Re: [PATCH v8 1/7] qcom: spm: Add Subsystem Power Manager driver

[Sudeep Holla <sudeep.holla-5wv7dgnIgG8@public.gmane.org>]

On 07/10/14 22:41, Lina Iyer 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.
>
> Based on work by: Mahesh Sivasubramanian <msivasub-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.org>,
> Ai Li <ali-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.org>, Praveen Chidambaram <pchidamb-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.org>
> Original tree available at -
> git://codeaurora.org/quic/la/kernel/msm-3.10.git
>
> Signed-off-by: Lina Iyer <lina.iyer-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>
> ---
>   .../devicetree/bindings/arm/msm/qcom,saw2.txt      |  31 ++-
>   drivers/soc/qcom/Kconfig                           |   8 +
>   drivers/soc/qcom/Makefile                          |   1 +
>   drivers/soc/qcom/spm.c                             | 223 +++++++++++++++++++++
>   4 files changed, 257 insertions(+), 6 deletions(-)
>   create mode 100644 drivers/soc/qcom/spm.c
>

[...]

> +
> +static struct spm_driver_data *spm_get_drv(struct platform_device *pdev)
> +{
> +       struct spm_driver_data *drv = NULL;
> +       struct device_node *cpu_node, *saw_node;
> +       u32 cpu;
> +
> +       for_each_possible_cpu(cpu) {
> +               if (drv)
> +                       break;
> +               cpu_node = of_get_cpu_node(cpu, NULL);

I have not looked at the patch in detail, just this caught my attention
as I removed most of these unnecessary parsing in ARM code. Unless you
need this before topology_init, you need not parse DT to get cpu_node.
You can use of_cpu_device_node_get instead.

Regards,
Sudeep

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