metag: init common clk and use "core" clk

If the common clock framework is enabled, call of_clk_init(NULL) in
time_init() to register device tree clocks with the clock framework.

After this time_init() calls a new function init_metag_clocks(), which
looks for a clock named "core" in the node compatible with "img,meta"
(usually the root node). If found the get_core_freq machine callback is
overridden to obtain the core clock frequency using that clock.

Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Mike Turquette <mturquette@linaro.org>
Cc: Grant Likely <grant.likely@linaro.org>
Cc: Rob Herring <rob.herring@calxeda.com>
Cc: devicetree-discuss@lists.ozlabs.org

1 files changed, 56 insertions, 1 deletions

diff --git a/arch/metag/kernel/clock.c b/arch/metag/kernel/clock.c
index defc840..8bfd6a5 100644
--- a/arch/metag/kernel/clock.c
+++ b/arch/metag/kernel/clock.c
@@ -8,8 +8,10 @@
  * published by the Free Software Foundation.
  */
 
+#include <linux/clk.h>
 #include <linux/delay.h>
 #include <linux/io.h>
+#include <linux/of.h>
 
 #include <asm/param.h>
 #include <asm/clock.h>
@@ -34,8 +36,61 @@ static unsigned long get_core_freq_default(void)
 #endif
 }
 
+static struct clk *clk_core;
+
+/* Clk based get_core_freq callback. */
+static unsigned long get_core_freq_clk(void)
+{
+	return clk_get_rate(clk_core);
+}
+
+/**
+ * init_metag_core_clock() - Set up core clock from devicetree.
+ *
+ * Checks to see if a "core" clock is provided in the device tree, and overrides
+ * the get_core_freq callback to use it.
+ */
+static void __init init_metag_core_clock(void)
+{
+	/*
+	 * See if a core clock is provided by the devicetree (and
+	 * registered by the init callback above).
+	 */
+	struct device_node *node;
+	node = of_find_compatible_node(NULL, NULL, "img,meta");
+	if (!node) {
+		pr_warn("%s: no compatible img,meta DT node found\n",
+			__func__);
+		return;
+	}
+
+	clk_core = of_clk_get_by_name(node, "core");
+	if (IS_ERR(clk_core)) {
+		pr_warn("%s: no core clock found in DT\n",
+			__func__);
+		return;
+	}
+
+	/*
+	 * Override the core frequency callback to use
+	 * this clk.
+	 */
+	_meta_clock.get_core_freq = get_core_freq_clk;
+}
+
+/**
+ * init_metag_clocks() - Set up clocks from devicetree.
+ *
+ * Set up important clocks from device tree. In particular any needed for clock
+ * sources.
+ */
+void __init init_metag_clocks(void)
+{
+	init_metag_core_clock();
+}
+
 /**
- * setup_meta_clocks() - Set up the Meta clock.
+ * setup_meta_clocks() - Early set up of the Meta clock.
  * @desc:	Clock descriptor usually provided by machine description
  *
  * Ensures all callbacks are valid.