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 driver/receiver mode using rts-gpios. Changes in v6: - "rts-gpios" property is used instead of implementing "rs485-rx-enable-gpios" - "rs485-rx-enable-inactive-when-rs485-disabled" property is no longer implemented, since rts-gpios is already controlled outside of the em485 context - Link to v5: https://lore.kernel.org/r/20240126-dev-rx-enable-v5-0-5d934eda05ca@xxxxxxxxxxxxxxxxxxxxx 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 (2): arm64: dts: rockchip: rk3399-puma-haikou: add rs485 support on uart2 arm64: dts: rockchip: px30-ringneck-haikou: add rs485 support on uart5 arch/arm64/boot/dts/rockchip/px30-ringneck-haikou.dts | 1 + arch/arm64/boot/dts/rockchip/rk3399-puma-haikou.dts | 3 ++- 2 files changed, 3 insertions(+), 1 deletion(-) --- base-commit: 5ebe731c2a586b379103f736cd498bcca3cf1ea9 change-id: 20240125-dev-rx-enable-d8818dbf7c28 Best regards, -- Farouk Bouabid <farouk.bouabid@xxxxxxxxxxxxxxxxxxxxx>
