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@xxxxxxxxxxxxxx>,
Ai Li <ali@xxxxxxxxxxxxxx>, Praveen Chidambaram <pchidamb@xxxxxxxxxxxxxx>
Original tree available at -
git://codeaurora.org/quic/la/kernel/msm-3.10.git
Signed-off-by: Lina Iyer <lina.iyer@xxxxxxxxxx>
---
.../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
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