diff mbox

[v10,10/21] ARM64 / ACPI: Get PSCI flags in FADT for PSCI init

Message ID 1426077587-1561-11-git-send-email-hanjun.guo@linaro.org (mailing list archive)
State New, archived
Headers show

Commit Message

Hanjun Guo March 11, 2015, 12:39 p.m. UTC 
From: Graeme Gregory <graeme.gregory@linaro.org>

There are two flags: PSCI_COMPLIANT and PSCI_USE_HVC. When set,
the former signals to the OS that the firmware is PSCI compliant.
The latter selects the appropriate conduit for PSCI calls by
toggling between Hypervisor Calls (HVC) and Secure Monitor Calls
(SMC).

FADT table contains such information in ACPI 5.1, FADT table was
parsed in ACPI table init and copy to struct acpi_gbl_FADT, so
use the flags in struct acpi_gbl_FADT for PSCI init.

Since ACPI 5.1 doesn't support self defined PSCI function IDs,
which means that only PSCI 0.2+ is supported in ACPI.

CC: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
CC: Catalin Marinas <catalin.marinas@arm.com>
CC: Will Deacon <will.deacon@arm.com>
Tested-by: Suravee Suthikulpanit <Suravee.Suthikulpanit@amd.com>
Tested-by: Yijing Wang <wangyijing@huawei.com>
Tested-by: Mark Langsdorf <mlangsdo@redhat.com>
Tested-by: Jon Masters <jcm@redhat.com>
Tested-by: Timur Tabi <timur@codeaurora.org>
Tested-by: Robert Richter <rrichter@cavium.com>
Acked-by: Robert Richter <rrichter@cavium.com>
Acked-by: Olof Johansson <olof@lixom.net>
Acked-by: Grant Likely <grant.likely@linaro.org>
Signed-off-by: Graeme Gregory <graeme.gregory@linaro.org>
Signed-off-by: Tomasz Nowicki <tomasz.nowicki@linaro.org>
Signed-off-by: Hanjun Guo <hanjun.guo@linaro.org>
---
 arch/arm64/include/asm/acpi.h | 15 +++++++++
 arch/arm64/include/asm/psci.h |  3 +-
 arch/arm64/kernel/psci.c      | 78 ++++++++++++++++++++++++++++++-------------
 arch/arm64/kernel/setup.c     |  8 +++--
 4 files changed, 76 insertions(+), 28 deletions(-)

Comments

Lorenzo Pieralisi March 13, 2015, 2:51 p.m. UTC | #1 
On Wed, Mar 11, 2015 at 12:39:36PM +0000, Hanjun Guo wrote:

[...]

