[4/6] ARM: psci: cpuidle: Introduce PSCI CPUidle driver

Commit Message

Lorenzo Pieralisi July 22, 2019, 3:37 p.m. UTC

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: Lorenzo Pieralisi <[e-mail]>
Cc: Ulf Hansson <[e-mail]>
Cc: Sudeep Holla <[e-mail]>
Cc: Daniel Lezcano <[e-mail]>
Cc: Mark Rutland <[e-mail]>
Cc: "Rafael J. Wysocki" <[e-mail]>
---
 MAINTAINERS                    |   8 ++
 drivers/cpuidle/Kconfig.arm    |   3 +
 drivers/cpuidle/Makefile       |   1 +
 drivers/cpuidle/cpuidle-psci.c | 150 +++++++++++++++++++++++++++++++++
 4 files changed, 162 insertions(+)
 create mode 100644 drivers/cpuidle/cpuidle-psci.c

Comments

Ulf Hansson July 23, 2019, 11:46 a.m. UTC | #1

[...]

> +++ b/drivers/cpuidle/cpuidle-psci.c
> @@ -0,0 +1,150 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * PSCI CPU idle driver.
> + *
> + * Copyright (C) 2019 ARM Ltd.
> + * Author: Lorenzo Pieralisi <[e-mail]>
> + */
> +
> +#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/psci.h>
> +#include <linux/slab.h>
> +
> +#include <asm/cpuidle.h>

This should go away, right?

> +
> +#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;
> +
> +       drv = kmemdup(&psci_idle_driver, sizeof(*drv), GFP_KERNEL);
> +       if (!drv)
> +               return -ENOMEM;
> +
> +       drv->cpumask = (struct cpumask *)cpumask_of(cpu);
> +
> +       cpu_node = of_get_cpu_node(cpu, NULL);
> +       if (!cpu_node)
> +               return -ENODEV;

You should free drv in case of error here (goto out_kfree_drv; etc).

> +
> +       /*
> +        * 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;

You should free drv in case of error here (goto out_kfree_drv;).

> +
> +       /*
> +        * 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;
> +}
> +

[...]

Kind regards
Uffe

Lorenzo Pieralisi July 23, 2019, 2:15 p.m. UTC | #2

On Tue, Jul 23, 2019 at 01:46:56PM +0200, Ulf Hansson wrote:
> [...]
> 
> > +++ b/drivers/cpuidle/cpuidle-psci.c
> > @@ -0,0 +1,150 @@
> > +// SPDX-License-Identifier: GPL-2.0-only
> > +/*
> > + * PSCI CPU idle driver.
> > + *
> > + * Copyright (C) 2019 ARM Ltd.
> > + * Author: Lorenzo Pieralisi <[e-mail]>
> > + */
> > +
> > +#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/psci.h>
> > +#include <linux/slab.h>
> > +
> > +#include <asm/cpuidle.h>
> 
> This should go away, right?

We need to pull in cpu_do_idle() so it will have to stay there.

> > +#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;
> > +
> > +       drv = kmemdup(&psci_idle_driver, sizeof(*drv), GFP_KERNEL);
> > +       if (!drv)
> > +               return -ENOMEM;
> > +
> > +       drv->cpumask = (struct cpumask *)cpumask_of(cpu);
> > +
> > +       cpu_node = of_get_cpu_node(cpu, NULL);
> > +       if (!cpu_node)
> > +               return -ENODEV;
> 
> You should free drv in case of error here (goto out_kfree_drv; etc).
> 
> > +
> > +       /*
> > +        * 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;
> 
> You should free drv in case of error here (goto out_kfree_drv;).

True on both cases, I missed that, thanks.

