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

Lina Iyer
2014-10-09T17:12:16Z

On Thu, Oct 09 2014 at 10:53 -0600, Sudeep Holla wrote:
>
>
>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@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
>>
>>Signed-off-by: Lina Iyer <lina.iyer@linaro.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.
Thanks. But in this usecase, I may need to iterate through all possible
cpus and do a get of the cpu and then get the SAW instance from that and
compare against the SPM instance that is being probed.
SPM does not have a reference to the CPU.
>
>Regards,
>Sudeep
>