arm64: dts: amlogic: gxl: enable UART RX and TX pull up by default

Some boards have noise on the UART RX line when the UART pins are not
connected to another device (such as an USB UART adapter). This can
be addressed by using a pull up resistor. Not all boards may provide
such a pull up resistor on the PCB so enable the SoC's pull-up on the
UART RX and TX pads by default. This matches the default (from u-boot
or SoC hardware) state for the pinmux configuration on these pads.

Signed-off-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Reviewed-by: Neil Armstrong <neil.armstrong@linaro.org>
Link: https://lore.kernel.org/r/20250329185855.854186-5-martin.blumenstingl@googlemail.com
Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>

diff --git a/arch/arm64/boot/dts/amlogic/meson-gxl.dtsi b/arch/arm64/boot/dts/amlogic/meson-gxl.dtsi
index 2dc2fdaecf9ff5e9c1798f23ad33bc3eef24b6a0..460c46cfad6a7ce909a746aa4a8f0dff880ad6d1 100644 (file)
--- a/arch/arm64/boot/dts/amlogic/meson-gxl.dtsi
+++ b/arch/arm64/boot/dts/amlogic/meson-gxl.dtsi
@@ -163,7 +163,7 @@
                        mux {
                                groups = "uart_tx_ao_a", "uart_rx_ao_a";
                                function = "uart_ao";
-                               bias-disable;
+                               bias-pull-up;
                        };
                };
 
@@ -180,7 +180,7 @@
                        mux {
                                groups = "uart_tx_ao_b", "uart_rx_ao_b";
                                function = "uart_ao_b";
-                               bias-disable;
+                               bias-pull-up;
                        };
                };
 
@@ -188,7 +188,7 @@
                        mux {
                                groups = "uart_tx_ao_b_0", "uart_rx_ao_b_1";
                                function = "uart_ao_b";
-                               bias-disable;
+                               bias-pull-up;
                        };
                };
 
@@ -522,7 +522,7 @@
                                groups = "uart_tx_a",
                                       "uart_rx_a";
                                function = "uart_a";
-                               bias-disable;
+                               bias-pull-up;
                        };
                };
 
@@ -540,7 +540,7 @@
                                groups = "uart_tx_b",
                                       "uart_rx_b";
                                function = "uart_b";
-                               bias-disable;
+                               bias-pull-up;
                        };
                };
 
@@ -558,7 +558,7 @@
                                groups = "uart_tx_c",
                                       "uart_rx_c";
                                function = "uart_c";
-                               bias-disable;
+                               bias-pull-up;
                        };
                };