arm64: dts: amlogic: g12: 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/20250329185855.854186-6-martin.blumenstingl@googlemail.com
Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>

diff --git a/arch/arm64/boot/dts/amlogic/meson-g12-common.dtsi b/arch/arm64/boot/dts/amlogic/meson-g12-common.dtsi
index ab2b3f15ef19463b0baa17fdee0c0952beca2ca4..12e8daaa1c9b842241b954d188b501dcd3d0db0e 100644 (file)
--- a/arch/arm64/boot/dts/amlogic/meson-g12-common.dtsi
+++ b/arch/arm64/boot/dts/amlogic/meson-g12-common.dtsi
@@ -1503,7 +1503,7 @@
                                                        groups = "uart_a_tx",
                                                                 "uart_a_rx";
                                                        function = "uart_a";
-                                                       bias-disable;
+                                                       bias-pull-up;
                                                };
                                        };
 
@@ -1521,7 +1521,7 @@
                                                        groups = "uart_b_tx",
                                                                 "uart_b_rx";
                                                        function = "uart_b";
-                                                       bias-disable;
+                                                       bias-pull-up;
                                                };
                                        };
 
@@ -1918,7 +1918,7 @@
                                                groups = "uart_ao_a_tx",
                                                         "uart_ao_a_rx";
                                                function = "uart_ao_a";
-                                               bias-disable;
+                                               bias-pull-up;
                                        };
                                };
 
@@ -1936,7 +1936,7 @@
                                                groups = "uart_ao_b_tx_2",
                                                         "uart_ao_b_rx_3";
                                                function = "uart_ao_b";
-                                               bias-disable;
+                                               bias-pull-up;
                                        };
                                };
 
@@ -1945,7 +1945,7 @@
                                                groups = "uart_ao_b_tx_8",
                                                         "uart_ao_b_rx_9";
                                                function = "uart_ao_b";
-                                               bias-disable;
+                                               bias-pull-up;
                                        };
                                };