Re: [PATCH v6 4/5] arm64: add support for ACPI Low Power Idle(LPI)

[Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>]

Hi Sudeep,

On Tue, Jun 14, 2016 at 03:48:38PM +0100, Sudeep Holla wrote:
> This patch adds appropriate callbacks to support ACPI Low Power Idle
> (LPI) on ARM64.
> 
> Now that arm_enter_idle_state is exactly same in both generic ARM{32,64}
> CPUIdle driver and ARM64 backend for ACPI processor idle driver, we can
> unify it and move to cpuidle-arm.h header.
> 
> Cc: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
> Cc: Mark Rutland <mark.rutland@arm.com>
> Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
> Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>
> Cc: linux-arm-kernel@lists.infradead.org
> Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
> ---
>  arch/arm64/kernel/cpuidle.c   | 17 +++++++++++++
>  drivers/cpuidle/cpuidle-arm.c | 23 ++----------------
>  drivers/firmware/psci.c       | 56 +++++++++++++++++++++++++++++++++++++++++++
>  include/linux/cpuidle-arm.h   | 30 +++++++++++++++++++++++
>  4 files changed, 105 insertions(+), 21 deletions(-)
>  create mode 100644 include/linux/cpuidle-arm.h

This patch seems fine by me, it would be good if Daniel can have
a look too.

Some minor comments below.

[...]

> diff --git a/drivers/firmware/psci.c b/drivers/firmware/psci.c
> index 03e04582791c..c6caa863d156 100644
> --- a/drivers/firmware/psci.c
> +++ b/drivers/firmware/psci.c
> @@ -13,6 +13,7 @@
>  
>  #define pr_fmt(fmt) "psci: " fmt
>  
> +#include <linux/acpi.h>
>  #include <linux/arm-smccc.h>
>  #include <linux/cpuidle.h>
>  #include <linux/errno.h>
> @@ -310,11 +311,66 @@ static int psci_dt_cpu_init_idle(struct device_node *cpu_node, int cpu)
>  	return ret;
>  }
>  
> +#ifdef CONFIG_ACPI
> +#include <acpi/processor.h>
> +
> +static int __maybe_unused psci_acpi_cpu_init_idle(unsigned int cpu)
> +{
> +	int i, count;
> +	u32 *psci_states;
> +	struct acpi_processor *pr;
> +	struct acpi_lpi_state *lpi;
> +
> +	pr = per_cpu(processors, cpu);
> +	if (unlikely(!pr || !pr->flags.has_lpi))
> +		return -EINVAL;
> +
> +	/*
> +	 * If the PSCI cpu_suspend function hook has not been initialized
> +	 * idle states must not be enabled, so bail out
> +	 */
> +	if (!psci_ops.cpu_suspend)
> +		return -EOPNOTSUPP;
> +
> +	count = pr->power.count - 1;
> +	if (count <= 0)
> +		return -ENODEV;
> +
> +	psci_states = kcalloc(count, sizeof(*psci_states), GFP_KERNEL);
> +	if (!psci_states)
> +		return -ENOMEM;
> +
> +	for (i = 0; i < count; i++) {
> +		u32 state;
> +
> +		lpi = &pr->power.lpi_states[i + 1];
> +		state = lpi->address & 0xFFFFFFFF;
> +		if (!psci_power_state_is_valid(state)) {
> +			pr_warn("Invalid PSCI power state %#x\n", state);
> +			kfree(psci_states);
> +			return -EINVAL;
> +		}
> +		psci_states[i] = state;
> +	}
> +	/* Idle states parsed correctly, initialize per-cpu pointer */
> +	per_cpu(psci_power_state, cpu) = psci_states;
> +	return 0;

Most of the code in this function is FW independent, it would be nice
to factor it out and add the respective ACPI/DT helper functions to
retrieve idle states count and parameters, we can update it later
anyway it is fine by me to leave it as it is.

> +}
> +#else
> +static int __maybe_unused psci_acpi_cpu_init_idle(unsigned int cpu)
> +{
> +	return -EINVAL;
> +}
> +#endif
> +
>  int psci_cpu_init_idle(unsigned int cpu)
>  {
>  	struct device_node *cpu_node;
>  	int ret;
>  
> +	if (!acpi_disabled)
> +		return psci_acpi_cpu_init_idle(cpu);
> +
>  	cpu_node = of_get_cpu_node(cpu, NULL);
>  	if (!cpu_node)
>  		return -ENODEV;
> diff --git a/include/linux/cpuidle-arm.h b/include/linux/cpuidle-arm.h
> new file mode 100644
> index 000000000000..b99bcb3f43dd
> --- /dev/null
> +++ b/include/linux/cpuidle-arm.h

arm-cpuidle.h for consistency with other (ARM) include/linux files ?

> @@ -0,0 +1,30 @@
> +#include <linux/cpu_pm.h>
> +
> +#include <asm/cpuidle.h>
> +
> +/*
> + * arm_enter_idle_state - Programs CPU to enter the specified state
> + */
> +static int arm_generic_enter_idle_state(int idx)
> +{
> +	int ret;
> +
> +	if (!idx) {
> +		cpu_do_idle();
> +		return idx;
> +	}
> +
> +	ret = cpu_pm_enter();
> +	if (!ret) {
> +		/*
> +		 * Pass idle state index to cpu_suspend which in turn will
> +		 * call the CPU ops suspend protocol with idle index as a
> +		 * parameter.
> +		 */
> +		ret = arm_cpuidle_suspend(idx);
> +
> +		cpu_pm_exit();
> +	}
> +
> +	return ret ? -1 : idx;
> +}

Either you do this, or we have to add it somehow somewhere in
drivers/cpuidle to avoid duplicating it.

@Daniel: do you have an opinion on this please ?

Thanks,
Lorenzo