clk: provide prepare/unprepare functions
As discussed previously, there's the need on some platforms to run some
parts of clk_enable() in contexts which can schedule. The solution
which was agreed upon was to provide clk_prepare() and clk_unprepare()
to contain this parts, while clk_enable() and clk_disable() perform
the atomic part.
This patch provides a common definition for clk_prepare() and
clk_unprepare() in linux/clk.h, and provides an upgrade path for
existing implementation and drivers: drivers can start using
clk_prepare() and clk_unprepare() once this patch is merged without
having to wait for platform support. Platforms can then start to
provide these additional functions.
Eventually, HAVE_CLK_PREPARE will be removed from the kernel, and
everyone will have to provide these new APIs.
Change-Id: Ib9d24a7a0fdb571d392b970b1c159acabb07b365
Acked-by: Saravana Kannan <skannan@codeaurora.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
diff --git a/include/linux/clk.h b/include/linux/clk.h
index 1d37f42..7213b52 100644
--- a/include/linux/clk.h
+++ b/include/linux/clk.h
@@ -11,6 +11,8 @@
#ifndef __LINUX_CLK_H
#define __LINUX_CLK_H
+#include <linux/kernel.h>
+
struct device;
/*
@@ -41,11 +43,31 @@
struct clk *clk_get(struct device *dev, const char *id);
/**
+ * clk_prepare - prepare a clock source
+ * @clk: clock source
+ *
+ * This prepares the clock source for use.
+ *
+ * Must not be called from within atomic context.
+ */
+#ifdef CONFIG_HAVE_CLK_PREPARE
+int clk_prepare(struct clk *clk);
+#else
+static inline int clk_prepare(struct clk *clk)
+{
+ might_sleep();
+ return 0;
+}
+#endif
+
+/**
* clk_enable - inform the system when the clock source should be running.
* @clk: clock source
*
* If the clock can not be enabled/disabled, this should return success.
*
+ * May be called from atomic contexts.
+ *
* Returns success (0) or negative errno.
*/
int clk_enable(struct clk *clk);
@@ -57,6 +79,8 @@
* Inform the system that a clock source is no longer required by
* a driver and may be shut down.
*
+ * May be called from atomic contexts.
+ *
* Implementation detail: if the clock source is shared between
* multiple drivers, clk_enable() calls must be balanced by the
* same number of clk_disable() calls for the clock source to be
@@ -64,6 +88,25 @@
*/
void clk_disable(struct clk *clk);
+
+/**
+ * clk_unprepare - undo preparation of a clock source
+ * @clk: clock source
+ *
+ * This undoes a previously prepared clock. The caller must balance
+ * the number of prepare and unprepare calls.
+ *
+ * Must not be called from within atomic context.
+ */
+#ifdef CONFIG_HAVE_CLK_PREPARE
+void clk_unprepare(struct clk *clk);
+#else
+static inline void clk_unprepare(struct clk *clk)
+{
+ might_sleep();
+}
+#endif
+
/**
* clk_get_rate - obtain the current clock rate (in Hz) for a clock source.
* This is only valid once the clock source has been enabled.