clk: add flag for clocks that need to be enabled on rate changes

Some clocks need to be enabled to accept rate changes. This patch adds a
new flag CLK_SET_RATE_UNGATE that lets clk_change_rate enable the clock
before trying to change the rate and disable it again afterwards.
This of course doesn't effect clocks that are already running at that
point, as their refcount will only temporarily increase.

Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Tested-by: Sjoerd Simons <sjoerd.simons@collabora.co.uk>
Reviewed-by: Sjoerd Simons <sjoerd.simons@collabora.co.uk>
Signed-off-by: Michael Turquette <mturquette@baylibre.com>

drivers/clk/clk.c

@@ -1443,6 +1443,15 @@ static void clk_change_rate(struct clk_core *core)
 	else if (core->parent)
 		best_parent_rate = core->parent->rate;
 
+	if (core->flags & CLK_SET_RATE_UNGATE) {
+		unsigned long flags;
+
+		clk_core_prepare(core);
+		flags = clk_enable_lock();
+		clk_core_enable(core);
+		clk_enable_unlock(flags);
+	}
+
 	if (core->new_parent && core->new_parent != core->parent) {
 		old_parent = __clk_set_parent_before(core, core->new_parent);
 		trace_clk_set_parent(core, core->new_parent);
@@ -1469,6 +1478,15 @@ static void clk_change_rate(struct clk_core *core)
 
 	core->rate = clk_recalc(core, best_parent_rate);
 
+	if (core->flags & CLK_SET_RATE_UNGATE) {
+		unsigned long flags;
+
+		flags = clk_enable_lock();
+		clk_core_disable(core);
+		clk_enable_unlock(flags);
+		clk_core_unprepare(core);
+	}
+
 	if (core->notifier_count && old_rate != core->rate)
 		__clk_notify(core, POST_RATE_CHANGE, old_rate, core->rate);
 

include/linux/clk-provider.h

@@ -31,6 +31,7 @@
 #define CLK_SET_RATE_NO_REPARENT BIT(7) /* don't re-parent on rate change */
 #define CLK_GET_ACCURACY_NOCACHE BIT(8) /* do not use the cached clk accuracy */
 #define CLK_RECALC_NEW_RATES	BIT(9) /* recalc rates after notifications */
+#define CLK_SET_RATE_UNGATE	BIT(10) /* clock needs to run to set rate */
 
 struct clk;
 struct clk_hw;