[PATCH v2 2/4] PM / OPP: Initialize OPP table from device tree

[Shawn Guo]

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 at linaro.org>
---
 Documentation/devicetree/bindings/power/opp.txt |   25 +++++++++
 drivers/base/power/opp.c                        |   65 +++++++++++++++++++++++
 include/linux/opp.h                             |    8 +++
 3 files changed, 98 insertions(+), 0 deletions(-)
 create mode 100644 Documentation/devicetree/bindings/power/opp.txt

diff --git a/Documentation/devicetree/bindings/power/opp.txt b/Documentation/devicetree/bindings/power/opp.txt
new file mode 100644
index 0000000..2238520
--- /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 3-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 at 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 ac993ea..1bf1be8 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 +675,67 @@ 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)
+{
+	struct device_node *np = dev->of_node;
+	const char *propname = "operating-points";
+	const struct property *pp;
+	u32 *opp;
+	int ret, i, nr;
+
+	pp = of_find_property(np, propname, NULL);
+	if (!pp) {
+		dev_err(dev, "%s: Unable to find property", __func__);
+		return -ENODEV;
+	}
+
+	opp = kzalloc(pp->length, GFP_KERNEL);
+	if (!opp) {
+		dev_err(dev, "%s: Unable to allocate array\n", __func__);
+		return -ENOMEM;
+	}
+
+	nr = pp->length / sizeof(u32);
+	ret = of_property_read_u32_array(np, propname, opp, nr);
+	if (ret) {
+		dev_err(dev, "%s: Unable to read OPPs\n", __func__);
+		goto out;
+	}
+
+	if (nr % 2) {
+		dev_err(dev, "%s: Invalid OPP list\n", __func__);
+		ret = -EINVAL;
+		goto out;
+	}
+
+	nr /= 2;
+	for (i = 0; i < nr; i++) {
+		/*
+		 * Each OPP is a set of tuples consisting of frequency and
+		 * voltage like <freq-kHz vol-uV>.
+		 */
+		u32 *val = opp + i * 2;
+
+		val[0] *= 1000;
+		ret = opp_add(dev, val[0], val[1]);
+		if (ret) {
+			dev_warn(dev, "%s: Failed to add OPP %d: %d\n",
+				 __func__, val[0], ret);
+			continue;
+		}
+	}
+
+	ret = 0;
+out:
+	kfree(opp);
+	return ret;
+}
+#endif
diff --git a/include/linux/opp.h b/include/linux/opp.h
index 2a4e5fa..214e0eb 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)
 {
-- 
1.7.5.4