[PATCH v6 1/5] clk: Provide not locked variant of of_clk_get_from_provider()

Sylwester Nawrocki
2013-08-30T14:53:18Z

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>
---
Changes since v3:
- none.

Changes since v2:
- fixed typo in clk.h.

Changes since v1:
- moved the function declaractions to a local header.
---
drivers/clk/clk.c | 38 ++++++++++++++++++++++++++++++--------
drivers/clk/clk.h | 16 ++++++++++++++++
2 files changed, 46 insertions(+), 8 deletions(-)
create mode 100644 drivers/clk/clk.h

diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
index 2db08c0..8f18564 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);

@@ -2103,7 +2105,18 @@ 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)
@@ -2147,9 +2160,9 @@ 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;
@@ -2164,7 +2177,7 @@ 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);
@@ -2173,24 +2186,33 @@ 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 0000000..795cc9f
--- /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
--
1.7.9.5