> +static void __init psci_0_2_set_functions(void)
> +{
> +	pr_info("Using standard PSCI v0.2 function IDs\n");
> +	psci_function_id[PSCI_FN_CPU_SUSPEND] = PSCI_0_2_FN64_CPU_SUSPEND;
> +	psci_ops.cpu_suspend = psci_cpu_suspend;
> +
> +	psci_function_id[PSCI_FN_CPU_OFF] = PSCI_0_2_FN_CPU_OFF;
> +	psci_ops.cpu_off = psci_cpu_off;
> +
> +	psci_function_id[PSCI_FN_CPU_ON] = PSCI_0_2_FN64_CPU_ON;
> +	psci_ops.cpu_on = psci_cpu_on;
> +
> +	psci_function_id[PSCI_FN_MIGRATE] = PSCI_0_2_FN64_MIGRATE;
> +	psci_ops.migrate = psci_migrate;
> +
> +	psci_function_id[PSCI_FN_AFFINITY_INFO] = PSCI_0_2_FN64_AFFINITY_INFO;
> +	psci_ops.affinity_info = psci_affinity_info;
> +
> +	psci_function_id[PSCI_FN_MIGRATE_INFO_TYPE] =
> +		PSCI_0_2_FN_MIGRATE_INFO_TYPE;
> +	psci_ops.migrate_info_type = psci_migrate_info_type;
> +
> +	arm_pm_restart = psci_sys_reset;
> +
> +	pm_power_off = psci_sys_poweroff;
> +}
> +
>  /*
>   * PSCI Function IDs for v0.2+ are well defined so use
>   * standard values.
> @@ -306,29 +335,7 @@ static int __init psci_0_2_init(struct device_node *np)
>  		}
>  	}
>  
> -	pr_info("Using standard PSCI v0.2 function IDs\n");
> -	psci_function_id[PSCI_FN_CPU_SUSPEND] = PSCI_0_2_FN64_CPU_SUSPEND;
> -	psci_ops.cpu_suspend = psci_cpu_suspend;
> -
> -	psci_function_id[PSCI_FN_CPU_OFF] = PSCI_0_2_FN_CPU_OFF;
> -	psci_ops.cpu_off = psci_cpu_off;
> -
> -	psci_function_id[PSCI_FN_CPU_ON] = PSCI_0_2_FN64_CPU_ON;
> -	psci_ops.cpu_on = psci_cpu_on;
> -
> -	psci_function_id[PSCI_FN_MIGRATE] = PSCI_0_2_FN64_MIGRATE;
> -	psci_ops.migrate = psci_migrate;
> -
> -	psci_function_id[PSCI_FN_AFFINITY_INFO] = PSCI_0_2_FN64_AFFINITY_INFO;
> -	psci_ops.affinity_info = psci_affinity_info;
> -
> -	psci_function_id[PSCI_FN_MIGRATE_INFO_TYPE] =
> -		PSCI_0_2_FN_MIGRATE_INFO_TYPE;
> -	psci_ops.migrate_info_type = psci_migrate_info_type;
> -
> -	arm_pm_restart = psci_sys_reset;
> -
> -	pm_power_off = psci_sys_poweroff;
> +	psci_0_2_set_functions();

You should have factored out the firmware version probing too, that's
the only way we can detect the PSCI firmware version when booting through
ACPI. You can end up initializing pointers for v0.2+ with a mismatching
version implemented in PSCI firmware, eg 0.1.

We should do that incrementally, I will put together a patch to
factor out the FW version probing first, you can rebase on top of it.

>  out_put_node:
>  	of_node_put(np);
> @@ -381,7 +388,7 @@ static const struct of_device_id psci_of_match[] __initconst = {
>  	{},
>  };
>  
> -int __init psci_init(void)
> +int __init psci_dt_init(void)
>  {
>  	struct device_node *np;
>  	const struct of_device_id *matched_np;
> @@ -396,6 +403,29 @@ int __init psci_init(void)
>  	return init_fn(np);
>  }
>  
> +/*
> + * We use PSCI 0.2+ when ACPI is deployed on ARM64 and it's
> + * explicitly clarified in SBBR
> + */
> +int __init psci_acpi_init(void)
> +{
> +	if (!acpi_psci_present()) {
> +		pr_info("is not implemented in ACPI.\n");
> +		return -EOPNOTSUPP;
> +	}

If PSCI is not present, that's a problem related to SMP init, right ?
That's where a warning should be printed if any, not here, the SBBR
mandates PSCI as secondaries bring up method, warn otherwise.

