[PATCH] clk: fix clk-gpio.c with optional clock= DT property

[Russell King]

When the clock DT property is not given, of_clk_get_parent_count()
returns -ENOENT, which then tries to allocate -2 x 4 bytes of memory,
which of course fails, causing the whole driver to fail to create
the clock.

This causes the SolidRun platforms to fail probing the SDHCI1 interface
which is connected to the WiFi.

Fix this by detecting errno codes, skipping the allocation, and fixing
of_clk_gpio_gate_delayed_register_get() to handle a NULL parent_names
array.

Fixes: 80eeb1f0f757 ("clk: add gpio controlled clock multiplexer")
Signed-off-by: Russell King <rmk+kernel at arm.linux.org.uk>
---
This goes all the way back to 80eeb1f0f757 ("clk: add gpio controlled
clock multiplexer") introduced in June in v4.3-rc2 - which raises the
question why _development_ work in clk is being merged outside of the
merge window.

A rewrite of this patch will be necessary to apply to v4.3 kernels.

This applies on top of v4.4-rc6.

 drivers/clk/clk-gpio.c | 23 ++++++++++++++---------
 1 file changed, 14 insertions(+), 9 deletions(-)

diff --git a/drivers/clk/clk-gpio.c b/drivers/clk/clk-gpio.c
index 335322dc403f..05cca9298f44 100644
--- a/drivers/clk/clk-gpio.c
+++ b/drivers/clk/clk-gpio.c
@@ -264,8 +264,8 @@ static struct clk *of_clk_gpio_gate_delayed_register_get(const char *name,
 		const char * const *parent_names, u8 num_parents,
 		unsigned gpio, bool active_low)
 {
-	return clk_register_gpio_gate(NULL, name, parent_names[0],
-			gpio, active_low, 0);
+	return clk_register_gpio_gate(NULL, name, parent_names ?
+			parent_names[0] : NULL, gpio, active_low, 0);
 }
 
 static struct clk *of_clk_gpio_mux_delayed_register_get(const char *name,
@@ -292,13 +292,18 @@ static void __init of_gpio_clk_setup(struct device_node *node,
 		return;
 
 	num_parents = of_clk_get_parent_count(node);
-
-	parent_names = kcalloc(num_parents, sizeof(char *), GFP_KERNEL);
-	if (!parent_names)
-		return;
-
-	for (i = 0; i < num_parents; i++)
-		parent_names[i] = of_clk_get_parent_name(node, i);
+	if (num_parents > 0) {
+		parent_names = kcalloc(num_parents, sizeof(char *), GFP_KERNEL);
+		if (!parent_names) {
+			kfree(data);
+			return;
+		}
+
+		for (i = 0; i < num_parents; i++)
+			parent_names[i] = of_clk_get_parent_name(node, i);
+	} else {
+		parent_names = NULL;
+	}
 
 	data->num_parents = num_parents;
 	data->parent_names = parent_names;
-- 
2.1.0