Lorenzo

> > +
> > +       /*
> > +        * 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;
> > +}
> > +
> 
> [...]
> 
> Kind regards
> Uffe

Sudeep Holla Aug. 6, 2019, 4:10 p.m. UTC | #3

On Mon, Jul 22, 2019 at 04:37:43PM +0100, Lorenzo Pieralisi wrote:
> 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: Lorenzo Pieralisi <[e-mail]>
> Cc: Ulf Hansson <[e-mail]>
> Cc: Sudeep Holla <[e-mail]>

Once the error path issues pointed by Ulf are resolved,

Reviewed-by: Sudeep Holla <[e-mail]>

> Cc: Daniel Lezcano <[e-mail]>
> Cc: Mark Rutland <[e-mail]>
> Cc: "Rafael J. Wysocki" <[e-mail]>
> ---
>  MAINTAINERS                    |   8 ++
>  drivers/cpuidle/Kconfig.arm    |   3 +
>  drivers/cpuidle/Makefile       |   1 +
>  drivers/cpuidle/cpuidle-psci.c | 150 +++++++++++++++++++++++++++++++++
>  4 files changed, 162 insertions(+)
>  create mode 100644 drivers/cpuidle/cpuidle-psci.c
>
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 783569e3c4b4..c2bf8ce65e83 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -4286,6 +4286,14 @@ S:	Supported
>  F:	drivers/cpuidle/cpuidle-exynos.c
>  F:	arch/arm/mach-exynos/pm.c
>
> +CPUIDLE DRIVER - ARM PSCI
> +M:	Lorenzo Pieralisi <[e-mail]>
> +M:	Sudeep Holla <[e-mail]>
> +L:	[e-mail]
> +L:	[e-mail]
> +S:	Supported
> +F:	drivers/cpuidle/cpuidle-psci.c
> +
>  CPU IDLE TIME MANAGEMENT FRAMEWORK
>  M:	"Rafael J. Wysocki" <[e-mail]>
>  M:	Daniel Lezcano <[e-mail]>
> diff --git a/drivers/cpuidle/Kconfig.arm b/drivers/cpuidle/Kconfig.arm
> index 48cb3d4bb7d1..929b57424ea4 100644
> --- a/drivers/cpuidle/Kconfig.arm
> +++ b/drivers/cpuidle/Kconfig.arm
> @@ -13,6 +13,9 @@ config ARM_CPUIDLE
>            initialized by calling the CPU operations init idle hook
>            provided by architecture code.
>
> +config ARM_PSCI_CPUIDLE
> +	bool
> +

[nit] I understand the intention to keep it hidden, but can't we have
the dependency and selection of other config as part of this patch to
make it more complete ?

--
Regards,
Sudeep

Lorenzo Pieralisi Aug. 6, 2019, 4:34 p.m. UTC | #4

On Tue, Aug 06, 2019 at 05:10:33PM +0100, Sudeep Holla wrote:
> On Mon, Jul 22, 2019 at 04:37:43PM +0100, Lorenzo Pieralisi wrote:
> > 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: Lorenzo Pieralisi <[e-mail]>
> > Cc: Ulf Hansson <[e-mail]>
> > Cc: Sudeep Holla <[e-mail]>
> 
> Once the error path issues pointed by Ulf are resolved,
> 
> Reviewed-by: Sudeep Holla <[e-mail]>
> 
> > Cc: Daniel Lezcano <[e-mail]>
> > Cc: Mark Rutland <[e-mail]>
> > Cc: "Rafael J. Wysocki" <[e-mail]>
> > ---
> >  MAINTAINERS                    |   8 ++
> >  drivers/cpuidle/Kconfig.arm    |   3 +
> >  drivers/cpuidle/Makefile       |   1 +
> >  drivers/cpuidle/cpuidle-psci.c | 150 +++++++++++++++++++++++++++++++++
> >  4 files changed, 162 insertions(+)
> >  create mode 100644 drivers/cpuidle/cpuidle-psci.c
> >
> > diff --git a/MAINTAINERS b/MAINTAINERS
> > index 783569e3c4b4..c2bf8ce65e83 100644
> > --- a/MAINTAINERS
> > +++ b/MAINTAINERS
> > @@ -4286,6 +4286,14 @@ S:	Supported
> >  F:	drivers/cpuidle/cpuidle-exynos.c
> >  F:	arch/arm/mach-exynos/pm.c
> >
> > +CPUIDLE DRIVER - ARM PSCI
> > +M:	Lorenzo Pieralisi <[e-mail]>
> > +M:	Sudeep Holla <[e-mail]>
> > +L:	[e-mail]
> > +L:	[e-mail]
> > +S:	Supported
> > +F:	drivers/cpuidle/cpuidle-psci.c
> > +
> >  CPU IDLE TIME MANAGEMENT FRAMEWORK
> >  M:	"Rafael J. Wysocki" <[e-mail]>
> >  M:	Daniel Lezcano <[e-mail]>
> > diff --git a/drivers/cpuidle/Kconfig.arm b/drivers/cpuidle/Kconfig.arm
> > index 48cb3d4bb7d1..929b57424ea4 100644
> > --- a/drivers/cpuidle/Kconfig.arm
> > +++ b/drivers/cpuidle/Kconfig.arm
> > @@ -13,6 +13,9 @@ config ARM_CPUIDLE
> >            initialized by calling the CPU operations init idle hook
> >            provided by architecture code.
> >
> > +config ARM_PSCI_CPUIDLE
> > +	bool
> > +
> 
> [nit] I understand the intention to keep it hidden, but can't we have
> the dependency and selection of other config as part of this patch to
> make it more complete ?

