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[PATCH v4 1/5] clk: Provide not locked variant of of_clk_get_from_provid

To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH v4 1/5] clk: Provide not locked variant of of_clk_get_from_provider()
From: Sylwester Nawrocki <sylvester.nawrocki@gmail.com>
Date: Sat, 24 Aug 2013 17:19:45 +0200
Cc: linux@arm.linux.org.uk, mturquette@linaro.org, jiada_wang@mentor.com, broonie@kernel.org, vapier@gentoo.org, ralf@linux-mips.org, kyungmin.park@samsung.com, myungjoo.ham@samsung.com, shawn.guo@linaro.org, sebastian.hesselbarth@gmail.com, LW@KARO-electronics.de, t.figa@samsung.com, g.liakhovetski@gmx.de, laurent.pinchart@ideasonboard.com, linux-kernel@vger.kernel.org, uclinux-dist-devel@blackfin.uclinux.org, linux-mips@linux-mips.org, linux-sh@vger.kernel.org, s.nawrocki@samsung.com
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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 bc02037..f46444f 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);
 
@@ -2097,7 +2099,18 @@ 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)
@@ -2141,9 +2154,9 @@ 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;
@@ -2158,7 +2171,7 @@ 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);
@@ -2167,24 +2180,33 @@ 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
-- 
1.7.4.1


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