ARM: dts: s5pv210: add RTC 32 KHz clock in Aries family

[ Upstream commit 086c449 ]

The S3C RTC requires 32768 Hz clock as input which is provided by PMIC.
However there is no such clock provider but rather a regulator driver
which registers the clock as a regulator.  This is an old driver which
will not be updated so add a workaround - a fixed-clock to fill missing
clock phandle reference in S3C RTC.

This fixes dtbs_check warnings:

  rtc@e2800000: clocks: [[2, 145]] is too short
  rtc@e2800000: clock-names: ['rtc'] is too short

Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
Tested-by: Jonathan Bakker <xc-racer2@live.ca>
Link: https://lore.kernel.org/r/20200907161141.31034-12-krzk@kernel.org
Signed-off-by: Sasha Levin <sashal@kernel.org>

arch/arm/boot/dts/s5pv210-aries.dtsi

@@ -47,6 +47,13 @@
 		};
 	};
 
+	pmic_ap_clk: clock-0 {
+		/* Workaround for missing clock on PMIC */
+		compatible = "fixed-clock";
+		#clock-cells = <0>;
+		clock-frequency = <32768>;
+	};
+
 	bt_codec: bt_sco {
 		compatible = "linux,bt-sco";
 		#sound-dai-cells = <0>;
@@ -825,6 +832,11 @@
 	samsung,pwm-outputs = <1>;
 };
 
+&rtc {
+	clocks = <&clocks CLK_RTC>, <&pmic_ap_clk>;
+	clock-names = "rtc", "rtc_src";
+};
+
 &sdhci1 {
 	#address-cells = <1>;
 	#size-cells = <0>;