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linux/Documentation/devicetree/bindings/arm/psci.txt

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ARM: psci: add devicetree binding for describing PSCI firmware This patch adds a new devicetree binding for describing PSCI firmware to Linux. Acked-by: Arnd Bergmann <arnd@arndb.de> Acked-by: Nicolas Pitre <nico@linaro.org> Signed-off-by: Will Deacon <will.deacon@arm.com>
2012-12-12 01:28:27 +08:00
* Power State Coordination Interface (PSCI)
Firmware implementing the PSCI functions described in ARM document number
ARM DEN 0022A ("Power State Coordination Interface System Software on ARM
processors") can be used by Linux to initiate various CPU-centric power
operations.
Issue A of the specification describes functions for CPU suspend, hotplug
and migration of secure software.
Functions are invoked by trapping to the privilege level of the PSCI
firmware (specified as part of the binding below) and passing arguments
in a manner similar to that specified by AAPCS:
r0 => 32-bit Function ID / return value
{r1 - r3} => Parameters
Note that the immediate field of the trapping instruction must be set
to #0.
Main node required properties:
Documentation: devicetree: Add new binding for PSCIv0.2 The PSCI v0.2+ spec defines standard values for PSCI function IDs. Add a new binding entry so that pre v0.2 implementations can use DT entries for function IDs and v0.2+ implementations use standard entries as defined by the PSCIv0.2 specification. Signed-off-by: Ashwin Chaugule <ashwin.chaugule@linaro.org> Reviewed-by: Mark Rutland <mark.rutland@arm.com> Acked-by: Rob Herring <robh@kernel.org> Acked-by: Catalin Marinas <catalin.marinas@arm.com>
2014-03-27 23:08:57 +08:00
- compatible : should contain at least one of:
* "arm,psci" : for implementations complying to PSCI versions prior to
0.2. For these cases function IDs must be provided.
* "arm,psci-0.2" : for implementations complying to PSCI 0.2. Function
IDs are not required and should be ignored by an OS with PSCI 0.2
support, but are permitted to be present for compatibility with
existing software when "arm,psci" is later in the compatible list.
ARM: psci: add devicetree binding for describing PSCI firmware This patch adds a new devicetree binding for describing PSCI firmware to Linux. Acked-by: Arnd Bergmann <arnd@arndb.de> Acked-by: Nicolas Pitre <nico@linaro.org> Signed-off-by: Will Deacon <will.deacon@arm.com>
2012-12-12 01:28:27 +08:00
- method : The method of calling the PSCI firmware. Permitted
values are:
"smc" : SMC #0, with the register assignments specified
in this binding.
"hvc" : HVC #0, with the register assignments specified
in this binding.
Main node optional properties:
- cpu_suspend : Function ID for CPU_SUSPEND operation
- cpu_off : Function ID for CPU_OFF operation
- cpu_on : Function ID for CPU_ON operation
- migrate : Function ID for MIGRATE operation
Documentation: arm: define DT idle states bindings ARM based platforms implement a variety of power management schemes that allow processors to enter idle states at run-time. The parameters defining these idle states vary on a per-platform basis forcing the OS to hardcode the state parameters in platform specific static tables whose size grows as the number of platforms supported in the kernel increases and hampers device drivers standardization. Therefore, this patch aims at standardizing idle state device tree bindings for ARM platforms. Bindings define idle state parameters inclusive of entry methods and state latencies, to allow operating systems to retrieve the configuration entries from the device tree and initialize the related power management drivers, paving the way for common code in the kernel to deal with idle states and removing the need for static data in current and previous kernel versions. ARM64 platforms require the DT to define an entry-method property for idle states. On system implementing PSCI as an enable-method to enter low-power states the PSCI CPU suspend method requires the power_state parameter to be passed to the PSCI CPU suspend function. This parameter is specific to a power state and platform specific, therefore must be provided by firmware to the OS in order to enable proper call sequence. Thus, this patch also adds a property in the PSCI bindings that describes how the PSCI CPU suspend power_state parameter should be defined in DT in all device nodes that rely on PSCI CPU suspend method usage. Acked-by: Catalin Marinas <catalin.marinas@arm.com> Acked-by: Daniel Lezcano <daniel.lezcano@linaro.org> Acked-by: Nicolas Pitre <nico@linaro.org> Reviewed-by: Rob Herring <robh@kernel.org> Reviewed-by: Sebastian Capella <sebcape@gmail.com> Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com> Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
2013-11-28 00:22:55 +08:00
Device tree nodes that require usage of PSCI CPU_SUSPEND function (ie idle
state nodes, as per bindings in [1]) must specify the following properties:
- arm,psci-suspend-param
Usage: Required for state nodes[1] if the corresponding
idle-states node entry-method property is set
to "psci".
