clk: add clk_ignore_unused option to keep boot clocks on

This is primarily useful when there's a driver that doesn't claim clocks
properly, but the bootloader leaves them on. It's not expected to be used
in normal cases, but for bringup and debug it's very useful to have the
option to not gate unclaimed clocks that are still on.

Signed-off-by: Olof Johansson <olof@lixom.net>
Signed-off-by: Mike Turquette <mturquette@linaro.org>
[mturquette@linaro.org: fixed up trivial merge issue]

drivers/clk/clk.c

@@ -499,10 +499,23 @@ out:
 	return;
 }
 
+static bool clk_ignore_unused;
+static int __init clk_ignore_unused_setup(char *__unused)
+{
+	clk_ignore_unused = true;
+	return 1;
+}
+__setup("clk_ignore_unused", clk_ignore_unused_setup);
+
 static int clk_disable_unused(void)
 {
 	struct clk *clk;
 
+	if (clk_ignore_unused) {
+		pr_warn("clk: Not disabling unused clocks\n");
+		return 0;
+	}
+
 	clk_prepare_lock();
 
 	hlist_for_each_entry(clk, &clk_root_list, child_node)