[RFC PATCH 1/2] PM: domains: Allow devices attached to genpd to be managed by HW

Abel Vesa
2023-06-27T10:40:50Z

From: Ulf Hansson <ulf.hansson@linaro.org>

Some power-domains may be capable of relying on the HW to control the power
for a device that's hooked up to it. Typically, for these kinds of
configurations the device doesn't really need to be attached to a PM domain
(genpd), from Linux point of view. However, in some cases the behaviour of
the power-domain and its device can be changed in runtime.

To allow a consumer driver to change the behaviour of the PM domain for its
device, let's provide a new function, dev_pm_genpd_set_hwmode(). Moreover,
let's add a corresponding optional genpd callback, ->set_hwmode_dev(),
which the genpd provider should implement if it can support switching
between HW controlled mode and SW controlled mode.

Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
---
drivers/base/power/domain.c | 66 +++++++++++++++++++++++++++++++++++++
include/linux/pm_domain.h | 15 +++++++++
2 files changed, 81 insertions(+)

diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c
index 5cb2023581d4..23286853d1d0 100644
--- a/drivers/base/power/domain.c
+++ b/drivers/base/power/domain.c
@@ -541,6 +541,72 @@ void dev_pm_genpd_synced_poweroff(struct device *dev)
}
EXPORT_SYMBOL_GPL(dev_pm_genpd_synced_poweroff);

+/**
+ * dev_pm_genpd_set_hwmode - Set the HW mode for the device and its PM domain.
+ *
+ * @dev: Device for which the HW-mode should be changed.
+ * @enable: Value to set or unset the HW-mode.
+ *
+ * Some PM domains can rely on HW signals to control the power for a device. To
+ * allow a consumer driver to switch the behaviour for its device in runtime,
+ * which may be beneficial from a latency or energy point of view, this function
+ * may be called.
+ *
+ * It is assumed that the users guarantee that the genpd wouldn't be detached
+ * while this routine is getting called.
+ *
+ * Returns 0 on success and negative error values on failures.
+ */
+int dev_pm_genpd_set_hwmode(struct device *dev, bool enable)
+{
+ struct generic_pm_domain *genpd;
+ int ret = 0;
+
+ genpd = dev_to_genpd_safe(dev);
+ if (!genpd)
+ return -ENODEV;
+
+ if (!genpd->set_hwmode_dev)
+ return -EOPNOTSUPP;
+
+ genpd_lock(genpd);
+
+ if (dev_gpd_data(dev)->hw_mode == enable)
+ goto out;
+
+ ret = genpd->set_hwmode_dev(genpd, dev, enable);
+ if (!ret)
+ dev_gpd_data(dev)->hw_mode = enable;
+
+out:
+ genpd_unlock(genpd);
+ return ret;
+}
+EXPORT_SYMBOL_GPL(dev_pm_genpd_set_hwmode);
+
+/**
+ * dev_pm_genpd_get_hwmode - Get the HW mode setting for the device.
+ *
+ * @dev: Device for which the current HW-mode setting should be fetched.
+ *
+ * This helper function allows consumer drivers to fetch the current HW mode
+ * setting of its the device.
+ *
+ * It is assumed that the users guarantee that the genpd wouldn't be detached
+ * while this routine is getting called.
+ */
+bool dev_pm_genpd_get_hwmode(struct device *dev)
+{
+ struct generic_pm_domain *genpd;
+
+ genpd = dev_to_genpd_safe(dev);
+ if (!genpd)
+ return false;
+
+ return dev_gpd_data(dev)->hw_mode;
+}
+EXPORT_SYMBOL_GPL(dev_pm_genpd_get_hwmode);
+
static int _genpd_power_on(struct generic_pm_domain *genpd, bool timed)
{
unsigned int state_idx = genpd->state_idx;
diff --git a/include/linux/pm_domain.h b/include/linux/pm_domain.h
index f776fb93eaa0..8f60c36851d5 100644
--- a/include/linux/pm_domain.h
+++ b/include/linux/pm_domain.h
@@ -146,6 +146,8 @@ struct generic_pm_domain {
int (*set_performance_state)(struct generic_pm_domain *genpd,
unsigned int state);
struct gpd_dev_ops dev_ops;
+ int (*set_hwmode_dev)(struct generic_pm_domain *domain,
+ struct device *dev, bool enable);
int (*attach_dev)(struct generic_pm_domain *domain,
struct device *dev);
void (*detach_dev)(struct generic_pm_domain *domain,
@@ -208,6 +210,7 @@ struct generic_pm_domain_data {
unsigned int performance_state;
unsigned int default_pstate;
unsigned int rpm_pstate;
+ bool hw_mode;
void *data;
};

@@ -237,6 +240,8 @@ int dev_pm_genpd_remove_notifier(struct device *dev);
void dev_pm_genpd_set_next_wakeup(struct device *dev, ktime_t next);
ktime_t dev_pm_genpd_get_next_hrtimer(struct device *dev);
void dev_pm_genpd_synced_poweroff(struct device *dev);
+int dev_pm_genpd_set_hwmode(struct device *dev, bool enable);
+bool dev_pm_genpd_get_hwmode(struct device *dev);

extern struct dev_power_governor simple_qos_governor;
extern struct dev_power_governor pm_domain_always_on_gov;
@@ -305,6 +310,16 @@ static inline ktime_t dev_pm_genpd_get_next_hrtimer(struct device *dev)
static inline void dev_pm_genpd_synced_poweroff(struct device *dev)
{ }

+static inline int dev_pm_genpd_set_hwmode(struct device *dev, bool enable)
+{
+ return -EOPNOTSUPP;
+}
+
+static inline bool dev_pm_genpd_get_hwmode(struct device *dev)
+{
+ return false;
+}
+
#define simple_qos_governor (*(struct dev_power_governor *)(NULL))
#define pm_domain_always_on_gov (*(struct dev_power_governor *)(NULL))
#endif
--
2.34.1