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

[Sunil V L]

On Thu, Jan 11, 2024 at 11:19:49AM +0100, Andrew Jones wrote:
> 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 at 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
> 
> 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
> 
Sure. Let me use GENMASK and define both MASK and SBI type.

> 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?
> 
Sure.

> > +		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 (/*)
> 
Okay.

> > +		if (!(lpi->address & RISCV_FFH_LPI_TYPE_MASK) ||
> 
> This should be (lpi->address & RISCV_FFH_LPI_TYPE_MASK) != RISCV_FFH_LPI_TYPE_SBI
> 
Sure.

Let me send v2 in couple of days with these changes.

Thanks!
Sunil

> > +		    (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