Lorenzo
Hanjun Guo March 16, 2015, 11:45 a.m. UTC | #2 
On 2015?03?13? 22:51, Lorenzo Pieralisi wrote:
> On Wed, Mar 11, 2015 at 12:39:36PM +0000, Hanjun Guo wrote:
>
> [...]
>
>> +static void __init psci_0_2_set_functions(void)
>> +{
>> +	pr_info("Using standard PSCI v0.2 function IDs\n");
>> +	psci_function_id[PSCI_FN_CPU_SUSPEND] = PSCI_0_2_FN64_CPU_SUSPEND;
>> +	psci_ops.cpu_suspend = psci_cpu_suspend;
>> +
>> +	psci_function_id[PSCI_FN_CPU_OFF] = PSCI_0_2_FN_CPU_OFF;
>> +	psci_ops.cpu_off = psci_cpu_off;
>> +
>> +	psci_function_id[PSCI_FN_CPU_ON] = PSCI_0_2_FN64_CPU_ON;
>> +	psci_ops.cpu_on = psci_cpu_on;
>> +
>> +	psci_function_id[PSCI_FN_MIGRATE] = PSCI_0_2_FN64_MIGRATE;
>> +	psci_ops.migrate = psci_migrate;
>> +
>> +	psci_function_id[PSCI_FN_AFFINITY_INFO] = PSCI_0_2_FN64_AFFINITY_INFO;
>> +	psci_ops.affinity_info = psci_affinity_info;
>> +
>> +	psci_function_id[PSCI_FN_MIGRATE_INFO_TYPE] =
>> +		PSCI_0_2_FN_MIGRATE_INFO_TYPE;
>> +	psci_ops.migrate_info_type = psci_migrate_info_type;
>> +
>> +	arm_pm_restart = psci_sys_reset;
>> +
>> +	pm_power_off = psci_sys_poweroff;
>> +}
>> +
>>   /*
>>    * PSCI Function IDs for v0.2+ are well defined so use
>>    * standard values.
>> @@ -306,29 +335,7 @@ static int __init psci_0_2_init(struct device_node *np)
>>   		}
>>   	}
>>
>> -	pr_info("Using standard PSCI v0.2 function IDs\n");
>> -	psci_function_id[PSCI_FN_CPU_SUSPEND] = PSCI_0_2_FN64_CPU_SUSPEND;
>> -	psci_ops.cpu_suspend = psci_cpu_suspend;
>> -
>> -	psci_function_id[PSCI_FN_CPU_OFF] = PSCI_0_2_FN_CPU_OFF;
>> -	psci_ops.cpu_off = psci_cpu_off;
>> -
>> -	psci_function_id[PSCI_FN_CPU_ON] = PSCI_0_2_FN64_CPU_ON;
>> -	psci_ops.cpu_on = psci_cpu_on;
>> -
>> -	psci_function_id[PSCI_FN_MIGRATE] = PSCI_0_2_FN64_MIGRATE;
>> -	psci_ops.migrate = psci_migrate;
>> -
>> -	psci_function_id[PSCI_FN_AFFINITY_INFO] = PSCI_0_2_FN64_AFFINITY_INFO;
>> -	psci_ops.affinity_info = psci_affinity_info;
>> -
>> -	psci_function_id[PSCI_FN_MIGRATE_INFO_TYPE] =
>> -		PSCI_0_2_FN_MIGRATE_INFO_TYPE;
>> -	psci_ops.migrate_info_type = psci_migrate_info_type;
>> -
>> -	arm_pm_restart = psci_sys_reset;
>> -
>> -	pm_power_off = psci_sys_poweroff;
>> +	psci_0_2_set_functions();
>
> You should have factored out the firmware version probing too, that's
> the only way we can detect the PSCI firmware version when booting through
> ACPI. You can end up initializing pointers for v0.2+ with a mismatching
> version implemented in PSCI firmware, eg 0.1.
>
> We should do that incrementally, I will put together a patch to
> factor out the FW version probing first, you can rebase on top of it.

Incrementally patches on top of this patch set? I think v10 of this
patch set is ready for merge, but I'm open for suggestions if we will
not miss the merge window for Catalin.

