clk: fix clk_get on of_clk_get_by_name return check

The commit 766e6a4 (clk: add DT clock binding support) plugs device
tree clk lookup of_clk_get_by_name into clk_get, and fall on non-DT
lookup clk_get_sys if DT lookup fails.

The return check on of_clk_get_by_name takes (clk != NULL) as a
successful DT lookup.  But it's not the case.  For any system that
does not define clk lookup in device tree, ERR_PTR(-ENOENT) will be
returned, and consequently, all the client drivers calling clk_get
in their probe functions will fail to probe with error code -ENOENT
returned.

Fix the issue by checking of_clk_get_by_name return with !IS_ERR(clk),
and update of_clk_get and of_clk_get_by_name for !CONFIG_OF build
correspondingly.

Signed-off-by: Shawn Guo <shawn.guo@linaro.org>
Acked-by: Rob Herring <rob.herring@calxeda.com>
Tested-by: Marek Vasut <marex@denx.de>
Tested-by: Lauri Hintsala <lauri.hintsala@bluegiga.com>
Signed-off-by: Mike Turquette <mturquette@linaro.org>

1 files changed, 3 insertions, 2 deletions

diff --git a/include/linux/clk.h b/include/linux/clk.h
index 8b70342e7e0b..071e24083dc8 100644
--- a/include/linux/clk.h
+++ b/include/linux/clk.h
@@ -12,6 +12,7 @@
 #ifndef __LINUX_CLK_H
 #define __LINUX_CLK_H
 
+#include <linux/err.h>
 #include <linux/kernel.h>
 #include <linux/notifier.h>
 
@@ -320,12 +321,12 @@ struct clk *of_clk_get_from_provider(struct of_phandle_args *clkspec);
 #else
 static inline struct clk *of_clk_get(struct device_node *np, int index)
 {
-        return NULL;
+        return ERR_PTR(-ENOENT);
 }
 static inline struct clk *of_clk_get_by_name(struct device_node *np,
                                              const char *name)
 {
-        return NULL;
+        return ERR_PTR(-ENOENT);
 }
 #endif