PM / OPP: Introduce dev_pm_opp_get_max_volt_latency()

In few use cases (like: cpufreq), it is desired to get the maximum
voltage latency for changing OPPs. Add support for that.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Reviewed-by: Stephen Boyd <sboyd@codeaurora.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

1 files changed, 59 insertions, 0 deletions

diff --git a/drivers/base/power/opp/core.c b/drivers/base/power/opp/core.c
index 71545becfca1..ffe2406af882 100644
--- a/drivers/base/power/opp/core.c
+++ b/drivers/base/power/opp/core.c
@@ -231,6 +231,65 @@ unsigned long dev_pm_opp_get_max_clock_latency(struct device *dev)
 EXPORT_SYMBOL_GPL(dev_pm_opp_get_max_clock_latency);
 
 /**
+ * dev_pm_opp_get_max_volt_latency() - Get max voltage latency in nanoseconds
+ * @dev: device for which we do this operation
+ *
+ * Return: This function returns the max voltage latency in nanoseconds.
+ *
+ * Locking: This function takes rcu_read_lock().
+ */
+unsigned long dev_pm_opp_get_max_volt_latency(struct device *dev)
+{
+        struct device_opp *dev_opp;
+        struct dev_pm_opp *opp;
+        struct regulator *reg;
+        unsigned long latency_ns = 0;
+        unsigned long min_uV = ~0, max_uV = 0;
+        int ret;
+
+        rcu_read_lock();
+
+        dev_opp = _find_device_opp(dev);
+        if (IS_ERR(dev_opp)) {
+                rcu_read_unlock();
+                return 0;
+        }
+
+        reg = dev_opp->regulator;
+        if (IS_ERR_OR_NULL(reg)) {
+                /* Regulator may not be required for device */
+                if (reg)
+                        dev_err(dev, "%s: Invalid regulator (%ld)\n", __func__,
+                                PTR_ERR(reg));
+                rcu_read_unlock();
+                return 0;
+        }
+
+        list_for_each_entry_rcu(opp, &dev_opp->opp_list, node) {
+                if (!opp->available)
+                        continue;
+
+                if (opp->u_volt_min < min_uV)
+                        min_uV = opp->u_volt_min;
+                if (opp->u_volt_max > max_uV)
+                        max_uV = opp->u_volt_max;
+        }
+
+        rcu_read_unlock();
+
+        /*
+         * The caller needs to ensure that dev_opp (and hence the regulator)
+         * isn't freed, while we are executing this routine.
+         */
+        ret = regulator_set_voltage_time(reg, min_uV, max_uV);
+        if (ret > 0)
+                latency_ns = ret * 1000;
+
+        return latency_ns;
+}
+EXPORT_SYMBOL_GPL(dev_pm_opp_get_max_volt_latency);
+
+/**
  * dev_pm_opp_get_suspend_opp() - Get suspend opp
  * @dev:        device for which we do this operation
  *