Re: [RFC PATCH v15 02/11] ARM: qcom: Add Subsystem Power Manager (SPM) driver

[Lina Iyer <lina.iyer@linaro.org>]

On Tue, Mar 10 2015 at 11:26 -0600, Kumar Gala wrote:
>
>On Mar 9, 2015, at 10:16 AM, Lina Iyer <lina.iyer@linaro.org> wrote:
>
>> SPM is a hardware block that controls the peripheral logic surrounding
>> the application cores (cpu/l$). When the core executes WFI instruction,
>> the SPM takes over the putting the core in low power state as
>> configured. The wake up for the SPM is an interrupt at the GIC, which
>> then completes the rest of low power mode sequence and brings the core
>> out of low power mode.
>>
>> The SPM has a set of control registers that configure the SPMs
>> individually based on the type of the core and the runtime conditions.
>> SPM is a finite state machine block to which a sequence is provided and
>> it interprets the bytes and executes them in sequence. Each low power
>> mode that the core can enter into is provided to the SPM as a sequence.
>>
>> Configure the SPM to set the core (cpu or L2) into its low power mode,
>> the index of the first command in the sequence is set in the SPM_CTL
>> register. When the core executes ARM wfi instruction, it triggers the
>> SPM state machine to start executing from that index. The SPM state
>> machine waits until the interrupt occurs and starts executing the rest
>> of the sequence until it hits the end of the sequence. The end of the
>> sequence jumps the core out of its low power mode.
>>
>> Add support for an idle driver to set up the SPM to place the core in
>> Standby or Standalone power collapse mode when the core is idle.
>>
>> Based on work by: Mahesh Sivasubramanian <msivasub@codeaurora.org>,
>> Ai Li <ali@codeaurora.org>, Praveen Chidambaram <pchidamb@codeaurora.org>
>> Original tree available at -
>> git://codeaurora.org/quic/la/kernel/msm-3.10.git
>>
>> Cc: Stephen Boyd <sboyd@codeaurora.org>
>> Cc: Arnd Bergmann <arnd@arndb.de>
>> Cc: Kevin Hilman <khilman@linaro.org>
>> Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
>> Signed-off-by: Lina Iyer <lina.iyer@linaro.org>
>> ---
>> .../devicetree/bindings/arm/msm/qcom,saw2.txt      |  31 +-
>> drivers/soc/qcom/Kconfig                           |   7 +
>> drivers/soc/qcom/Makefile                          |   1 +
>> drivers/soc/qcom/spm.c                             | 422 +++++++++++++++++++++
>> 4 files changed, 455 insertions(+), 6 deletions(-)
>> create mode 100644 drivers/soc/qcom/spm.c
>>
>> diff --git a/Documentation/devicetree/bindings/arm/msm/qcom,saw2.txt b/Documentation/devicetree/bindings/arm/msm/qcom,saw2.txt
>> index 1505fb8..690c3c0 100644
>> --- a/Documentation/devicetree/bindings/arm/msm/qcom,saw2.txt
>> +++ b/Documentation/devicetree/bindings/arm/msm/qcom,saw2.txt
>> @@ -2,11 +2,20 @@ SPM AVS Wrapper 2 (SAW2)
>>
>> The SAW2 is a wrapper around the Subsystem Power Manager (SPM) and the
>> Adaptive Voltage Scaling (AVS) hardware. The SPM is a programmable
>> -micro-controller that transitions a piece of hardware (like a processor or
>> +power-controller that transitions a piece of hardware (like a processor or
>> subsystem) into and out of low power modes via a direct connection to
>> the PMIC. It can also be wired up to interact with other processors in the
>> system, notifying them when a low power state is entered or exited.
>>
>> +Multiple revisions of the SAW hardware are supported using these Device Nodes.
>> +SAW2 revisions differ in the register offset and configuration data. Also, the
>> +same revision of the SAW in different SoCs may have different configuration
>> +data due the the differences in hardware capabilities. Hence the SoC name, the
>> +version of the SAW hardware in that SoC and the distinction between cpu (big
>> +or Little) or cache, may be needed to uniquely identify the SAW register
>> +configuration and initialization data. The compatible string is used to
>> +indicate this parameter.
>> +
>> PROPERTIES
>>
>> - compatible:
>> @@ -14,10 +23,13 @@ PROPERTIES
>> 	Value type: <string>
>> 	Definition: shall contain "qcom,saw2". A more specific value should be
>> 		    one of:
>> -			 "qcom,saw2-v1"
>> -			 "qcom,saw2-v1.1"
>> -			 "qcom,saw2-v2"
>> -			 "qcom,saw2-v2.1"
>> +			"qcom,saw2-v1"
>> +			"qcom,saw2-v1.1"
>> +			"qcom,saw2-v2"
>> +			"qcom,saw2-v2.1"
>> +			"qcom,apq8064-saw2-v1.1-cpu"
>> +			"qcom,msm8974-saw2-v2.1-cpu"
>> +			"qcom,apq8084-saw2-v2.1-cpu”
>>
>
>We don’t seem to use the "qcom,saw2-v1*” variants so should we just drop them?

Sure. Will fix in the next.
>
>
>> - reg:
>> 	Usage: required
>> @@ -26,10 +38,17 @@ PROPERTIES
>> 		    the register region. An optional second element specifies
>> 		    the base address and size of the alias register region.
>>
>> +- regulator:
>> +	Usage: optional
>> +	Value type: boolean
>> +	Definition: Indicates that this SPM device acts as a regulator device
>> +			device for the core (CPU or Cache) the SPM is attached
>> +			to.
>>
>> Example:
>>
>> -	regulator@2099000 {
>> +	power-controller@2099000 {
>> 		compatible = "qcom,saw2";
>> 		reg = <0x02099000 0x1000>, <0x02009000 0x1000>;
>> +		regulator;
>> 	};
>
>- k
>
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