Value type: <u32>
Definition: power_state parameter to pass to the PSCI
suspend call.
ARM: psci: add devicetree binding for describing PSCI firmware This patch adds a new devicetree binding for describing PSCI firmware to Linux. Acked-by: Arnd Bergmann <arnd@arndb.de> Acked-by: Nicolas Pitre <nico@linaro.org> Signed-off-by: Will Deacon <will.deacon@arm.com>
2012-12-12 01:28:27 +08:00
Example:
Documentation: devicetree: Add new binding for PSCIv0.2 The PSCI v0.2+ spec defines standard values for PSCI function IDs. Add a new binding entry so that pre v0.2 implementations can use DT entries for function IDs and v0.2+ implementations use standard entries as defined by the PSCIv0.2 specification. Signed-off-by: Ashwin Chaugule <ashwin.chaugule@linaro.org> Reviewed-by: Mark Rutland <mark.rutland@arm.com> Acked-by: Rob Herring <robh@kernel.org> Acked-by: Catalin Marinas <catalin.marinas@arm.com>
2014-03-27 23:08:57 +08:00
Case 1: PSCI v0.1 only.
ARM: psci: add devicetree binding for describing PSCI firmware This patch adds a new devicetree binding for describing PSCI firmware to Linux. Acked-by: Arnd Bergmann <arnd@arndb.de> Acked-by: Nicolas Pitre <nico@linaro.org> Signed-off-by: Will Deacon <will.deacon@arm.com>
2012-12-12 01:28:27 +08:00
psci {
compatible = "arm,psci";
method = "smc";
cpu_suspend = <0x95c10000>;
cpu_off = <0x95c10001>;
cpu_on = <0x95c10002>;
migrate = <0x95c10003>;
};
Documentation: devicetree: Add new binding for PSCIv0.2 The PSCI v0.2+ spec defines standard values for PSCI function IDs. Add a new binding entry so that pre v0.2 implementations can use DT entries for function IDs and v0.2+ implementations use standard entries as defined by the PSCIv0.2 specification. Signed-off-by: Ashwin Chaugule <ashwin.chaugule@linaro.org> Reviewed-by: Mark Rutland <mark.rutland@arm.com> Acked-by: Rob Herring <robh@kernel.org> Acked-by: Catalin Marinas <catalin.marinas@arm.com>
2014-03-27 23:08:57 +08:00
Case 2: PSCI v0.2 only
psci {
compatible = "arm,psci-0.2";
method = "smc";
};
Case 3: PSCI v0.2 and PSCI v0.1.
A DTB may provide IDs for use by kernels without PSCI 0.2 support,
enabling firmware and hypervisors to support existing and new kernels.
These IDs will be ignored by kernels with PSCI 0.2 support, which will
use the standard PSCI 0.2 IDs exclusively.
psci {
compatible = "arm,psci-0.2", "arm,psci";
method = "hvc";
cpu_on = < arbitrary value >;
cpu_off = < arbitrary value >;
...
};
Documentation: arm: define DT idle states bindings ARM based platforms implement a variety of power management schemes that allow processors to enter idle states at run-time. The parameters defining these idle states vary on a per-platform basis forcing the OS to hardcode the state parameters in platform specific static tables whose size grows as the number of platforms supported in the kernel increases and hampers device drivers standardization. Therefore, this patch aims at standardizing idle state device tree bindings for ARM platforms. Bindings define idle state parameters inclusive of entry methods and state latencies, to allow operating systems to retrieve the configuration entries from the device tree and initialize the related power management drivers, paving the way for common code in the kernel to deal with idle states and removing the need for static data in current and previous kernel versions. ARM64 platforms require the DT to define an entry-method property for idle states. On system implementing PSCI as an enable-method to enter low-power states the PSCI CPU suspend method requires the power_state parameter to be passed to the PSCI CPU suspend function. This parameter is specific to a power state and platform specific, therefore must be provided by firmware to the OS in order to enable proper call sequence. Thus, this patch also adds a property in the PSCI bindings that describes how the PSCI CPU suspend power_state parameter should be defined in DT in all device nodes that rely on PSCI CPU suspend method usage. Acked-by: Catalin Marinas <catalin.marinas@arm.com> Acked-by: Daniel Lezcano <daniel.lezcano@linaro.org> Acked-by: Nicolas Pitre <nico@linaro.org> Reviewed-by: Rob Herring <robh@kernel.org> Reviewed-by: Sebastian Capella <sebcape@gmail.com> Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com> Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
2013-11-28 00:22:55 +08:00
[1] Kernel documentation - ARM idle states bindings
Documentation/devicetree/bindings/arm/idle-states.txt