clk: Support for clock parents and rates assigned from device tree

This patch adds helper functions to configure clock parents and rates
as specified through 'assigned-clock-parents', 'assigned-clock-rates'
DT properties for a clock provider or clock consumer device.
The helpers are now being called by the bus code for the platform, I2C
and SPI busses, before the driver probing and also in the clock core
after registration of a clock provider.

Change-Id: I96d98c9c9d576fcbf0dfc90d1cc75feb9fdf97cb
Signed-off-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
[s.nawrocki@samsung.com: backported to v3.10]
Acked-by: Kyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: Mike Turquette <mturquette@linaro.org>

3 files changed, 154 insertions, 1 deletions

diff --git a/drivers/clk/Makefile b/drivers/clk/Makefile
index bfe0cb6988a..9d805618753 100644
--- a/drivers/clk/Makefile
+++ b/drivers/clk/Makefile
@@ -8,6 +8,9 @@ obj-$(CONFIG_COMMON_CLK)	+= clk-fixed-rate.o
 obj-$(CONFIG_COMMON_CLK)	+= clk-gate.o
 obj-$(CONFIG_COMMON_CLK)	+= clk-mux.o
 obj-$(CONFIG_COMMON_CLK)	+= clk-composite.o
+ifeq ($(CONFIG_OF), y)
+obj-$(CONFIG_COMMON_CLK)	+= clk-conf.o
+endif
 
