Message-Id: <1278902245.965824.935546870026.1.gpush@pororo>
Date:	Mon, 12 Jul 2010 10:37:25 +0800
From:	Jeremy Kerr <jeremy.kerr@...onical.com>
To:	linux-arm-kernel@...ts.infradead.org
Cc:	linux-kernel@...r.kernel.org,
	Ben Herrenchmidt <benh@...nel.crashing.org>
Subject: [PATCH 1/2] Add a common struct clk

We currently have 21 definitions of struct clk in the ARM architecture,
each defined on a per-platform basis. This makes it difficult to define
platform- (or architecture-) independent clock sources without making
assumptions about struct clk, and impossible to compile two
platforms with different struct clks into a single image.

This change is an effort to unify struct clk where possible, by defining
a common struct clk, containing a set of clock operations. Different
clock implementations can set their own operations, and have a standard
interface for generic code. The callback interface is exposed to the
kernel proper, while the clock implementations only need to be seen by
the platform internals.

This allows us to share clock code among platforms, and makes it
possible to dynamically create clock devices in platform-independent
code.

Platforms can enable the generic struct clock through
CONFIG_USE_COMMON_STRUCT_CLK. In this case, the clock infrastructure
consists of a common struct clk:

struct clk {
	const struct clk_ops	*ops;
	unsigned int		enable_count;
	struct mutex		mutex;
};

And a set of clock operations (defined per type of clock):

struct clk_ops {
       int             (*enable)(struct clk *);
       void            (*disable)(struct clk *);
       unsigned long   (*get_rate)(struct clk *);
       [...]
};

To define a hardware-specific clock, machine code can "subclass" the
struct clock into a new struct (adding any device-specific data), and
provide a set of operations:

struct clk_foo {
	struct clk	clk;
	void __iomem	*some_register;
};

struct clk_ops clk_foo_ops = {
	.get_rate = clk_foo_get_rate,
};

The common clock definitions are based on a development patch from Ben
Herrenschmidt <benh@...nel.crashing.org>.

Signed-off-by: Jeremy Kerr <jeremy.kerr@...onical.com>

---
 arch/Kconfig        |    3 +
 include/linux/clk.h |   90 +++++++++++++++++++++++++++++++++++----
 kernel/Makefile     |    1 
 kernel/clk.c        |  101 ++++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 186 insertions(+), 9 deletions(-)

diff --git a/arch/Kconfig b/arch/Kconfig
index acda512..2458b5e 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -151,4 +151,7 @@ config HAVE_MIXED_BREAKPOINTS_REGS
 config HAVE_USER_RETURN_NOTIFIER
 	bool
 
+config USE_COMMON_STRUCT_CLK
+	bool
+
 source "kernel/gcov/Kconfig"
diff --git a/include/linux/clk.h b/include/linux/clk.h
index 1d37f42..a95cc82 100644
--- a/include/linux/clk.h
+++ b/include/linux/clk.h
@@ -3,6 +3,7 @@
  *
  *  Copyright (C) 2004 ARM Limited.
  *  Written by Deep Blue Solutions Limited.
+ *  Copyright (c) 2010 Jeremy Kerr <jeremy.kerr@...onical.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
@@ -11,18 +12,95 @@
 #ifndef __LINUX_CLK_H
 #define __LINUX_CLK_H
 
+#include <linux/err.h>
+#include <linux/mutex.h>
+
 struct device;
 
-/*
- * The base API.
+#ifdef CONFIG_USE_COMMON_STRUCT_CLK
+
+/* If we're using the common struct clk, we define the base clk object here */
+
+/**
+ * struct clk - hardware independent clock structure
+ * @clk_ops:		implementation-specific ops for this clock
+ * @enable_count:	count of clk_enable() calls active on this clock
+ * @mutex:		lock for enable/disable or other HW-specific ops
+ *
+ * The base clock object, used by drivers for hardware-independent manipulation
+ * of clock lines. This will be 'subclassed' by device-specific implementations,
+ * which add device-specific data to struct clk. For example:
+ *
+ *  struct clk_foo {
+ *      struct clk;
+ *      [device specific fields]
+ *  };
+ *
+ * The clock driver code will manage the device-specific data, and pass
+ * clk_foo.clk to the common clock code. The clock driver will be called
+ * through the @ops callbacks.
+ *
+ * The @enable_count and @mutex members are initialised when a clock is
+ * registered with the arch-specific clock management code; the clock driver
+ * code does not need to handle these.
  */
+struct clk {
+	const struct clk_ops	*ops;
+	unsigned int		enable_count;
+	struct mutex		mutex;
+};
+
+#define INIT_CLK(o) { .ops = &o, }
+
+struct clk_ops {
+       int		(*enable)(struct clk *);
+       void		(*disable)(struct clk *);
+       int		(*get)(struct clk *);
+       void		(*put)(struct clk *);
+       unsigned long	(*get_rate)(struct clk *);
+       long		(*round_rate)(struct clk *, unsigned long);
+       int		(*set_rate)(struct clk *, unsigned long);
+       int		(*set_parent)(struct clk *, struct clk *);
+       struct clk *	(*get_parent)(struct clk *);
+};
 