>
>>   out_put_node:
>>   	of_node_put(np);
>> @@ -381,7 +388,7 @@ static const struct of_device_id psci_of_match[] __initconst = {
>>   	{},
>>   };
>>
>> -int __init psci_init(void)
>> +int __init psci_dt_init(void)
>>   {
>>   	struct device_node *np;
>>   	const struct of_device_id *matched_np;
>> @@ -396,6 +403,29 @@ int __init psci_init(void)
>>   	return init_fn(np);
>>   }
>>
>> +/*
>> + * We use PSCI 0.2+ when ACPI is deployed on ARM64 and it's
>> + * explicitly clarified in SBBR
>> + */
>> +int __init psci_acpi_init(void)
>> +{
>> +	if (!acpi_psci_present()) {
>> +		pr_info("is not implemented in ACPI.\n");
>> +		return -EOPNOTSUPP;
>> +	}
>
> If PSCI is not present, that's a problem related to SMP init, right ?
> That's where a warning should be printed if any, not here, the SBBR
> mandates PSCI as secondaries bring up method, warn otherwise.

The SBBR is also said that if PSCI is not available, Parking protocol
will be used as secondaries bring up method, so I said that it is ok
to me that we don't print warn message for no PSCI support when parsing
FADT.

So maybe we can go back to the previous solution, print some warning
message if no PSCI when parsing FADT?

Thanks
Hanjun
Lorenzo Pieralisi March 16, 2015, 6:41 p.m. UTC | #3 
On Mon, Mar 16, 2015 at 11:45:25AM +0000, Hanjun Guo wrote:
> On 2015?03?13? 22:51, Lorenzo Pieralisi wrote:
> > On Wed, Mar 11, 2015 at 12:39:36PM +0000, Hanjun Guo wrote:
> >
> > [...]
> >
> >> +static void __init psci_0_2_set_functions(void)
> >> +{
> >> +	pr_info("Using standard PSCI v0.2 function IDs\n");
> >> +	psci_function_id[PSCI_FN_CPU_SUSPEND] = PSCI_0_2_FN64_CPU_SUSPEND;
> >> +	psci_ops.cpu_suspend = psci_cpu_suspend;
> >> +
> >> +	psci_function_id[PSCI_FN_CPU_OFF] = PSCI_0_2_FN_CPU_OFF;
> >> +	psci_ops.cpu_off = psci_cpu_off;
> >> +
> >> +	psci_function_id[PSCI_FN_CPU_ON] = PSCI_0_2_FN64_CPU_ON;
> >> +	psci_ops.cpu_on = psci_cpu_on;
> >> +
> >> +	psci_function_id[PSCI_FN_MIGRATE] = PSCI_0_2_FN64_MIGRATE;
> >> +	psci_ops.migrate = psci_migrate;
> >> +
> >> +	psci_function_id[PSCI_FN_AFFINITY_INFO] = PSCI_0_2_FN64_AFFINITY_INFO;
> >> +	psci_ops.affinity_info = psci_affinity_info;
> >> +
> >> +	psci_function_id[PSCI_FN_MIGRATE_INFO_TYPE] =
> >> +		PSCI_0_2_FN_MIGRATE_INFO_TYPE;
> >> +	psci_ops.migrate_info_type = psci_migrate_info_type;
> >> +
> >> +	arm_pm_restart = psci_sys_reset;
> >> +
> >> +	pm_power_off = psci_sys_poweroff;
> >> +}
> >> +
> >>   /*
> >>    * PSCI Function IDs for v0.2+ are well defined so use
> >>    * standard values.
> >> @@ -306,29 +335,7 @@ static int __init psci_0_2_init(struct device_node *np)
> >>   		}
> >>   	}
> >>
> >> -	pr_info("Using standard PSCI v0.2 function IDs\n");
> >> -	psci_function_id[PSCI_FN_CPU_SUSPEND] = PSCI_0_2_FN64_CPU_SUSPEND;
> >> -	psci_ops.cpu_suspend = psci_cpu_suspend;
> >> -
> >> -	psci_function_id[PSCI_FN_CPU_OFF] = PSCI_0_2_FN_CPU_OFF;
> >> -	psci_ops.cpu_off = psci_cpu_off;
> >> -
> >> -	psci_function_id[PSCI_FN_CPU_ON] = PSCI_0_2_FN64_CPU_ON;
> >> -	psci_ops.cpu_on = psci_cpu_on;
> >> -
> >> -	psci_function_id[PSCI_FN_MIGRATE] = PSCI_0_2_FN64_MIGRATE;
> >> -	psci_ops.migrate = psci_migrate;
> >> -
> >> -	psci_function_id[PSCI_FN_AFFINITY_INFO] = PSCI_0_2_FN64_AFFINITY_INFO;
> >> -	psci_ops.affinity_info = psci_affinity_info;
> >> -
> >> -	psci_function_id[PSCI_FN_MIGRATE_INFO_TYPE] =
> >> -		PSCI_0_2_FN_MIGRATE_INFO_TYPE;
> >> -	psci_ops.migrate_info_type = psci_migrate_info_type;
> >> -
> >> -	arm_pm_restart = psci_sys_reset;
> >> -
> >> -	pm_power_off = psci_sys_poweroff;
> >> +	psci_0_2_set_functions();
> >
> > You should have factored out the firmware version probing too, that's
> > the only way we can detect the PSCI firmware version when booting through
> > ACPI. You can end up initializing pointers for v0.2+ with a mismatching
> > version implemented in PSCI firmware, eg 0.1.
> >
> > We should do that incrementally, I will put together a patch to
> > factor out the FW version probing first, you can rebase on top of it.
> 
> Incrementally patches on top of this patch set? I think v10 of this
> patch set is ready for merge, but I'm open for suggestions if we will
> not miss the merge window for Catalin.

