[PATCH v2] dt: update PSCI binding documentation for v0.2
Rob Herring
robherring2 at gmail.com
Fri Aug 23 15:30:44 EDT 2013
On 08/23/2013 12:24 PM, Mark Rutland wrote:
> On Fri, Aug 23, 2013 at 04:10:13PM +0100, Rob Herring wrote:
>> From: Rob Herring <rob.herring at calxeda.com>
>>
>> The PSCI spec from ARM has been updated to 0.2 version. Update the
>> binding document to reflect the spec changes. For the binding, the
>> major changes are addition of system reset and poweroff functions.
>> The recommended function id numbering has also changed.
>>
>> This update also defines 32 and 64 bit calling conventions. The calling
>> convention is defined by the method property.
>>
>> Signed-off-by: Rob Herring <rob.herring at calxeda.com>
>> Cc: Dave Martin <Dave.Martin at arm.com>
>> Cc: Mark Rutland <mark.rutland at arm.com>
>> Cc: Ian Campbell <Ian.Campbell at citrix.com>
>> Cc: Stefano Stabellini <stefano.stabellini at eu.citrix.com>
>> Cc: Marc Zyngier <Marc.Zyngier at arm.com>
>> Cc: Christoffer Dall <christoffer.dall at linaro.org>,
>> Cc: Charles Garcia-Tobin <Charles.Garcia-Tobin at arm.com>
>> Cc: Matt Sealey <neko at bakuhatsu.net>
>> Cc: devicetree at vger.kernel.org
>> ---
>> Documentation/devicetree/bindings/arm/psci.txt | 85 +++++++++++++++++++++-----
>> 1 file changed, 69 insertions(+), 16 deletions(-)
>>
>> diff --git a/Documentation/devicetree/bindings/arm/psci.txt b/Documentation/devicetree/bindings/arm/psci.txt
>> index 433afe9..2c03d0b 100644
>> --- a/Documentation/devicetree/bindings/arm/psci.txt
>> +++ b/Documentation/devicetree/bindings/arm/psci.txt
>> @@ -1,16 +1,17 @@
>> * 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
>> +ARM DEN 0022B ("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.
>> +Issue B of the specification describes functions for CPU suspend, hotplug,
>> +migration of secure software, and system level reset and powerdown.
>>
>> 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:
>> +as defined in ARM document "SMC Calling Convention" (ARM DEN 0028) in a manner
>> +similar to that specified by AAPCS:
>>
>> r0 => 32-bit Function ID / return value
>> {r1 - r3} => Parameters
>> @@ -21,16 +22,37 @@ to #0.
>>
>> Main node required properties:
>>
>> - - compatible : Must be "arm,psci"
>> + - compatible : Must be "arm,psci-0.2" or "arm,psci"
>>
>> - - method : The method of calling the PSCI firmware. Permitted
>> - values are:
>> + - method : The method defines the calling convention for the PSCI
>> + firmware. If the firmware supports multiple calling
>> + conventions (i.e. 32 and 64 bit), then the DT shall have a
>> + node for each method. Permitted values are:
>
> I really don't see the point in a node per method when I described how
> we could handle this in a single node last time [1], in a way that was
> backwards-compatible with the existing binding.
>
>>
>> "smc" : SMC #0, with the register assignments specified
>> - in this binding.
>> + in this binding (deprecated, "arm,psci" only).
>> +
>> + "smc32" : SMC #0, using 32-bit SMC calling convention with
>> + 32-bit register assignments specified in this
>> + binding.
>> +
>> + "smc64" : SMC #0, using 64-bit SMC calling convention with
>> + 64-bit register assignments specified in this
>> + binding.
>>
>> "hvc" : HVC #0, with the register assignments specified
>> - in this binding.
>> + in this binding (deprecated, "arm,psci" only).
>> +
>> + "hvc32" : HVC #0, using 32-bit HVC calling convention with
>> + 32-bit register assignments specified in this
>> + binding.
