ARM: dts: sun9i: Add TODO comments for the main and low power clocks

The main (24MHz) clock on the A80 is configurable via the PRCM address
space. The low power/speed (32kHz) clock is from an external chip, the
AC100.

Signed-off-by: Chen-Yu Tsai <wens@csie.org>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>

diff --git a/arch/arm/boot/dts/sun9i-a80.dtsi b/arch/arm/boot/dts/sun9i-a80.dtsi
index a4ce348c083160ece6e0e48e92fafa991a858c55..eb69a62f6bc47474396ef6066d1b291ecd7bf270 100644 (file)
--- a/arch/arm/boot/dts/sun9i-a80.dtsi
+++ b/arch/arm/boot/dts/sun9i-a80.dtsi
@@ -128,6 +128,17 @@
                 */
                ranges = <0 0 0 0x20000000>;
 
+               /*
+                * This clock is actually configurable from the PRCM address
+                * space. The external 24M oscillator can be turned off, and
+                * the clock switched to an internal 16M RC oscillator. Under
+                * normal operation there's no reason to do this, and the
+                * default is to use the external good one, so just model this
+                * as a fixed clock. Also it is not entirely clear if the
+                * osc24M mux in the PRCM affects the entire clock tree, which
+                * would also throw all the PLL clock rates off, or just the
+                * downstream clocks in the PRCM.
+                */
                osc24M: osc24M_clk {
                        #clock-cells = <0>;
                        compatible = "fixed-clock";
@@ -135,6 +146,13 @@
                        clock-output-names = "osc24M";
                };
 
+               /*
+                * The 32k clock is from an external source, normally the
+                * AC100 codec/RTC chip. This clock is by default enabled
+                * and clocked at 32768 Hz, from the oscillator connected
+                * to the AC100. It is configurable, but no such driver or
+                * bindings exist yet.
+                */
                osc32k: osc32k_clk {
                        #clock-cells = <0>;
                        compatible = "fixed-clock";