I gave you my suggestion, I will try to get the prerequisite patch
queued asap, it is not a big deal but that's something that should be
fixed otherwise I would not have flagged this up.

I will post the patch asap, if we fail to get that in we will see what
to do, I do not expect this to be a blocking point.

> >
> >>   out_put_node:
> >>   	of_node_put(np);
> >> @@ -381,7 +388,7 @@ static const struct of_device_id psci_of_match[] __initconst = {
> >>   	{},
> >>   };
> >>
> >> -int __init psci_init(void)
> >> +int __init psci_dt_init(void)
> >>   {
> >>   	struct device_node *np;
> >>   	const struct of_device_id *matched_np;
> >> @@ -396,6 +403,29 @@ int __init psci_init(void)
> >>   	return init_fn(np);
> >>   }
> >>
> >> +/*
> >> + * We use PSCI 0.2+ when ACPI is deployed on ARM64 and it's
> >> + * explicitly clarified in SBBR
> >> + */
> >> +int __init psci_acpi_init(void)
> >> +{
> >> +	if (!acpi_psci_present()) {
> >> +		pr_info("is not implemented in ACPI.\n");
> >> +		return -EOPNOTSUPP;
> >> +	}
> >
> > If PSCI is not present, that's a problem related to SMP init, right ?
> > That's where a warning should be printed if any, not here, the SBBR
> > mandates PSCI as secondaries bring up method, warn otherwise.
> 
> The SBBR is also said that if PSCI is not available, Parking protocol
> will be used as secondaries bring up method, so I said that it is ok
> to me that we don't print warn message for no PSCI support when parsing
> FADT.
> 
> So maybe we can go back to the previous solution, print some warning
> message if no PSCI when parsing FADT?

You answered your own question. It is not what it is mandated, but if
a platform boots with parking protocol, do you think the information
you are printing in:

if (!acpi_psci_present()) {
	pr_info("is not implemented in ACPI.\n");
        ^^^

is useful to them ?

What should be flagged up is a missing boot method for secondaries,
a missing PSCI is not per-se an error, that's why I said it should
be done when preparing CPUs for SMP init.

No big deal at all, but I would remove the pr_info above.

