rtc: sun6i: Expose internal oscillator through device tree

The bindings have been updated to expose the RTC's internal oscillator,
for some SoCs that have it directly feeding the PRCM block. The changes
include the index 2 for the clock outputs, as well as the clock output
names.

This patch adds the internal oscillator to the list of clocks exposed
through of_clk_add_hw_provider(), and also have the driver optionally
fetch the name of the clock from the device tree if it's available.
Tested-by: Corentin Labbe <clabbe.montjoie@gmail.com>
Signed-off-by: Chen-Yu Tsai <wens@csie.org>
Acked-by: Maxime Ripard <maxime.ripard@bootlin.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

drivers/rtc/rtc-sun6i.c

@@ -136,6 +136,7 @@ struct sun6i_rtc_clk_data {
 	unsigned int fixed_prescaler : 16;
 	unsigned int has_prescaler : 1;
 	unsigned int has_out_clk : 1;
+	unsigned int export_iosc : 1;
 };
 
 struct sun6i_rtc_dev {
@@ -220,6 +221,7 @@ static void __init sun6i_rtc_clk_init(struct device_node *node,
 		.ops		= &sun6i_rtc_osc_ops,
 		.name		= "losc",
 	};
+	const char *iosc_name = "rtc-int-osc";
 	const char *clkout_name = "osc32k-out";
 	const char *parents[2];
 
@@ -228,7 +230,7 @@ static void __init sun6i_rtc_clk_init(struct device_node *node,
 		return;
 
 	rtc->data = data;
-	clk_data = kzalloc(struct_size(clk_data, hws, 2), GFP_KERNEL);
+	clk_data = kzalloc(struct_size(clk_data, hws, 3), GFP_KERNEL);
 	if (!clk_data) {
 		kfree(rtc);
 		return;
@@ -253,8 +255,13 @@ static void __init sun6i_rtc_clk_init(struct device_node *node,
 	if (!of_get_property(node, "clocks", NULL))
 		goto err;
 
+	/* Only read IOSC name from device tree if it is exported */
+	if (rtc->data->export_iosc)
+		of_property_read_string_index(node, "clock-output-names", 2,
+					      &iosc_name);
+
 	rtc->int_osc = clk_hw_register_fixed_rate_with_accuracy(NULL,
-								"rtc-int-osc",
+								iosc_name,
 								NULL, 0,
 								rtc->data->rc_osc_rate,
 								300000000);
@@ -293,6 +300,10 @@ static void __init sun6i_rtc_clk_init(struct device_node *node,
 	clk_data->num = 2;
 	clk_data->hws[0] = &rtc->hw;
 	clk_data->hws[1] = __clk_get_hw(rtc->ext_losc);
+	if (rtc->data->export_iosc) {
+		clk_data->hws[2] = rtc->int_osc;
+		clk_data->num = 3;
+	}
 	of_clk_add_hw_provider(node, of_clk_hw_onecell_get, clk_data);
 	return;
 
@@ -330,6 +341,7 @@ static const struct sun6i_rtc_clk_data sun8i_h3_rtc_data = {
 	.fixed_prescaler = 32,
 	.has_prescaler = 1,
 	.has_out_clk = 1,
+	.export_iosc = 1,
 };
 
 static void __init sun8i_h3_rtc_clk_init(struct device_node *node)