clk: Provide not locked variant of of_clk_get_from_provider()

Add helper functions for the of_clk_providers list locking and
an unlocked variant of of_clk_get_from_provider().
These functions are intended to be used in the clkdev to avoid
race condition in the device tree based clock look up in clk_get().

Signed-off-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Acked-by: Russell King <rmk+kernel@arm.linux.org.uk>

2 files changed, 46 insertions, 8 deletions

diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
index 77fcd069c64a..c687dc8d0b64 100644
--- a/drivers/clk/clk.c
+++ b/drivers/clk/clk.c
@@ -21,6 +21,8 @@
 #include <linux/init.h>
 #include <linux/sched.h>
 
+#include "clk.h"
+
 static DEFINE_SPINLOCK(enable_lock);
 static DEFINE_MUTEX(prepare_lock);
 
@@ -2111,7 +2113,18 @@ static const struct of_device_id __clk_of_table_sentinel
         __used __section(__clk_of_table_end);
 
 static LIST_HEAD(of_clk_providers);
-static DEFINE_MUTEX(of_clk_lock);
+static DEFINE_MUTEX(of_clk_mutex);
+
+/* of_clk_provider list locking helpers */
+void of_clk_lock(void)
+{
+        mutex_lock(&of_clk_mutex);
+}
+
+void of_clk_unlock(void)
+{
+        mutex_unlock(&of_clk_mutex);
+}
 
 struct clk *of_clk_src_simple_get(struct of_phandle_args *clkspec,
                                      void *data)
@@ -2155,9 +2168,9 @@ int of_clk_add_provider(struct device_node *np,
         cp->data = data;
         cp->get = clk_src_get;
 
-        mutex_lock(&of_clk_lock);
+        mutex_lock(&of_clk_mutex);
         list_add(&cp->link, &of_clk_providers);
-        mutex_unlock(&of_clk_lock);
+        mutex_unlock(&of_clk_mutex);
         pr_debug("Added clock from %s\n", np->full_name);
 
         return 0;
@@ -2172,7 +2185,7 @@ void of_clk_del_provider(struct device_node *np)
 {
         struct of_clk_provider *cp;
 
-        mutex_lock(&of_clk_lock);
+        mutex_lock(&of_clk_mutex);
         list_for_each_entry(cp, &of_clk_providers, link) {
                 if (cp->node == np) {
                         list_del(&cp->link);
@@ -2181,24 +2194,33 @@ void of_clk_del_provider(struct device_node *np)
                         break;
                 }
         }
-        mutex_unlock(&of_clk_lock);
+        mutex_unlock(&of_clk_mutex);
 }
 EXPORT_SYMBOL_GPL(of_clk_del_provider);
 
-struct clk *of_clk_get_from_provider(struct of_phandle_args *clkspec)
+struct clk *__of_clk_get_from_provider(struct of_phandle_args *clkspec)
 {
         struct of_clk_provider *provider;
         struct clk *clk = ERR_PTR(-ENOENT);
 
         /* Check if we have such a provider in our array */
-        mutex_lock(&of_clk_lock);
         list_for_each_entry(provider, &of_clk_providers, link) {
                 if (provider->node == clkspec->np)
                         clk = provider->get(clkspec, provider->data);
                 if (!IS_ERR(clk))
                         break;
         }
-        mutex_unlock(&of_clk_lock);
+
+        return clk;
+}
+
+struct clk *of_clk_get_from_provider(struct of_phandle_args *clkspec)
+{
+        struct clk *clk;
+
+        mutex_lock(&of_clk_mutex);
+        clk = __of_clk_get_from_provider(clkspec);
+        mutex_unlock(&of_clk_mutex);
 
         return clk;
 }
diff --git a/drivers/clk/clk.h b/drivers/clk/clk.h
new file mode 100644
index 000000000000..795cc9f0dac0
--- /dev/null
+++ b/drivers/clk/clk.h
@@ -0,0 +1,16 @@
+/*
+ * linux/drivers/clk/clk.h
+ *
+ * Copyright (C) 2013 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.
+ */
+
+#if defined(CONFIG_OF) && defined(CONFIG_COMMON_CLK)
+struct clk *__of_clk_get_from_provider(struct of_phandle_args *clkspec);
+void of_clk_lock(void);
+void of_clk_unlock(void);
+#endif