MIPS: qi_lb60: Reduce system timer and clocksource to 750 kHz

The default clock (12 MHz) is too fast for the system timer, which fails
to report time accurately.

Signed-off-by: Paul Cercueil <paul@crapouillou.net>
Tested-by: Mathieu Malaterre <malat@debian.org>
Tested-by: Artur Rojek <contact@artur-rojek.eu>
Signed-off-by: Paul Burton <paul.burton@mips.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: James Hogan <jhogan@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Lee Jones <lee.jones@linaro.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Michael Turquette <mturquette@baylibre.com>
Cc: Stephen Boyd <sboyd@kernel.org>
Cc: Jason Cooper <jason@lakedaemon.net>
Cc: Marc Zyngier <marc.zyngier@arm.com>
Cc: Rob Herring <robh+dt@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: devicetree@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: linux-doc@vger.kernel.org
Cc: linux-mips@vger.kernel.org
Cc: linux-clk@vger.kernel.org
Cc: od@zcrc.me

arch/mips/boot/dts/ingenic/qi_lb60.dts

@@ -2,6 +2,7 @@
 /dts-v1/;
 
 #include "jz4740.dtsi"
+#include <dt-bindings/clock/ingenic,tcu.h>
 
 / {
 	compatible = "qi,lb60", "ingenic,jz4740";
@@ -31,3 +32,9 @@
 		bias-disable;
 	};
 };
+
+&tcu {
+	/* 750 kHz for the system timer and clocksource */
+	assigned-clocks = <&tcu TCU_CLK_TIMER0>, <&tcu TCU_CLK_TIMER1>;
+	assigned-clock-rates = <750000>, <750000>;
+};