +               pr_warn("HSM suspend not available\n");
> +               return -EINVAL;
> +       }
> +
> +       if (pr->power.count <= 1)
> +               return -ENODEV;
> +
> +       for (i = 1; i < pr->power.count; i++) {
> +               u32 state;
> +
> +               lpi = &pr->power.lpi_states[i];
> +
> +               /* Validate Entry Method as per FFH spec.
> +                * bits[63:60] should be 0x1
> +                * bits[59:32] should be 0x0
> +                * bits[31:0] represent a SBI power_state
> +                */
> +               if (!(lpi->address & RISCV_FFH_LPI_TYPE_MASK) ||
> +                   (lpi->address & RISCV_FFH_LPI_RSVD_MASK)) {
> +                       pr_warn("Invalid LPI entry method %#llx\n", lpi->address);
> +                       return -EINVAL;
> +               }
> +
> +               state = lpi->address;
> +               if (!sbi_suspend_state_is_valid(state)) {
> +                       pr_warn("Invalid SBI power state %#x\n", state);
> +                       return -EINVAL;
> +               }
> +       }
> +
> +       return 0;
> +}
> +
> +int acpi_processor_ffh_lpi_probe(unsigned int cpu)
> +{
> +       return acpi_cpu_init_idle(cpu);
> +}
> +
> +int acpi_processor_ffh_lpi_enter(struct acpi_lpi_state *lpi)
> +{
> +       u32 state = lpi->address;
> +
> +       if (state & SBI_HSM_SUSP_NON_RET_BIT)
> +               return CPU_PM_CPU_IDLE_ENTER_PARAM(sbi_suspend,
> +                                                  lpi->index,
> +                                                  state);
> +       else
> +               return CPU_PM_CPU_IDLE_ENTER_RETENTION_PARAM(sbi_suspend,
> +                                                            lpi->index,
> +                                                            state);
> +}
> +
> +#endif

Lets keep the cpuidle-riscv-sbi.c driver focused on DT only. Instead,
I would suggest moving the required function from cpuidle-riscv-sbi.c
to arch/riscv and have a separate driver under driver/acpi/riscv for
LPI states.

Regards,
Anup