apm821xx: set uart compatible to ns16750

The APM821XX/PPC460EX datasheet mentions:
"Register compatibility with 16750 register set"

Signed-off-by: Christian Lamparter <chunkeey@gmail.com>
(backported from 68bb91018df1c3d9474041a4d55e1cfd66022522)

diff --git a/target/linux/apm821xx/dts/apm82181.dtsi b/target/linux/apm821xx/dts/apm82181.dtsi
index be8ace9207c0517b772e223bc3f647836198633a..79596da672b7d4db1d8a8e21db7abd78f44a461a 100644 (file)
--- a/target/linux/apm821xx/dts/apm82181.dtsi
+++ b/target/linux/apm821xx/dts/apm82181.dtsi
@@ -306,24 +306,29 @@
                        };
 
                        UART0: serial@ef600300 {
-                               device_type = "serial";
-                               compatible = "ns16550";
+                               /*
+                                * AMCC's BSP u-boot scans for the "ns16550"
+                                * compatible, without it, u-boot wouldn't
+                                * set the "clock-frequency" which is required.
+                                *
+                                * However, the hardware documentation lists:
+                                * "Register compatibility with 16750 register set"
+                                */
+                               compatible = "ns16750", "ns16550";
                                reg = <0xef600300 0x00000008>;
                                virtual-reg = <0xef600300>;
                                clock-frequency = <0>; /* Filled in by U-Boot */
-                               current-speed = <0>; /* Filled in by U-Boot */
                                interrupt-parent = <&UIC1>;
                                interrupts = <0x01 IRQ_TYPE_LEVEL_HIGH>;
                                status = "disabled";
                        };
 
                        UART1: serial@ef600400 {
-                               device_type = "serial";
-                               compatible = "ns16550";
+                               /* same "ns16750" as with UART0 */
+                               compatible = "ns16750", "ns16550";
                                reg = <0xef600400 0x00000008>;
                                virtual-reg = <0xef600400>;
                                clock-frequency = <0>; /* Filled in by U-Boot */
-                               current-speed = <0>; /* Filled in by U-Boot */
                                interrupt-parent = <&UIC0>;
                                interrupts = <0x01 IRQ_TYPE_LEVEL_HIGH>;
                                status = "disabled";