On Sep 23, 2014, at 6:51 PM, Lina Iyer <lina.iyer@xxxxxxxxxx> wrote:
> 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@xxxxxxxxxx>
> [lina: simplify the driver for initial submission, clean up and update
> commit text]
> ---
> Documentation/devicetree/bindings/arm/msm/spm.txt | 43 +++
> drivers/soc/qcom/Kconfig | 8 +
> drivers/soc/qcom/Makefile | 1 +
> drivers/soc/qcom/spm.c | 388 ++++++++++++++++++++++
> include/soc/qcom/spm.h | 38 +++
> 5 files changed, 478 insertions(+)
> create mode 100644 Documentation/devicetree/bindings/arm/msm/spm.txt
> create mode 100644 drivers/soc/qcom/spm.c
> create mode 100644 include/soc/qcom/spm.h
>
> diff --git a/Documentation/devicetree/bindings/arm/msm/spm.txt b/Documentation/devicetree/bindings/arm/msm/spm.txt
> new file mode 100644
> index 0000000..2ff2454
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/arm/msm/spm.txt
> @@ -0,0 +1,43 @@
> +* Subsystem Power Manager (SPM)
> +
> +Qualcomm Snapdragons have SPM hardware blocks to control the Application
> +Processor Sub-System power. These SPM blocks run individual state machine
> +to determine what the core (L2 or Krait/Scorpion) would do when the WFI
> +instruction is executed by the core.
> +
> +The devicetree representation of the SPM block should be:
> +
> +Required properties
> +
> +- compatible: Must be -
> + "qcom,spm-v2.1"
> +- reg: The physical address and the size of the SPM's memory mapped registers
> +- qcom,cpu: phandle for the CPU that the SPM block is attached to.
> + This field is required on only for SPMs that control the CPU.
Let’s make this just cpu-handle instead of qcom,cpu. The concept of a handle to a cpu is pretty generic.
> +- qcom,saw2-clk-div: SAW2 configuration register to program the SPM runtime
> + clocks. The register for this property is MSM_SPM_REG_SAW2_CFG.
(add details on how this is used to compute timer tick. Is it timer tick = saw_clk/saw2-clk-div? What is valid range of values)
> +- qcom,saw2-delays: The SPM delay values that SPM sequences would refer to.
> + The register for this property is MSM_SPM_REG_SAW2_SPM_DLY.
Didn’t Stephen asked about splitting this up? Or at least treating it as an array of 3 values?
> +- qcom,saw2-enable: The SPM control register to enable/disable the sleep state
> + machine. The register for this property is MSM_SPM_REG_SAW2_SPM_CTL.
Can this just be a boolean (exist or not), if so, probably change it to qcom,saw2-disable (so lack of property means enable)?
> +
> +Optional properties
> +
> +- qcom,saw2-spm-cmd-wfi: The WFI command sequence
probably add something like: “array of bytes …” (want to convey the data type somehow, is there a max length?)
> +- qcom,saw2-spm-cmd-spc: The Standalone PC command sequence
probably add something like: “array of bytes …” (want to convey the data type somehow, is there a max length?)
> +
> +Example:
> + spm@f9089000 {
> + compatible = "qcom,spm-v2.1";
> + #address-cells = <1>;
> + #size-cells = <1>;
> + reg = <0xf9089000 0x1000>;
> + qcom,cpu = <&CPU0>;
> + qcom,saw2-clk-div = <0x1>;
> + qcom,saw2-delays = <0x20000400>;
> + qcom,saw2-enable = <0x1>;
> + qcom,saw2-spm-cmd-wfi = [03 0b 0f];
> + qcom,saw2-spm-cmd-spc = [00 20 50 80 60 70 10 92
> + a0 b0 03 68 70 3b 92 a0 b0
> + 82 2b 50 10 30 02 22 30 0f];
> + };
- k
--
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