+/**
+ * __clk_get - update clock-specific refcounter
+ *
+ * @clk: The clock to refcount
+ *
+ * Before a clock is returned from clk_get, this function should be called
+ * to update any clock-specific refcounting.
+ *
+ * Returns non-zero on success, zero on failure.
+ *
+ * Drivers should not need this function; it is only needed by the
+ * arch-specific clk_get() implementations.
+ */
+int __clk_get(struct clk *clk);
+
+/**
+ * clk_common_init - initialise a clock for driver usage
+ *
+ * Used by arch code on registration with the clock infrastructure.
+ */
+static inline void clk_common_init(struct clk *clk)
+{
+	mutex_init(&clk->mutex);
+	clk->enable_count = 0;
+}
+
+#else /* !CONFIG_USE_COMMON_STRUCT_CLK */
 
 /*
- * struct clk - an machine class defined object / cookie.
+ * Global clock object, actual structure is declared per-machine
  */
 struct clk;
 
+static inline void clk_common_init(struct clk *clk) { }
+
+#endif /* !CONFIG_USE_COMMON_STRUCT_CLK */
+
 /**
  * clk_get - lookup and obtain a reference to a clock producer.
  * @dev: device for clock "consumer"
@@ -83,12 +161,6 @@ unsigned long clk_get_rate(struct clk *clk);
  */
 void clk_put(struct clk *clk);
 
-
-/*
- * The remaining APIs are optional for machine class support.
- */
-
-
 /**
  * clk_round_rate - adjust a rate to the exact rate a clock can provide
  * @clk: clock source
diff --git a/kernel/Makefile b/kernel/Makefile
index 057472f..1ae15aa 100644
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -105,6 +105,7 @@ obj-$(CONFIG_PERF_EVENTS) += perf_event.o
 obj-$(CONFIG_HAVE_HW_BREAKPOINT) += hw_breakpoint.o
 obj-$(CONFIG_USER_RETURN_NOTIFIER) += user-return-notifier.o
 obj-$(CONFIG_PADATA) += padata.o
+obj-$(CONFIG_USE_COMMON_STRUCT_CLK) += clk.o
 
 ifneq ($(CONFIG_SCHED_OMIT_FRAME_POINTER),y)
 # According to Alan Modra <alan@...uxcare.com.au>, the -fno-omit-frame-pointer is
diff --git a/kernel/clk.c b/kernel/clk.c
new file mode 100644
index 0000000..cdea25f
--- /dev/null
+++ b/kernel/clk.c
@@ -0,0 +1,101 @@
+/*
+ * Copyright (C) 2010 Canonical Ltd <jeremy.kerr@...onical.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.
+ *
+ * Standard functionality for the common clock API.
+ */
+
+#include <linux/clk.h>
+#include <linux/mutex.h>
+#include <linux/module.h>
+
+int clk_enable(struct clk *clk)
+{
+	int ret = 0;
+
+	if (!clk->ops->enable)
+		return 0;
+
+	mutex_lock(&clk->mutex);
+	if (!clk->enable_count)
+		ret = clk->ops->enable(clk);
+
+	if (!ret)
+		clk->enable_count++;
+	mutex_unlock(&clk->mutex);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(clk_enable);
+
+void clk_disable(struct clk *clk)
+{
+	if (!clk->ops->disable)
+		return;
+
+	mutex_lock(&clk->mutex);
+
+	if (!--clk->enable_count)
+		clk->ops->disable(clk);
+
+	mutex_unlock(&clk->mutex);
+}
+EXPORT_SYMBOL_GPL(clk_disable);
+
+unsigned long clk_get_rate(struct clk *clk)
+{
+	if (clk->ops->get_rate)
+		return clk->ops->get_rate(clk);
+	return 0;
+}
+EXPORT_SYMBOL_GPL(clk_get_rate);
+
+int __clk_get(struct clk *clk)
+{
+	if (clk->ops->get)
+		return clk->ops->get(clk);
+	return 1;
+}
+EXPORT_SYMBOL_GPL(__clk_get);
+
+void clk_put(struct clk *clk)
+{
+	if (clk->ops->put)
+		clk->ops->put(clk);
+}
+EXPORT_SYMBOL_GPL(clk_put);
+
+long clk_round_rate(struct clk *clk, unsigned long rate)
+{
+	if (clk->ops->round_rate)
+		return clk->ops->round_rate(clk, rate);
+	return -ENOSYS;
+}
+EXPORT_SYMBOL_GPL(clk_round_rate);
+
+int clk_set_rate(struct clk *clk, unsigned long rate)
+{
+	if (clk->ops->set_rate)
+		return clk->ops->set_rate(clk, rate);
+	return -ENOSYS;
+}
+EXPORT_SYMBOL_GPL(clk_set_rate);
+
+int clk_set_parent(struct clk *clk, struct clk *parent)
+{
+	if (clk->ops->set_parent)
+		return clk->ops->set_parent(clk, parent);
+	return -ENOSYS;
+}
+EXPORT_SYMBOL_GPL(clk_set_parent);
+
+struct clk *clk_get_parent(struct clk *clk)
+{
+	if (clk->ops->get_parent)
+		return clk->ops->get_parent(clk);
+	return ERR_PTR(-ENOSYS);
+}
+EXPORT_SYMBOL_GPL(clk_get_parent);
--
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