clk: samsung: Add support for EPLL on exynos5410

This patch adds code instantiating the EPLL, which is used as the
audio subsystem's root clock.
The requirement to specify the external root clock in clocks property
is documented.  Having the consumer 'clocks' property ensures proper
initialization order by explicitly specifying dependencies in DT.
It prevents situations when the SoC's clock controller driver has
initialized, the external oscillator clock is not yet registered
and setting clock frequencies through assigned-clock-rates property
doesn't work properly due to unknown external oscillator frequency.

Signed-off-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
Reviewed-by: Chanwoo Choi <cw00.choi@samsung.com>

1 files changed, 13 insertions, 8 deletions

diff --git a/Documentation/devicetree/bindings/clock/exynos5410-clock.txt b/Documentation/devicetree/bindings/clock/exynos5410-clock.txt
index aeab635b07b5..4527de3ea205 100644
--- a/Documentation/devicetree/bindings/clock/exynos5410-clock.txt
+++ b/Documentation/devicetree/bindings/clock/exynos5410-clock.txt
@@ -12,24 +12,29 @@ Required Properties:
 
 - #clock-cells: should be 1.
 
+- clocks: should contain an entry specifying the root clock from external
+  oscillator supplied through XXTI or XusbXTI pin.  This clock should be
+  defined using standard clock bindings with "fin_pll" clock-output-name.
+  That clock is being passed internally to the 9 PLLs.
+
 All available clocks are defined as preprocessor macros in
 dt-bindings/clock/exynos5410.h header and can be used in device
 tree sources.
 
-External clock:
-
-There is clock that is generated outside the SoC. It
-is expected that it is defined using standard clock bindings
-with following clock-output-name:
-
- - "fin_pll" - PLL input clock from XXTI
-
 Example 1: An example of a clock controller node is listed below.
 
+	fin_pll: xxti {
+		compatible = "fixed-clock";
+		clock-frequency = <24000000>;
+		clock-output-names = "fin_pll";
+		#clock-cells = <0>;
+	};
+
 	clock: clock-controller@0x10010000 {
 		compatible = "samsung,exynos5410-clock";
 		reg = <0x10010000 0x30000>;
 		#clock-cells = <1>;
+		clocks = <&fin_pll>;
 	};
 
 Example 2: UART controller node that consumes the clock generated by the clock