Commit 81d549e0 authored by Lorenzo Pieralisi's avatar Lorenzo Pieralisi Committed by Will Deacon
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ARM: psci: cpuidle: Introduce PSCI CPUidle driver 



PSCI firmware is the standard power management control for
all ARM64 based platforms and it is also deployed on some
ARM 32 bit platforms to date.

Idle state entry in PSCI is currently achieved by calling
arm_cpuidle_init() and arm_cpuidle_suspend() in a generic
idle driver, which in turn relies on ARM/ARM64 CPUidle back-end
to relay the call into PSCI firmware if PSCI is the boot method.

Given that PSCI is the standard idle entry method on ARM64 systems
(which means that no other CPUidle driver are expected on ARM64
platforms - so PSCI is already a generic idle driver), in order to
simplify idle entry and code maintenance, it makes sense to have a PSCI
specific idle driver so that idle code that it is currently living in
drivers/firmware directory can be hoisted out of it and moved
where it belongs, into a full-fledged PSCI driver, leaving PSCI code
in drivers/firmware as a pure firmware interface, as it should be.

Implement a PSCI CPUidle driver. By default it is a silent Kconfig entry
which is left unselected, since it selection would clash with the
generic ARM CPUidle driver that provides a PSCI based idle driver
through the arm/arm64 arches back-ends CPU operations.

Signed-off-by: default avatarLorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Acked-by: default avatarDaniel Lezcano <daniel.lezcano@linaro.org>
Reviewed-by: default avatarUlf Hansson <ulf.hansson@linaro.org>
Reviewed-by: default avatarSudeep Holla <sudeep.holla@arm.com>
Cc: Ulf Hansson <ulf.hansson@linaro.org>
Cc: Sudeep Holla <sudeep.holla@arm.com>
Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Signed-off-by: default avatarWill Deacon <will@kernel.org>
parent e76d8b70

MAINTAINERS

+8 −0
Original line number Diff line number Diff line
@@ -4290,6 +4290,14 @@ S: Supported 
F:	drivers/cpuidle/cpuidle-exynos.c

F:	arch/arm/mach-exynos/pm.c



CPUIDLE DRIVER - ARM PSCI

M:	Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>

M:	Sudeep Holla <sudeep.holla@arm.com>

L:	linux-pm@vger.kernel.org

L:	linux-arm-kernel@lists.infradead.org

S:	Supported

F:	drivers/cpuidle/cpuidle-psci.c



CPU IDLE TIME MANAGEMENT FRAMEWORK

M:	"Rafael J. Wysocki" <rjw@rjwysocki.net>

M:	Daniel Lezcano <daniel.lezcano@linaro.org>

drivers/cpuidle/Kconfig.arm

+10 −0
Original line number Diff line number Diff line
@@ -13,6 +13,16 @@ config ARM_CPUIDLE 
          initialized by calling the CPU operations init idle hook

          provided by architecture code.



config ARM_PSCI_CPUIDLE

	bool

	depends on ARM_PSCI_FW

	select DT_IDLE_STATES

	select CPU_IDLE_MULTIPLE_DRIVERS

	help

	  Select this to enable PSCI firmware based CPUidle driver for ARM.

	  It provides an idle driver that is capable of detecting and

	  managing idle states through the PSCI firmware interface.



config ARM_BIG_LITTLE_CPUIDLE

	bool "Support for ARM big.LITTLE processors"

	depends on ARCH_VEXPRESS_TC2_PM || ARCH_EXYNOS

drivers/cpuidle/Makefile

+1 −0
Original line number Diff line number Diff line
@@ -20,6 +20,7 @@ obj-$(CONFIG_ARM_U8500_CPUIDLE) += cpuidle-ux500.o 
obj-$(CONFIG_ARM_AT91_CPUIDLE)          += cpuidle-at91.o

obj-$(CONFIG_ARM_EXYNOS_CPUIDLE)        += cpuidle-exynos.o

obj-$(CONFIG_ARM_CPUIDLE)		+= cpuidle-arm.o

obj-$(CONFIG_ARM_PSCI_CPUIDLE)		+= cpuidle-psci.o



###############################################################################

# MIPS drivers

drivers/cpuidle/cpuidle-psci.c

0 → 100644
+151 −0
Original line number Diff line number Diff line 
// SPDX-License-Identifier: GPL-2.0-only

/*

 * PSCI CPU idle driver.