Yes we can, it makes sense.

Thanks,
Lorenzo

Daniel Lezcano Aug. 7, 2019, 4:30 p.m. UTC | #5

On 22/07/2019 17:37, Lorenzo Pieralisi wrote:
> 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: Lorenzo Pieralisi <[e-mail]>
> Cc: Ulf Hansson <[e-mail]>
> Cc: Sudeep Holla <[e-mail]>
> Cc: Daniel Lezcano <[e-mail]>
> Cc: Mark Rutland <[e-mail]>
> Cc: "Rafael J. Wysocki" <[e-mail]>
> ---

Modulo Ulf and Sudeep comments,

Acked-by: Daniel Lezcano <[e-mail]>

Patch

diff --git a/MAINTAINERS b/MAINTAINERS
index 783569e3c4b4..c2bf8ce65e83 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -4286,6 +4286,14 @@  S:	Supported
 F:	drivers/cpuidle/cpuidle-exynos.c
 F:	arch/arm/mach-exynos/pm.c
 
+CPUIDLE DRIVER - ARM PSCI
+M:	Lorenzo Pieralisi <[e-mail]>
+M:	Sudeep Holla <[e-mail]>
+L:	[e-mail]
+L:	[e-mail]
+S:	Supported
+F:	drivers/cpuidle/cpuidle-psci.c
+
 CPU IDLE TIME MANAGEMENT FRAMEWORK
 M:	"Rafael J. Wysocki" <[e-mail]>
 M:	Daniel Lezcano <[e-mail]>
diff --git a/drivers/cpuidle/Kconfig.arm b/drivers/cpuidle/Kconfig.arm
index 48cb3d4bb7d1..929b57424ea4 100644
--- a/drivers/cpuidle/Kconfig.arm
+++ b/drivers/cpuidle/Kconfig.arm
@@ -13,6 +13,9 @@  config ARM_CPUIDLE
           initialized by calling the CPU operations init idle hook
           provided by architecture code.
 
+config ARM_PSCI_CPUIDLE
+	bool
+
 config ARM_BIG_LITTLE_CPUIDLE
 	bool "Support for ARM big.LITTLE processors"
 	depends on ARCH_VEXPRESS_TC2_PM || ARCH_EXYNOS
diff --git a/drivers/cpuidle/Makefile b/drivers/cpuidle/Makefile
index 9d7176cee3d3..40d016339b29 100644
--- a/drivers/cpuidle/Makefile
+++ b/drivers/cpuidle/Makefile
@@ -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
diff --git a/drivers/cpuidle/cpuidle-psci.c b/drivers/cpuidle/cpuidle-psci.c
new file mode 100644
index 000000000000..bdf02600e4e2
--- /dev/null
+++ b/drivers/cpuidle/cpuidle-psci.c
@@ -0,0 +1,150 @@ 
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * PSCI CPU idle driver.
+ *
+ * Copyright (C) 2019 ARM Ltd.
+ * Author: Lorenzo Pieralisi <[e-mail]>
+ */
+
+#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/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;
+
+	drv = kmemdup(&psci_idle_driver, sizeof(*drv), GFP_KERNEL);
+	if (!drv)
+		return -ENOMEM;
+
+	drv->cpumask = (struct cpumask *)cpumask_of(cpu);
+
+	cpu_node = of_get_cpu_node(cpu, NULL);
+	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;
+
+	/*
+	 * 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);