Lorenzo
diff mbox

Patch

diff --git a/arch/arm64/include/asm/acpi.h b/arch/arm64/include/asm/acpi.h
index c5a9b97..9ea650c 100644
--- a/arch/arm64/include/asm/acpi.h
+++ b/arch/arm64/include/asm/acpi.h
@@ -32,6 +32,18 @@  extern int acpi_disabled;
 extern int acpi_noirq;
 extern int acpi_pci_disabled;
 
+/* 1 to indicate PSCI 0.2+ is implemented */
+static inline bool acpi_psci_present(void)
+{
+	return acpi_gbl_FADT.arm_boot_flags & ACPI_FADT_PSCI_COMPLIANT;
+}
+
+/* 1 to indicate HVC must be used instead of SMC as the PSCI conduit */
+static inline bool acpi_psci_use_hvc(void)
+{
+	return acpi_gbl_FADT.arm_boot_flags & ACPI_FADT_PSCI_USE_HVC;
+}
+
 static inline void disable_acpi(void)
 {
 	acpi_disabled = 1;
@@ -60,6 +72,9 @@  static inline bool acpi_has_cpu_in_madt(void)
 
 static inline void arch_fix_phys_package_id(int num, u32 slot) { }
 
+#else
+static inline bool acpi_psci_present(void) { return false; }
+static inline bool acpi_psci_use_hvc(void) { return false; }
 #endif /* CONFIG_ACPI */
 
 #endif /*_ASM_ACPI_H*/
diff --git a/arch/arm64/include/asm/psci.h b/arch/arm64/include/asm/psci.h
index e5312ea..2454bc5 100644
--- a/arch/arm64/include/asm/psci.h
+++ b/arch/arm64/include/asm/psci.h
@@ -14,6 +14,7 @@ 
 #ifndef __ASM_PSCI_H
 #define __ASM_PSCI_H
 
-int psci_init(void);
+int psci_dt_init(void);
+int psci_acpi_init(void);
 
 #endif /* __ASM_PSCI_H */
diff --git a/arch/arm64/kernel/psci.c b/arch/arm64/kernel/psci.c
index 9b8a70a..d3c52ce 100644
--- a/arch/arm64/kernel/psci.c
+++ b/arch/arm64/kernel/psci.c
@@ -15,6 +15,7 @@ 
 
 #define pr_fmt(fmt) "psci: " fmt
 
+#include <linux/acpi.h>
 #include <linux/init.h>
 #include <linux/of.h>
 #include <linux/smp.h>
@@ -24,6 +25,7 @@ 
 #include <linux/slab.h>
 #include <uapi/linux/psci.h>
 
+#include <asm/acpi.h>
 #include <asm/compiler.h>
 #include <asm/cpu_ops.h>
 #include <asm/errno.h>
@@ -273,6 +275,33 @@  static void psci_sys_poweroff(void)
 	invoke_psci_fn(PSCI_0_2_FN_SYSTEM_OFF, 0, 0, 0);
 }
 
+static void __init psci_0_2_set_functions(void)
+{
+	pr_info("Using standard PSCI v0.2 function IDs\n");
+	psci_function_id[PSCI_FN_CPU_SUSPEND] = PSCI_0_2_FN64_CPU_SUSPEND;
+	psci_ops.cpu_suspend = psci_cpu_suspend;
+
+	psci_function_id[PSCI_FN_CPU_OFF] = PSCI_0_2_FN_CPU_OFF;
+	psci_ops.cpu_off = psci_cpu_off;
+
+	psci_function_id[PSCI_FN_CPU_ON] = PSCI_0_2_FN64_CPU_ON;
+	psci_ops.cpu_on = psci_cpu_on;
+
+	psci_function_id[PSCI_FN_MIGRATE] = PSCI_0_2_FN64_MIGRATE;
+	psci_ops.migrate = psci_migrate;
+
+	psci_function_id[PSCI_FN_AFFINITY_INFO] = PSCI_0_2_FN64_AFFINITY_INFO;
+	psci_ops.affinity_info = psci_affinity_info;
+
+	psci_function_id[PSCI_FN_MIGRATE_INFO_TYPE] =
+		PSCI_0_2_FN_MIGRATE_INFO_TYPE;
+	psci_ops.migrate_info_type = psci_migrate_info_type;
+
+	arm_pm_restart = psci_sys_reset;
+
+	pm_power_off = psci_sys_poweroff;
+}
+
 /*
  * PSCI Function IDs for v0.2+ are well defined so use
  * standard values.
@@ -306,29 +335,7 @@  static int __init psci_0_2_init(struct device_node *np)
 		}
 	}
 
