Re: [PATCH v6 1/2] PM / Domains: Add support for 'required-opps' to set default perf state

Some devices within power domains with performance states do not
support DVFS, but still need to vote on a default/static state
while they are active. They can express this using the 'required-opps'
property in device tree, which points to the phandle of the OPP
supported by the corresponding power-domains.

Add support to parse this information from DT and then set the
specified performance state during attach and drop it on detach.
runtime suspend/resume callbacks already have logic to drop/set
the vote as needed and should take care of dropping the default
perf state vote on runtime suspend and restore it back on runtime
resume.

Signed-off-by: Rajendra Nayak <redacted>
---
 drivers/base/power/domain.c | 28 ++++++++++++++++++++++++++--
 include/linux/pm_domain.h   |  1 +
 2 files changed, 27 insertions(+), 2 deletions(-)

diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c
index a934c67..b9b5a9b 100644
--- a/drivers/base/power/domain.c
+++ b/drivers/base/power/domain.c

@@ -2598,6 +2598,12 @@ static void genpd_dev_pm_detach(struct device *dev, bool power_off)

        dev_dbg(dev, "removing from PM domain %s\n", pd->name);

+       /* Drop the default performance state */
+       if (dev_gpd_data(dev)->default_pstate) {
+               dev_pm_genpd_set_performance_state(dev, 0);
+               dev_gpd_data(dev)->default_pstate = 0;
+       }
+
        for (i = 1; i < GENPD_RETRY_MAX_MS; i <<= 1) {
                ret = genpd_remove_device(pd, dev);
                if (ret != -EAGAIN)

@@ -2637,6 +2643,8 @@ static int __genpd_dev_pm_attach(struct device *dev, struct device *base_dev,
 {
        struct of_phandle_args pd_args;
        struct generic_pm_domain *pd;
+       struct device_node *np;
+       int pstate;
        int ret;

        ret = of_parse_phandle_with_args(dev->of_node, "power-domains",

@@ -2675,10 +2683,26 @@ static int __genpd_dev_pm_attach(struct device *dev, struct device *base_dev,
                genpd_unlock(pd);
        }

-       if (ret)
+       if (ret) {
                genpd_remove_device(pd, dev);
+               return -EPROBE_DEFER;
+       }
+
+       /* Set the default performance state */
+       np = dev->of_node;
+       if (of_parse_phandle(np, "required-opps", index)) {

+               pstate = of_get_required_opp_performance_state(np, index);
+               if (pstate < 0) {
+                       ret = pstate;
+                       dev_err(dev, "failed to set required performance state for power-domain %s: %d\n",
+                               pd->name, ret);
+               } else {
+                       dev_pm_genpd_set_performance_state(dev, pstate);
+                       dev_gpd_data(dev)->default_pstate = pstate;
+               }
+       }

-       return ret ? -EPROBE_DEFER : 1;
+       return ret ? ret : 1;
 }

 /**

diff --git a/include/linux/pm_domain.h b/include/linux/pm_domain.h
index 21a0577..67017c9 100644
--- a/include/linux/pm_domain.h
+++ b/include/linux/pm_domain.h

@@ -198,6 +198,7 @@ struct generic_pm_domain_data {
        struct notifier_block *power_nb;
        int cpu;
        unsigned int performance_state;
+       unsigned int default_pstate;
        unsigned int rpm_pstate;
        ktime_t next_wakeup;
        void *data;