Re: [PATCH v2 -next 2/3] ACPI: RISC-V: Add LPI driver

[Andrew Jones]

On Mon, Jan 15, 2024 at 03:40:55PM +0530, Sunil V L wrote:
> Enable Low Power Idle (LPI) based cpuidle driver for RISC-V platforms.
> It depends on SBI HSM calls for idle state transitions.
> 
> Signed-off-by: Sunil V L <sunilvl@xxxxxxxxxxxxxxxx>
> ---
>  drivers/acpi/riscv/Makefile  |  3 +-
>  drivers/acpi/riscv/cpuidle.c | 81 ++++++++++++++++++++++++++++++++++++
>  2 files changed, 83 insertions(+), 1 deletion(-)
>  create mode 100644 drivers/acpi/riscv/cpuidle.c
> 
> diff --git a/drivers/acpi/riscv/Makefile b/drivers/acpi/riscv/Makefile
> index 8b3b126e0b94..7309d92dd477 100644
> --- a/drivers/acpi/riscv/Makefile
> +++ b/drivers/acpi/riscv/Makefile
> @@ -1,2 +1,3 @@
>  # SPDX-License-Identifier: GPL-2.0-only
> -obj-y 	+= rhct.o
> +obj-y					+= rhct.o
> +obj-$(CONFIG_ACPI_PROCESSOR_IDLE)	+= cpuidle.o
> diff --git a/drivers/acpi/riscv/cpuidle.c b/drivers/acpi/riscv/cpuidle.c
> new file mode 100644
> index 000000000000..052ec3942902
> --- /dev/null
> +++ b/drivers/acpi/riscv/cpuidle.c
> @@ -0,0 +1,81 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Copyright (C) 2024, Ventana Micro Systems Inc
> + *	Author: Sunil V L <sunilvl@xxxxxxxxxxxxxxxx>
> + *
> + */
> +
> +#include <linux/acpi.h>
> +#include <acpi/processor.h>
> +#include <linux/cpu_pm.h>
> +#include <linux/cpuidle.h>
> +#include <linux/suspend.h>
> +#include <asm/cpuidle.h>
> +#include <asm/sbi.h>
> +#include <asm/suspend.h>
> +
> +#define RISCV_FFH_LPI_TYPE_MASK	GENMASK_ULL(63, 60)
> +#define RISCV_FFH_LPI_RSVD_MASK	GENMASK_ULL(59, 32)
> +
> +#define RISCV_FFH_LPI_TYPE_SBI	BIT_ULL(60)
> +
> +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;
> +
> +	if (!is_sbi_hsm_supported())
> +		return -ENODEV;
> +
> +	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) != RISCV_FFH_LPI_TYPE_SBI) ||
> +		    (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);
> +}
> -- 
> 2.34.1
>

Reviewed-by: Andrew Jones <ajones@xxxxxxxxxxxxxxxx>