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Re: [PATCH] generic clk API implementation for MIPS

To: vagabon.xyz@gmail.com
Subject: Re: [PATCH] generic clk API implementation for MIPS
From: Atsushi Nemoto <anemo@mba.ocn.ne.jp>
Date: Tue, 26 Jun 2007 23:33:32 +0900 (JST)
Cc: linux-mips@linux-mips.org, ralf@linux-mips.org
In-reply-to: <cda58cb80706260237r60a0b6b3obeba7daac7cf114a@mail.gmail.com>
Original-recipient: rfc822;linux-mips@linux-mips.org
References: <20070626.011449.132112302.anemo@mba.ocn.ne.jp> <cda58cb80706260237r60a0b6b3obeba7daac7cf114a@mail.gmail.com>
Sender: linux-mips-bounce@linux-mips.org
On Tue, 26 Jun 2007 11:37:31 +0200, "Franck Bui-Huu" <vagabon.xyz@gmail.com> 
wrote:
> Did you consider Atmel implementation which is even more stripped ?

Well, it seems simpler, but I suppose clk_register() is very useful ;)

> The main difference seems that your version has module support. I'm
> not sure how usefull it is though.

Indeed.  Revised.


Subject: [PATCH] generic clk API implementation for MIPS

The clock framework (clk_get(), etc.) would be useful to provide some
clock values to platform devices or so.

This MIPS implementation is derived (and stripped) from the SH
implementation.

Signed-off-by: Atsushi Nemoto <anemo@mba.ocn.ne.jp>
---
 arch/mips/lib/Makefile   |    2 +-
 arch/mips/lib/clock.c    |  185 ++++++++++++++++++++++++++++++++++++++++++++++
 include/asm-mips/clock.h |   38 ++++++++++
 3 files changed, 224 insertions(+), 1 deletions(-)

diff --git a/arch/mips/lib/Makefile b/arch/mips/lib/Makefile
index a960c05..ecea595 100644
--- a/arch/mips/lib/Makefile
+++ b/arch/mips/lib/Makefile
@@ -3,7 +3,7 @@
 #
 
 lib-y  += csum_partial.o memcpy.o memcpy-inatomic.o memset.o strlen_user.o \
-          strncpy_user.o strnlen_user.o uncached.o
+          strncpy_user.o strnlen_user.o uncached.o clock.o
 
