[PATCH RFC 2/3] clk: cpufreq helper for voltage scaling

[Mike Turquette]

This patch builds on "clk: notifier handler for dynamic voltage scaling"
by adding a CPUfreq-specific helper function for registering a clock
rate-change notifier to scale regulator voltage as a function of clock
rate.

In particular this patch creates an instance of struct
cpufreq_frequency_table and also calculate the voltage scaling latency,
both of which are returned to the caller for use in the CPUfreq driver.

Signed-off-by: Mike Turquette <mturquette@xxxxxxxxxx>
---
 drivers/clk/clk-voltage-notifier.c | 71 ++++++++++++++++++++++++++++++++++++++
 include/linux/clk.h                |  6 ++++
 2 files changed, 77 insertions(+)

diff --git a/drivers/clk/clk-voltage-notifier.c b/drivers/clk/clk-voltage-notifier.c
index cb6b85f..8e1707f 100644
--- a/drivers/clk/clk-voltage-notifier.c
+++ b/drivers/clk/clk-voltage-notifier.c
@@ -10,6 +10,7 @@
  */
 
 #include <linux/clk.h>
+#include <linux/cpufreq.h>
 #include <linux/device.h>
 #include <linux/module.h>
 #include <linux/notifier.h>
@@ -133,3 +134,73 @@ void of_clk_volt_notifier_unregister(struct notifier_block *nb)
 	kfree(vsd);
 }
 EXPORT_SYMBOL_GPL(of_clk_volt_notifier_unregister);
+
+void of_clk_cpufreq_notifier_unregister(struct notifier_block *nb,
+		struct cpufreq_frequency_table *freq_table)
+{
+	struct volt_scale_data *data = to_volt_scale_data(nb);
+	struct device *dev = data->dev;
+
+	opp_free_cpufreq_table(dev, &freq_table);
+	of_clk_volt_notifier_unregister(nb);
+}
+EXPORT_SYMBOL_GPL(of_clk_cpufreq_notifier_unregister);
+
+/**
+ * of_clk_cpufreq_notifer_register - register clock notifier to scale voltage
+ * @dev: device that owns this scaling operation
+ * @np: pointer to device's DT node
+ * @clk: clock whose rate-change notifier triggers voltage scaling
+ * @supply: regulator id string
+ * @freq_table: pointer to uninitialized CPUfreq frequency scaling table
+ * @voltage_latency: worst case voltage scaling latency
+ */
+struct notifier_block *of_clk_cpufreq_notifier_register(struct device *dev,
+		struct device_node *np, struct clk *clk, const char *supply,
+		struct cpufreq_frequency_table **table,
+		unsigned int *voltage_latency)
+{
+	struct notifier_block *nb;
+	struct volt_scale_data *vsd;
+	struct opp *opp;
+	unsigned long min, max;
+	int ret, i;
+
+	nb = of_clk_volt_notifier_register(dev, np, clk, supply,
+			voltage_latency);
+	if (IS_ERR(nb))
+		return nb;
+
+	vsd = to_volt_scale_data(nb);
+
+	ret = opp_init_cpufreq_table(dev, table);
+	if (ret) {
+		pr_err("failed to init cpufreq table: %d\n", ret);
+		goto err_unregister;
+	}
+
+	/* find the min and max voltages and compute worst-case latency */
+	for (i = 0; table[0][i].frequency != CPUFREQ_TABLE_END; i++)
+		;
+
+	rcu_read_lock();
+	opp = opp_find_freq_exact(dev,
+			table[0][0].frequency * 1000, true);
+	min = opp_get_voltage(opp);
+	opp = opp_find_freq_exact(dev,
+			table[0][i-1].frequency * 1000, true);
+	max = opp_get_voltage(opp);
+	rcu_read_unlock();
+
+	*voltage_latency = regulator_set_voltage_time(vsd->reg, min, max);
+	if (*voltage_latency < 0)
+		pr_warn("%s: failed to calculate voltage latency, %d\n",
+				__func__, ret);
+
+	return nb;
+
+err_unregister:
+	of_clk_volt_notifier_unregister(nb);
+	return ERR_PTR(ret);
+}
+EXPORT_SYMBOL_GPL(of_clk_cpufreq_notifier_register);
diff --git a/include/linux/clk.h b/include/linux/clk.h
index 85ea520..3104883 100644
--- a/include/linux/clk.h
+++ b/include/linux/clk.h
@@ -86,6 +86,12 @@ struct notifier_block *of_clk_volt_notifier_register(struct device *dev,
 		struct device_node *np, struct clk *clk, const char *supply,
 		int *voltage_latency);
 void of_clk_volt_notifier_unregister(struct notifier_block *nb);
+struct notifier_block *of_clk_cpufreq_notifier_register(struct device *dev,
+		struct device_node *np, struct clk *clk, const char *supply,
+		struct cpufreq_frequency_table **table,
+		unsigned int *voltage_latency);
+void of_clk_cpufreq_notifier_unregister(struct notifier_block *nb,
+		struct cpufreq_frequency_table *freq_table);
 
 #endif
 
-- 
1.8.1.2

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