>> +
>> + "hvc64" : HVC #0, using 64-bit HVCC calling convention with
>> + 64-bit register assignments specified in this
>> + binding.
>
> I also don't think the bit-widths of function IDs are a property of the
> conduit used.
Right, function IDs are 32-bit, but the register arguments can be 64-bit.
>
>> +
>> + - psci_version : Function ID for PSCI_VERSION operation. Required for
>> + "arm,psci-0.2" compatible version or later.
>>
>> Main node optional properties:
>>
>> @@ -40,16 +62,47 @@ Main node optional properties:
>>
>> - cpu_on : Function ID for CPU_ON operation
>>
>> + - affinity_info : Function ID for AFFINITY_INFO operation
>> +
>> - migrate : Function ID for MIGRATE operation
>>
>> + - migrate_info_type : Function ID for MIGRATE_INFO_TYPE operation
>> +
>> + - migrate_info_up_cpu : Function ID for MIGRATE_INFO_UP_CPU operation
>> +
>> + - system_reset : Function ID for SYSTEM_RESET operation
>> +
>> + - system_off : Function ID for SYSTEM_OFF operation
>> +
>>
>> Example:
>>
>> - psci {
>> - compatible = "arm,psci";
>> - method = "smc";
>> - cpu_suspend = <0x95c10000>;
>> - cpu_off = <0x95c10001>;
>> - cpu_on = <0x95c10002>;
>> - migrate = <0x95c10003>;
>> + psci32 {
>> + compatible = "arm,psci-0.2";
>> + method = "smc32";
>> + psci_version = <0x84000000>;
>> + cpu_suspend = <0x84000001>;
>> + cpu_off = <0x84000002>;
>> + cpu_on = <0x84000003>;
>> + affinity_info = <0x84000004>;
>> + migrate = <0x84000005>;
>> + migrate_info_type = <0x84000006>;
>> + migrate_info_up_cpu = <0x84000007>;
>> + system_off = <0x84000008>;
>> + system_reset = <0x84000009>;
>> + };
>> +
>> + psci64 {
>> + compatible = "arm,psci-0.2";
>> + method = "smc64";
>> + psci_version = <0x84000000>;
>> + cpu_suspend = <0xc4000001>;
>> + cpu_off = <0x84000002>;
>> + cpu_on = <0xc4000003>;
>> + affinity_info = <0xc4000004>;
>> + migrate = <0xc4000005>;
>> + migrate_info_type = <0x84000006>;
>> + migrate_info_up_cpu = <0xc4000007>;
>> + system_off = <0x84000008>;
>> + system_reset = <0x84000009>;
>> };
>
> With that style of binding we can't use a new DT with an old kernel,
> despite the fact the actual firmware interface is compatible. I believe
> having this as one node, with $FUNCTION, $FUNCTION-32, and $FUNCTION-64
> variants makes much more sense.
>
> Consider KVM. If we want to provide new functionality (e.g.
> affinity_info) without breaking compatibility with older kernels, we'd
> have to embed three device nodes repeatedly describing the same IDs.
> That's a complete waste when we can handle this in a single node, taking
> up less space with some degree of forwards compatibility:
I don't really have a strong opinion either way. I happen to prefer
multiple nodes as Matt had proposed, but am okay with this. I really
just want to get system reset and off added so I can finish highbank
support.
> psci {
> compatible = "arm,psci-0.2", "arm,psci";
> method = "smc";
>
> /* common IDs for 32-bit and 64-bit */
> cpu_off = <0x1>;
> cpu_on = <0x2>;
> cpu_suspend = <0x3>;
>
> /* different IDs for 64-bit and 32-bit */
> psci_version32 = <0xbbbb>;
> psci_version64 = <0xdddd>;
According to the spec, psci_version is the same for 32 and 64-bit. For
functions like that, do we need to specify the size?
Rob
> migrate_info_type32 = <0x57>;
> migrate_info_type64 = <0xb7>;
> };
>
> Thanks,
> Mark.
>
> [1] http://lists.infradead.org/pipermail/linux-arm-kernel/2013-July/187725.html
>
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