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

[Andrew Jones]

On Thu, Jan 11, 2024 at 03:00:58PM +0530, Sunil V L wrote:
> Add required callbacks to support Low Power Idle (LPI) on ACPI based
> RISC-V platforms.
> 
> Signed-off-by: Sunil V L <sunilvl@xxxxxxxxxxxxxxxx>
> ---
>  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

GENMASK might look nicer and the type mask is 0xF000000000000000ULL,
where 0x1000000000000000ULL means that the type is an SBI identifier.
We need both defined

#define RISCV_FFH_LPI_TYPE_MASK              0xF000000000000000ULL
#define RISCV_FFH_LPI_TYPE_SBI               0x1000000000000000ULL

as I point out below.

> +
> +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");

The comment and these lines match what's done in sbi_cpuidle_init().
How about a static helper function to avoid duplication?

> +		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
                                        ^ an

> +		 */

Comment block needs opening wing (/*)

> +		if (!(lpi->address & RISCV_FFH_LPI_TYPE_MASK) ||

This should be (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);
> +}
> +
> +#endif
> -- 
> 2.34.1
>

Thanks,
drew