PM / OPP: Initialize OPP table from device tree

With a lot of devices booting from device tree nowadays, it requires
that OPP table can be initialized from device tree.  The patch adds
a helper function of_init_opp_table together with a binding doc for
that purpose.

Signed-off-by: Shawn Guo <shawn.guo@linaro.org>
Acked-by: Rob Herring <rob.herring@calxeda.com>
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>

3 files changed, 80 insertions, 0 deletions

diff --git a/Documentation/devicetree/bindings/power/opp.txt b/Documentation/devicetree/bindings/power/opp.txt
new file mode 100644
index 000000000000..74499e5033fc
--- /dev/null
+++ b/Documentation/devicetree/bindings/power/opp.txt
@@ -0,0 +1,25 @@
+* Generic OPP Interface
+
+SoCs have a standard set of tuples consisting of frequency and
+voltage pairs that the device will support per voltage domain. These
+are called Operating Performance Points or OPPs.
+
+Properties:
+- operating-points: An array of 2-tuples items, and each item consists
+  of frequency and voltage like <freq-kHz vol-uV>.
+        freq: clock frequency in kHz
+        vol: voltage in microvolt
+
+Examples:
+
+cpu@0 {
+        compatible = "arm,cortex-a9";
+        reg = <0>;
+        next-level-cache = <&L2>;
+        operating-points = <
+                /* kHz    uV */
+                792000  1100000
+                396000  950000
+                198000  850000
+        >;
+};
diff --git a/drivers/base/power/opp.c b/drivers/base/power/opp.c
index ac993eafec82..d9468642fc41 100644
--- a/drivers/base/power/opp.c
+++ b/drivers/base/power/opp.c
@@ -22,6 +22,7 @@
 #include <linux/rculist.h>
 #include <linux/rcupdate.h>
 #include <linux/opp.h>
+#include <linux/of.h>
 
 /*
  * Internal data structure organization with the OPP layer library is as
@@ -674,3 +675,49 @@ struct srcu_notifier_head *opp_get_notifier(struct device *dev)
 
         return &dev_opp->head;
 }
+
+#ifdef CONFIG_OF
+/**
+ * of_init_opp_table() - Initialize opp table from device tree
+ * @dev:        device pointer used to lookup device OPPs.
+ *
+ * Register the initial OPP table with the OPP library for given device.
+ */
+int of_init_opp_table(struct device *dev)
+{
+        const struct property *prop;
+        const __be32 *val;
+        int nr;
+
+        prop = of_find_property(dev->of_node, "operating-points", NULL);
+        if (!prop)
+                return -ENODEV;
+        if (!prop->value)
+                return -ENODATA;
+
+        /*
+         * Each OPP is a set of tuples consisting of frequency and
+         * voltage like <freq-kHz vol-uV>.
+         */
+        nr = prop->length / sizeof(u32);
+        if (nr % 2) {
+                dev_err(dev, "%s: Invalid OPP list\n", __func__);
+                return -EINVAL;
+        }
+
+        val = prop->value;
+        while (nr) {
+                unsigned long freq = be32_to_cpup(val++) * 1000;
+                unsigned long volt = be32_to_cpup(val++);
+
+                if (opp_add(dev, freq, volt)) {
+                        dev_warn(dev, "%s: Failed to add OPP %ld\n",
+                                 __func__, freq);
+                        continue;
+                }
+                nr -= 2;
+        }
+
+        return 0;
+}
+#endif
diff --git a/include/linux/opp.h b/include/linux/opp.h
index 2a4e5faee904..214e0ebcb84d 100644
--- a/include/linux/opp.h
+++ b/include/linux/opp.h
@@ -48,6 +48,14 @@ int opp_disable(struct device *dev, unsigned long freq);
 
 struct srcu_notifier_head *opp_get_notifier(struct device *dev);
 
+#ifdef CONFIG_OF
+int of_init_opp_table(struct device *dev);
+#else
+static inline int of_init_opp_table(struct device *dev)
+{
+        return -EINVAL;
+}
+#endif /* CONFIG_OF */
 #else
 static inline unsigned long opp_get_voltage(struct opp *opp)
 {