 # SoCs specific
 obj-$(CONFIG_ARCH_BCM2835)	+= clk-bcm2835.o
diff --git a/drivers/clk/clk-conf.c b/drivers/clk/clk-conf.c
new file mode 100644
index 00000000000..1f73019a27c
--- /dev/null
+++ b/drivers/clk/clk-conf.c
@@ -0,0 +1,143 @@
+/*
+ * Copyright (C) 2014 Samsung Electronics Co., Ltd.
+ * Sylwester Nawrocki <s.nawrocki@samsung.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include <linux/clk.h>
+#include <linux/clk-provider.h>
+#include <linux/clk/clk-conf.h>
+#include <linux/device.h>
+#include <linux/of.h>
+#include <linux/printk.h>
+#include "clk.h"
+
+static int __set_clk_parents(struct device_node *node, bool clk_supplier)
+{
+	struct of_phandle_args clkspec;
+	int index, rc, num_parents;
+	struct clk *clk, *pclk;
+
+	num_parents = of_count_phandle_with_args(node, "assigned-clock-parents",
+						 "#clock-cells");
+	if (num_parents == -EINVAL)
+		pr_err("clk: invalid value of clock-parents property at %s\n",
+		       node->full_name);
+
+	for (index = 0; index < num_parents; index++) {
+		rc = of_parse_phandle_with_args(node, "assigned-clock-parents",
+					"#clock-cells",	index, &clkspec);
+		if (rc < 0) {
+			/* skip empty (null) phandles */
+			if (rc == -ENOENT)
+				continue;
+			else
+				return rc;
+		}
+		if (clkspec.np == node && !clk_supplier)
+			return 0;
+		pclk = of_clk_get_by_clkspec(&clkspec);
+		if (IS_ERR(pclk)) {
+			pr_warn("clk: couldn't get parent clock %d for %s\n",
+				index, node->full_name);
+			return PTR_ERR(pclk);
+		}
+
+		rc = of_parse_phandle_with_args(node, "assigned-clocks",
+					"#clock-cells", index, &clkspec);
+		if (rc < 0)
+			goto err;
+		if (clkspec.np == node && !clk_supplier) {
+			rc = 0;
+			goto err;
+		}
+		clk = of_clk_get_by_clkspec(&clkspec);
+		if (IS_ERR(pclk)) {
+			pr_warn("clk: couldn't get parent clock %d for %s\n",
+				index, node->full_name);
+			rc = PTR_ERR(pclk);
+			goto err;
+		}
+
+		rc = clk_set_parent(clk, pclk);
+		if (rc < 0)
+			pr_err("clk: failed to reparent %s to %s: %d\n",
+			       __clk_get_name(clk), __clk_get_name(pclk), rc);
+		clk_put(clk);
+		clk_put(pclk);
+	}
+	return 0;
+err:
+	clk_put(pclk);
+	return rc;
+}
+
+static int __set_clk_rates(struct device_node *node, bool clk_supplier)
+{
+	struct of_phandle_args clkspec;
+	struct property	*prop;
+	const __be32 *cur;
+	int rc, index = 0;
+	struct clk *clk;
+	u32 rate;
+
+	of_property_for_each_u32(node, "assigned-clock-rates", prop, cur, rate) {
+		if (rate) {
+			rc = of_parse_phandle_with_args(node, "assigned-clocks",
+					"#clock-cells",	index, &clkspec);
+			if (rc < 0) {
+				/* skip empty (null) phandles */
+				if (rc == -ENOENT)
+					continue;
+				else
+					return rc;
+			}
+			if (clkspec.np == node && !clk_supplier)
+				return 0;
+
+			clk = of_clk_get_by_clkspec(&clkspec);
+			if (IS_ERR(clk)) {
+				pr_warn("clk: couldn't get clock %d for %s\n",
+					index, node->full_name);
+				return PTR_ERR(clk);
+			}
+
+			rc = clk_set_rate(clk, rate);
+			if (rc < 0)
+				pr_err("clk: couldn't set %s clock rate: %d\n",
+				       __clk_get_name(clk), rc);
+			clk_put(clk);
+		}
+		index++;
+	}
+	return 0;
+}
+
+/**
+ * of_clk_set_defaults() - parse and set assigned clocks configuration
+ * @node: device node to apply clock settings for
+ * @clk_supplier: true if clocks supplied by @node should also be considered
+ *
+ * This function parses 'assigned-{clocks/clock-parents/clock-rates}' properties
+ * and sets any specified clock parents and rates. The @clk_supplier argument
+ * should be set to true if @node may be also a clock supplier of any clock
+ * listed in its 'assigned-clocks' or 'assigned-clock-parents' properties.
+ * If @clk_supplier is false the function exits returnning 0 as soon as it
+ * determines the @node is also a supplier of any of the clocks.
+ */
+int of_clk_set_defaults(struct device_node *node, bool clk_supplier)
+{
+	int rc;
+
+	if (!node)
+		return 0;
+
+	rc = __set_clk_parents(node, clk_supplier);
+	if (rc < 0)
+		return rc;
+
+	return __set_clk_rates(node, clk_supplier);
+}
diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
index ba2f31b1861..2b5b7155bb0 100644
--- a/drivers/clk/clk.c
+++ b/drivers/clk/clk.c
@@ -10,6 +10,7 @@
  */
 
 #include <linux/clk-private.h>
+#include <linux/clk/clk-conf.h>
 #include <linux/module.h>
 #include <linux/mutex.h>
 #include <linux/spinlock.h>
@@ -2191,6 +2192,7 @@ int of_clk_add_provider(struct device_node *np,
 			void *data)
 {
 	struct of_clk_provider *cp;
+	int ret;
 
 	cp = kzalloc(sizeof(struct of_clk_provider), GFP_KERNEL);
 	if (!cp)
@@ -2205,7 +2207,11 @@ int of_clk_add_provider(struct device_node *np,
 	mutex_unlock(&of_clk_mutex);
 	pr_debug("Added clock from %s\n", np->full_name);
 
-	return 0;
+	ret = of_clk_set_defaults(np, true);
+	if (ret < 0)
+		of_clk_del_provider(np);
+
+	return ret;
 }
 EXPORT_SYMBOL_GPL(of_clk_add_provider);
 
@@ -2299,6 +2305,7 @@ void __init of_clk_init(const struct of_device_id *matches)
 		const struct of_device_id *match = of_match_node(matches, np);
 		of_clk_init_cb_t clk_init_cb = match->data;
 		clk_init_cb(np);
+		of_clk_set_defaults(np, true);
 	}
 }
 #endif