This series tries to revive the work of Heiko Stuebner from 2020 On the boards that we are using (ringneck/puma-haikou) a hardware switch can set the rs485 transceiver into half or full duplex mode. In half-duplex mode the DE/RE signal of the rs485 transceiver is not connected to an RTS signal whose control is already handled in the rs485 emulation (start/stop callbacks), but rather to a gpio. And since enabling the receiver requires setting this gpio active we need to do that in em485 while receiving and disable it while sending to enable the driver mode. In full-duplex mode RE is grounded and separated from DE. Meanwhile the rx-enable gpio remains connected to the DE pin. In this case the receiver-enable gpio should be disabled to enable driver mode in parallel to the enabled receiver. This patch-series adds support for controlling the receiver mode using a gpio in em485 for half-duplex mode while allowing users to keep using the full-duplex feature if em485 is disabled. Changes in v5: - set port->rs485_re_gpio in "serial: 8250: Support separate rs485 rx-enable GPIO" - Link to v4: https://lore.kernel.org/r/20240126-dev-rx-enable-v4-0-45aaf4d96328@xxxxxxxxxxxxxxxxxxxxx Changes in v4: - define the state of rx-enable gpio when em485 is disabled - add rs485 half/full duplex support to ringneck/puma-haikou - use dev_err_probe instead of dev_err if error is -EPROBE_DEFER Changes from the 2020 submission include: - external gpio for optional receiver-enable handling - Link to v3: https://lore.kernel.org/all/20200517215610.2131618-1-heiko@xxxxxxxxx/ --- Farouk Bouabid (4): dt-bindings: serial: add binding for rs485 rx-enable state when rs485 is disabled serial: 8250: set rx-enable gpio state when rs485 is disabled arm64: dts: rockchip: rk3399-puma-haikou: add rs485 support on uart2 arm64: dts: rockchip: px30-ringneck-haikou: add rs485 support on uart5 Heiko Stuebner (2): dt-bindings: serial: Add binding for rs485 receiver enable GPIO serial: 8250: Support separate rs485 rx-enable GPIO Documentation/devicetree/bindings/serial/rs485.yaml | 9 +++++++++ arch/arm64/boot/dts/rockchip/px30-ringneck-haikou.dts | 2 ++ arch/arm64/boot/dts/rockchip/rk3399-puma-haikou.dts | 4 +++- drivers/tty/serial/8250/8250_port.c | 11 ++++++++++- drivers/tty/serial/serial_core.c | 11 +++++++++++ include/linux/serial_core.h | 2 ++ 6 files changed, 37 insertions(+), 2 deletions(-) --- base-commit: 5ebe731c2a586b379103f736cd498bcca3cf1ea9 change-id: 20240125-dev-rx-enable-d8818dbf7c28 Best regards, -- Farouk Bouabid <farouk.bouabid@xxxxxxxxxxxxxxxxxxxxx>