-	pr_info("Using standard PSCI v0.2 function IDs\n");
-	psci_function_id[PSCI_FN_CPU_SUSPEND] = PSCI_0_2_FN64_CPU_SUSPEND;
-	psci_ops.cpu_suspend = psci_cpu_suspend;
-
-	psci_function_id[PSCI_FN_CPU_OFF] = PSCI_0_2_FN_CPU_OFF;
-	psci_ops.cpu_off = psci_cpu_off;
-
-	psci_function_id[PSCI_FN_CPU_ON] = PSCI_0_2_FN64_CPU_ON;
-	psci_ops.cpu_on = psci_cpu_on;
-
-	psci_function_id[PSCI_FN_MIGRATE] = PSCI_0_2_FN64_MIGRATE;
-	psci_ops.migrate = psci_migrate;
-
-	psci_function_id[PSCI_FN_AFFINITY_INFO] = PSCI_0_2_FN64_AFFINITY_INFO;
-	psci_ops.affinity_info = psci_affinity_info;
-
-	psci_function_id[PSCI_FN_MIGRATE_INFO_TYPE] =
-		PSCI_0_2_FN_MIGRATE_INFO_TYPE;
-	psci_ops.migrate_info_type = psci_migrate_info_type;
-
-	arm_pm_restart = psci_sys_reset;
-
-	pm_power_off = psci_sys_poweroff;
+	psci_0_2_set_functions();
 
 out_put_node:
 	of_node_put(np);
@@ -381,7 +388,7 @@  static const struct of_device_id psci_of_match[] __initconst = {
 	{},
 };
 
-int __init psci_init(void)
+int __init psci_dt_init(void)
 {
 	struct device_node *np;
 	const struct of_device_id *matched_np;
@@ -396,6 +403,29 @@  int __init psci_init(void)
 	return init_fn(np);
 }
 
+/*
+ * We use PSCI 0.2+ when ACPI is deployed on ARM64 and it's
+ * explicitly clarified in SBBR
+ */
+int __init psci_acpi_init(void)
+{
+	if (!acpi_psci_present()) {
+		pr_info("is not implemented in ACPI.\n");
+		return -EOPNOTSUPP;
+	}
+
+	pr_info("probing for conduit method from ACPI.\n");
+
+	if (acpi_psci_use_hvc())
+		invoke_psci_fn = __invoke_psci_fn_hvc;
+	else
+		invoke_psci_fn = __invoke_psci_fn_smc;
+
+	psci_0_2_set_functions();
+
+	return 0;
+}
+
 #ifdef CONFIG_SMP
 
 static int __init cpu_psci_cpu_init(struct device_node *dn, unsigned int cpu)
diff --git a/arch/arm64/kernel/setup.c b/arch/arm64/kernel/setup.c
index e8c7000..97fa7f3 100644
--- a/arch/arm64/kernel/setup.c
+++ b/arch/arm64/kernel/setup.c
@@ -390,10 +390,12 @@  void __init setup_arch(char **cmdline_p)
 
 	early_ioremap_reset();
 
-	if (acpi_disabled)
+	if (acpi_disabled) {
 		unflatten_device_tree();
-
-	psci_init();
+		psci_dt_init();
+	} else {
+		psci_acpi_init();
+	}
 
 	cpu_read_bootcpu_ops();
 #ifdef CONFIG_SMP