[RFC v3 03/12] PM / cpu_domains: Setup PM domains for CPUs/clusters

Lina Iyer [off-list ref] writes:

Define and add Generic PM domains (genpd) for CPU clusters. Many new

Not sure this is "new". :)

SoCs group CPUs as clusters. Clusters share common resources like power
rails, caches, VFP, Coresight etc. When all CPUs in the cluster are
idle, these shared resources may also be put in their idle state.

CPUs may be associated with their domain providers in DT. The domains in
turn may be associated with their providers.

Not sure what this sentence means.

This is clean way to model
the cluster hierarchy like that of ARM's big.little architecture.

... or any multi-cluster architecture with independent power rails.

For each CPU in the DT, we identify the domain provider; initialize and
register the PM domain if isn't already registered and attach all the
CPU devices to the domain. Usually, when there are multiple clusters of
CPUs, there is a top level coherency domain that is dependent on these
individual domains. All domains thus created are marked IRQ safe
automatically and therefore may be powered down when the CPUs in the
domain are powered down by cpuidle.

s/by cpuidle/during the idle path/

A bit about why IRQ safe is needed during the idle path would be good also.

Reading DT, initializing Generic PM domains, attaching CPUs to it

s/it/their/

domains are common functionalities across ARM SoCs. Provide a common set

s/ARM/many/

of APIs to setup PM domains for CPU clusters and its parents. The
platform drivers may just call of_setup_cpu_pd() to do a single step
setup of CPU domains.

Cc: Ulf Hansson <redacted>
Cc: Daniel Lezcano <redacted>
Cc: Lorenzo Pieralisi <redacted>
Suggested-by: Kevin Hilman <redacted>
Signed-off-by: Lina Iyer <redacted>
---
 drivers/base/power/Makefile      |   1 +
 drivers/base/power/cpu_domains.c | 267 +++++++++++++++++++++++++++++++++++++++
 include/linux/cpu_domains.h      |  35 +++++

nit: cpu_pm_domains.[ch] ?

 3 files changed, 303 insertions(+)
 create mode 100644 drivers/base/power/cpu_domains.c
 create mode 100644 include/linux/cpu_domains.h

[...]

+/**
+ * of_init_cpu_pm_domain() - Initialize a CPU PM domain from a device node
+ *
+ * @dn: The domain provider's device node
+ * @ops: The power_on/_off callbacks for the domain
+ *
+ * Returns the generic_pm_domain (genpd) pointer to the domain on success
+ */
+static struct generic_pm_domain *of_init_cpu_pm_domain(struct device_node *dn,
+				const struct cpu_pd_ops *ops)
+{
+	struct cpu_pm_domain *pd = NULL;
+	struct generic_pm_domain *genpd = NULL;
+	int ret = -ENOMEM;
+
+	if (!of_device_is_available(dn))
+		return ERR_PTR(-ENODEV);
+
+	genpd = kzalloc(sizeof(*genpd), GFP_KERNEL);
+	if (!genpd)
+		goto fail;
+
+	genpd->name = kstrndup(dn->full_name, CPU_PD_NAME_MAX, GFP_KERNEL);
+	if (!genpd->name)
+		goto fail;
+
+	pd = kzalloc(sizeof(*pd), GFP_KERNEL);
+	if (!pd)
+		goto fail;
+
+	pd->genpd = genpd;
+	pd->genpd->power_off = cpu_pd_power_off;
+	pd->genpd->power_on = cpu_pd_power_on;
+	pd->genpd->flags |= GENPD_FLAG_IRQ_SAFE;

Again, just to be thorough, maybe a comment here describing that CPU PM
domains must be IRQ safe because the callbacks happend during the idle
path when interrupts are disabled.

[...]

I ran out of time for the day here, but will continue looking at the
rest implementation later.  Thought it best to send what I already
reviewed though.

Kevin