serial: vt8500: UART uses gated clock rather than 24Mhz reference

UART modules on Wondermedia SoCs are connected via a gated clock
source, rather than directly to the 24Mhz reference clock. While
uboot enables UART0 for debugging, other UART ports are unavailable
until the clock is enabled.

This patch checks that a valid clock is actually passed from devicetree,
enables the clock in probe. This change removes the fallback when a
clock was not specified as it doesn't apply any longer (and would only
work if the UART clock was already enabled).

DTSI files are updated for VT8500, WM8505 and WM8650.

Signed-off-by: Tony Prisk <linux@prisktech.co.nz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 18 insertions, 2 deletions

diff --git a/arch/arm/boot/dts/wm8650.dtsi b/arch/arm/boot/dts/wm8650.dtsi
index 83b9467559bb..db3c0a12e052 100644
--- a/arch/arm/boot/dts/wm8650.dtsi
+++ b/arch/arm/boot/dts/wm8650.dtsi
@@ -75,6 +75,22 @@
                                         reg = <0x204>;
                                 };
 
+                                clkuart0: uart0 {
+                                        #clock-cells = <0>;
+                                        compatible = "via,vt8500-device-clock";
+                                        clocks = <&ref24>;
+                                        enable-reg = <0x250>;
+                                        enable-bit = <1>;
+                                };
+
+                                clkuart1: uart1 {
+                                        #clock-cells = <0>;
+                                        compatible = "via,vt8500-device-clock";
+                                        clocks = <&ref24>;
+                                        enable-reg = <0x250>;
+                                        enable-bit = <2>;
+                                };
+
                                 arm: arm {
                                         #clock-cells = <0>;
                                         compatible = "via,vt8500-device-clock";
@@ -128,14 +144,14 @@
                         compatible = "via,vt8500-uart";
                         reg = <0xd8200000 0x1040>;
                         interrupts = <32>;
-                        clocks = <&ref24>;
+                        clocks = <&clkuart0>;
                 };
 
                 uart@d82b0000 {
                         compatible = "via,vt8500-uart";
                         reg = <0xd82b0000 0x1040>;
                         interrupts = <33>;
-                        clocks = <&ref24>;
+                        clocks = <&clkuart1>;
                 };
 
                 rtc@d8100000 {