OPP: Add dev_pm_opp_{set|put}_genpd_virt_dev() helper

Multiple generic power domains for a consumer device are supported with
the help of virtual devices, which are created for each consumer device
- genpd pair. These are the device structures which are attached to the
power domain and are required by the OPP core to set the performance
state of the genpd.

The helpers added by this commit are required to be called once for each
of these virtual devices. These are required only if multiple domains
are available for a device, otherwise the actual device structure will
be used instead by the OPP core.

The new helpers also support the complex cases where the consumer device
wouldn't always require all the domains. For example, a camera may
require only one power domain during normal operations but two during
high resolution operations. The consumer driver can call
dev_pm_opp_put_genpd_virt_dev(high_resolution_genpd_virt_dev) if it is
currently operating in the normal mode and doesn't have any performance
requirements from the genpd which manages high resolution power
requirements. The consumer driver can later call
dev_pm_opp_set_genpd_virt_dev(high_resolution_genpd_virt_dev) once it
switches back to the high resolution mode.

The new helpers differ from other OPP set/put helpers as the new ones
can be called with OPPs initialized for the table as we may need to call
them on the fly because of the complex case explained above. For this
reason it is possible that the genpd virt_dev structure may be used in
parallel while the new helpers are running and a new mutex is added to
protect against that. We didn't use the existing opp_table->lock mutex
as that is widely used in the OPP core and we will need this lock in the
dev_pm_opp_set_rate() helper while changing OPP and we need to make sure
there is not much contention while doing that as that's the hotpath.

Reviewed-by: Ulf Hansson <ulf.hansson@linaro.org>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>

1 files changed, 8 insertions, 0 deletions

diff --git a/include/linux/pm_opp.h b/include/linux/pm_opp.h
index 5d399eeef172..8fed222c089b 100644
--- a/include/linux/pm_opp.h
+++ b/include/linux/pm_opp.h
@@ -126,6 +126,8 @@ struct opp_table *dev_pm_opp_set_clkname(struct device *dev, const char * name);
 void dev_pm_opp_put_clkname(struct opp_table *opp_table);
 struct opp_table *dev_pm_opp_register_set_opp_helper(struct device *dev, int (*set_opp)(struct dev_pm_set_opp_data *data));
 void dev_pm_opp_unregister_set_opp_helper(struct opp_table *opp_table);
+struct opp_table *dev_pm_opp_set_genpd_virt_dev(struct device *dev, struct device *virt_dev, int index);
+void dev_pm_opp_put_genpd_virt_dev(struct opp_table *opp_table, struct device *virt_dev);
 int dev_pm_opp_set_rate(struct device *dev, unsigned long target_freq);
 int dev_pm_opp_set_sharing_cpus(struct device *cpu_dev, const struct cpumask *cpumask);
 int dev_pm_opp_get_sharing_cpus(struct device *cpu_dev, struct cpumask *cpumask);
@@ -272,6 +274,12 @@ static inline struct opp_table *dev_pm_opp_set_clkname(struct device *dev, const
 
 static inline void dev_pm_opp_put_clkname(struct opp_table *opp_table) {}
 
+static inline struct opp_table *dev_pm_opp_set_genpd_virt_dev(struct device *dev, struct device *virt_dev, int index)
+{
+	return ERR_PTR(-ENOTSUPP);
+}
+
+static inline void dev_pm_opp_put_genpd_virt_dev(struct opp_table *opp_table, struct device *virt_dev) {}
 static inline int dev_pm_opp_set_rate(struct device *dev, unsigned long target_freq)
 {
 	return -ENOTSUPP;