arm64: dts: amlogic: axg: 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/20250329185855.854186-7-martin.blumenstingl@googlemail.com
Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>

diff --git a/arch/arm64/boot/dts/amlogic/meson-axg.dtsi b/arch/arm64/boot/dts/amlogic/meson-axg.dtsi
index a6924d246bb1e1721a1a9a3a8285f98c003c2640..2df143aa77ce3ca4f101ffe0c6ed83c6a3bc52c5 100644 (file)
--- a/arch/arm64/boot/dts/amlogic/meson-axg.dtsi
+++ b/arch/arm64/boot/dts/amlogic/meson-axg.dtsi
@@ -1164,7 +1164,7 @@
                                                groups = "uart_tx_a",
                                                         "uart_rx_a";
                                                function = "uart_a";
-                                               bias-disable;
+                                               bias-pull-up;
                                        };
                                };
 
@@ -1182,7 +1182,7 @@
                                                groups = "uart_tx_b_x",
                                                         "uart_rx_b_x";
                                                function = "uart_b";
-                                               bias-disable;
+                                               bias-pull-up;
                                        };
                                };
 
@@ -1200,7 +1200,7 @@
                                                groups = "uart_tx_b_z",
                                                         "uart_rx_b_z";
                                                function = "uart_b";
-                                               bias-disable;
+                                               bias-pull-up;
                                        };
                                };
 
@@ -1218,7 +1218,7 @@
                                                groups = "uart_ao_tx_b_z",
                                                         "uart_ao_rx_b_z";
                                                function = "uart_ao_b_z";
-                                               bias-disable;
+                                               bias-pull-up;
                                        };
                                };
 
@@ -1654,7 +1654,7 @@
                                                groups = "uart_ao_tx_a",
                                                         "uart_ao_rx_a";
                                                function = "uart_ao_a";
-                                               bias-disable;
+                                               bias-pull-up;
                                        };
                                };
 
@@ -1672,7 +1672,7 @@
                                                groups = "uart_ao_tx_b",
                                                         "uart_ao_rx_b";
                                                function = "uart_ao_b";
-                                               bias-disable;
+                                               bias-pull-up;
                                        };
                                };