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

Anup Patel
2024-01-12T05:05:19Z

On Thu, Jan 11, 2024 at 3:01 PM Sunil V L <sunilvl@ventanamicro.com> wrote:
>
> Add required callbacks to support Low Power Idle (LPI) on ACPI based
> RISC-V platforms.
>
> Signed-off-by: Sunil V L <sunilvl@ventanamicro.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