 obj-y                  += iomap.o
 obj-$(CONFIG_PCI)      += iomap-pci.o
diff --git a/arch/mips/lib/clock.c b/arch/mips/lib/clock.c
new file mode 100644
index 0000000..2bfd0b4
--- /dev/null
+++ b/arch/mips/lib/clock.c
@@ -0,0 +1,185 @@
+/*
+ * arch/mips/lib/clock.c - MIPS clock framework
+ *
+ * This clock framework is derived from the SH version by:
+ *
+ *  Copyright (C) 2005, 2006  Paul Mundt
+ *
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License.  See the file "COPYING" in the main directory of this archive
+ * for more details.
+ */
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/mutex.h>
+#include <linux/list.h>
+#include <linux/kref.h>
+#include <linux/err.h>
+#include <linux/platform_device.h>
+#include <asm/clock.h>
+
+static LIST_HEAD(clock_list);
+static DEFINE_SPINLOCK(clock_lock);
+static DEFINE_MUTEX(clock_list_lock);
+
+static int __clk_enable(struct clk *clk)
+{
+       /*
+        * See if this is the first time we're enabling the clock, some
+        * clocks that are always enabled still require "special"
+        * initialization. This is especially true if the clock mode
+        * changes and the clock needs to hunt for the proper set of
+        * divisors to use before it can effectively recalc.
+        */
+       if (unlikely(atomic_read(&clk->kref.refcount) == 1))
+               if (clk->ops && clk->ops->init)
+                       clk->ops->init(clk);
+
+       if (clk->flags & CLK_ALWAYS_ENABLED)
+               return 0;
+
+       if (likely(clk->ops && clk->ops->enable))
+               clk->ops->enable(clk);
+
+       kref_get(&clk->kref);
+       return 0;
+}
+
+int clk_enable(struct clk *clk)
+{
+       unsigned long flags;
+       int ret;
+
+       spin_lock_irqsave(&clock_lock, flags);
+       ret = __clk_enable(clk);
+       spin_unlock_irqrestore(&clock_lock, flags);
+
+       return ret;
+}
+EXPORT_SYMBOL_GPL(clk_enable);
+
+static void clk_kref_release(struct kref *kref)
+{
+       /* Nothing to do */
+}
+
+static void __clk_disable(struct clk *clk)
+{
+       if (clk->flags & CLK_ALWAYS_ENABLED)
+               return;
+
+       kref_put(&clk->kref, clk_kref_release);
+}
+
+void clk_disable(struct clk *clk)
+{
+       unsigned long flags;
+
+       spin_lock_irqsave(&clock_lock, flags);
+       __clk_disable(clk);
+       spin_unlock_irqrestore(&clock_lock, flags);
+}
+EXPORT_SYMBOL_GPL(clk_disable);
+
+int clk_register(struct clk *clk)
+{
+       mutex_lock(&clock_list_lock);
+
+       list_add(&clk->node, &clock_list);
+       kref_init(&clk->kref);
+
+       mutex_unlock(&clock_list_lock);
+
+       return 0;
+}
+EXPORT_SYMBOL_GPL(clk_register);
+
+void clk_unregister(struct clk *clk)
+{
+       mutex_lock(&clock_list_lock);
+       list_del(&clk->node);
+       mutex_unlock(&clock_list_lock);
+}
+EXPORT_SYMBOL_GPL(clk_unregister);
+
+unsigned long clk_get_rate(struct clk *clk)
+{
+       return clk->rate;
+}
+EXPORT_SYMBOL_GPL(clk_get_rate);
+
+int clk_set_rate(struct clk *clk, unsigned long rate)
+{
+       int ret = -EOPNOTSUPP;
+
+       if (likely(clk->ops && clk->ops->set_rate)) {
+               unsigned long flags;
+
+               spin_lock_irqsave(&clock_lock, flags);
+               ret = clk->ops->set_rate(clk, rate);
+               spin_unlock_irqrestore(&clock_lock, flags);
+       }
+
+       return ret;
+}
+EXPORT_SYMBOL_GPL(clk_set_rate);
+
+/*
+ * Returns a clock. Note that we first try to use device id on the bus
+ * and clock name. If this fails, we try to use clock name only.
+ */
+struct clk *clk_get(struct device *dev, const char *id)
+{
+       struct clk *p, *clk = ERR_PTR(-ENOENT);
+       int idno;
+
+       if (dev == NULL || dev->bus != &platform_bus_type)
+               idno = -1;
+       else
+               idno = to_platform_device(dev)->id;
+
+       mutex_lock(&clock_list_lock);
+       list_for_each_entry(p, &clock_list, node) {
+               if (p->id == idno && strcmp(id, p->name) == 0) {
+                       clk = p;
+                       goto found;
+               }
+       }
+
+       list_for_each_entry(p, &clock_list, node) {
+               if (strcmp(id, p->name) == 0) {
+                       clk = p;
+                       break;
+               }
+       }
+
+found:
+       mutex_unlock(&clock_list_lock);
+
+       return clk;
+}
+EXPORT_SYMBOL_GPL(clk_get);
+
+void clk_put(struct clk *clk)
+{
+}
+EXPORT_SYMBOL_GPL(clk_put);
+
+long clk_round_rate(struct clk *clk, unsigned long rate)
+{
+       return rate;
+}
+EXPORT_SYMBOL_GPL(clk_round_rate);
+
+int clk_set_parent(struct clk *clk, struct clk *parent)
+{
+       clk->parent = parent;
+       return 0;
+}
+EXPORT_SYMBOL_GPL(clk_set_parent);
+
+struct clk *clk_get_parent(struct clk *clk)
+{
+       return clk->parent ?: ERR_PTR(-ENODEV);
+}
+EXPORT_SYMBOL_GPL(clk_get_parent);
diff --git a/include/asm-mips/clock.h b/include/asm-mips/clock.h
new file mode 100644
index 0000000..1c1429b
--- /dev/null
+++ b/include/asm-mips/clock.h
@@ -0,0 +1,38 @@
+#ifndef __ASM_MIPS_CLOCK_H
+#define __ASM_MIPS_CLOCK_H
+
+/* generic clk API implementation --- derived from include/asm-sh/clock.h */
+
+#include <linux/kref.h>
+#include <linux/list.h>
+#include <linux/clk.h>
+
+struct clk;
+
+struct clk_ops {
+       void (*init)(struct clk *clk);
+       void (*enable)(struct clk *clk);
+       void (*disable)(struct clk *clk);
+       int (*set_rate)(struct clk *clk, unsigned long rate);
+};
+
+struct clk {
+       struct list_head        node;
+       const char              *name;
+       int                     id;
+
+       struct clk              *parent;
+       struct clk_ops          *ops;
+
+       struct kref             kref;
+
+       unsigned long           rate;
+       unsigned long           flags;
+};
+
+#define CLK_ALWAYS_ENABLED     (1 << 0)
+
+int clk_register(struct clk *);
+void clk_unregister(struct clk *);
+
+#endif /* __ASM_MIPS_CLOCK_H */

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