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

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Message-ID: <ZaS9gQS4fURoiffV@sunil-laptop>
Date: Mon, 15 Jan 2024 10:37:13 +0530
From: Sunil V L <sunilvl@...tanamicro.com>
To: Anup Patel <anup@...infault.org>
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 Fri, Jan 12, 2024 at 10:35:07AM +0530, Anup Patel wrote:
> 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.
> 
Okay, sure. Let me send v2 with your suggestion.

Thanks,
Sunil