Re: [PATCH v7 1/7] qcom: spm: Add Subsystem Power Manager driver

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

On Tue, Sep 30 2014 at 11:26 -0600, Kevin Hilman wrote:
>Lina Iyer <lina.iyer@linaro.org> writes:
>
>> Based on work by many authors, available at codeaurora.org
>>
>> 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.
>>
>> Signed-off-by: Lina Iyer <lina.iyer@linaro.org>
>
>[...]
>
>> diff --git a/Documentation/devicetree/bindings/arm/msm/qcom,saw2.txt b/Documentation/devicetree/bindings/arm/msm/qcom,saw2.txt
>> index 1505fb8..9a9cc99 100644
>> --- a/Documentation/devicetree/bindings/arm/msm/qcom,saw2.txt
>> +++ b/Documentation/devicetree/bindings/arm/msm/qcom,saw2.txt
>> @@ -14,10 +14,9 @@ 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,apq8064-saw2-v1.1-cpu"
>> +			 "qcom,msm8974-saw2-v2.1-cpu"
>> +			 "qcom,apq8084-saw2-v2.1-cpu"
>
>This looks odd (to me.)  Why are the SoC name and the SAW2 version both
>needed?
Even with the same version of SAW2, each SoC would have different
values for the register information like the delays, sequences etc.
The capabilities of the SoC dictate many of these values.
So in mapping the .compatible with a corresponding .data in the match
table, the cpu and the SAW version combination is necessary to identify
the set of register values.