 *

 * Copyright (C) 2019 ARM Ltd.

 * Author: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>

 */



#define pr_fmt(fmt) "CPUidle PSCI: " fmt



#include <linux/cpuidle.h>

#include <linux/cpumask.h>

#include <linux/cpu_pm.h>

#include <linux/kernel.h>

#include <linux/module.h>

#include <linux/of.h>

#include <linux/of_device.h>

#include <linux/psci.h>

#include <linux/slab.h>



#include <asm/cpuidle.h>



#include "dt_idle_states.h"



static int psci_enter_idle_state(struct cpuidle_device *dev,

				struct cpuidle_driver *drv, int idx)

{

	return CPU_PM_CPU_IDLE_ENTER(psci_cpu_suspend_enter, idx);

}



static struct cpuidle_driver psci_idle_driver __initdata = {

	.name = "psci_idle",

	.owner = THIS_MODULE,

	/*

	 * PSCI idle states relies on architectural WFI to

	 * be represented as state index 0.

	 */

	.states[0] = {

		.enter                  = psci_enter_idle_state,

		.exit_latency           = 1,

		.target_residency       = 1,

		.power_usage		= UINT_MAX,

		.name                   = "WFI",

		.desc                   = "ARM WFI",

	}

};



static const struct of_device_id psci_idle_state_match[] __initconst = {

	{ .compatible = "arm,idle-state",

	  .data = psci_enter_idle_state },

	{ },

};



static int __init psci_idle_init_cpu(int cpu)

{

	struct cpuidle_driver *drv;

	struct device_node *cpu_node;

	const char *enable_method;

	int ret = 0;



	cpu_node = of_cpu_device_node_get(cpu);

	if (!cpu_node)

		return -ENODEV;



	/*

	 * Check whether the enable-method for the cpu is PSCI, fail

	 * if it is not.

	 */

	enable_method = of_get_property(cpu_node, "enable-method", NULL);

	if (!enable_method || (strcmp(enable_method, "psci")))

		ret = -ENODEV;



	of_node_put(cpu_node);

	if (ret)

		return ret;



	drv = kmemdup(&psci_idle_driver, sizeof(*drv), GFP_KERNEL);

	if (!drv)

		return -ENOMEM;



	drv->cpumask = (struct cpumask *)cpumask_of(cpu);



	/*

	 * Initialize idle states data, starting at index 1, since

	 * by default idle state 0 is the quiescent state reached

	 * by the cpu by executing the wfi instruction.

	 *

	 * If no DT idle states are detected (ret == 0) let the driver

	 * initialization fail accordingly since there is no reason to

	 * initialize the idle driver if only wfi is supported, the

	 * default archictectural back-end already executes wfi

	 * on idle entry.

	 */

	ret = dt_init_idle_driver(drv, psci_idle_state_match, 1);

	if (ret <= 0) {

		ret = ret ? : -ENODEV;

		goto out_kfree_drv;

	}



	/*

	 * Initialize PSCI idle states.

	 */

	ret = psci_cpu_init_idle(cpu);

	if (ret) {

		pr_err("CPU %d failed to PSCI idle\n", cpu);

		goto out_kfree_drv;

	}



	ret = cpuidle_register(drv, NULL);

	if (ret)

		goto out_kfree_drv;



	return 0;



out_kfree_drv:

	kfree(drv);

	return ret;

}



/*

 * psci_idle_init - Initializes PSCI cpuidle driver

 *

 * Initializes PSCI cpuidle driver for all CPUs, if any CPU fails

 * to register cpuidle driver then rollback to cancel all CPUs

 * registration.

 */

static int __init psci_idle_init(void)

{

	int cpu, ret;

	struct cpuidle_driver *drv;

	struct cpuidle_device *dev;



	for_each_possible_cpu(cpu) {

		ret = psci_idle_init_cpu(cpu);

		if (ret)

			goto out_fail;

	}



	return 0;



out_fail:

	while (--cpu >= 0) {

		dev = per_cpu(cpuidle_devices, cpu);

		drv = cpuidle_get_cpu_driver(dev);

		cpuidle_unregister(drv);

		kfree(drv);

	}



	return ret;

}

device_initcall(psci_idle_init);

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