On Mon, Nov 20, 2023 at 04:10:54PM +0100, Rasmus Villemoes wrote: > Some boards are capable of both rs232 and rs485, and control which > external terminals are active via a gpio-controlled mux. Allow > describing that gpio in DT so that the kernel can transparently handle > the proper setting when the uart is switched between rs232 and rs485 > modes. Crescent CY Hsieh (+cc) is in parallel trying to add an RS-422 mode bit to struct serial_rs485: https://lore.kernel.org/all/20231121095122.15948-1-crescentcy.hsieh@xxxxxxxx/ I don't know whether that makes sense at all (I had thought RS-422 is the same as RS-485 with full-duplex, i.e. SER_RS485_ENABLED plus SER_RS485_RX_DURING_TX). But if that patch gets accepted, we'd have *three* different modes: RS-232, RS-485, RS-422. A single GPIO seems insufficient to handle that. You'd need at least two GPIOs. > --- a/Documentation/devicetree/bindings/serial/rs485.yaml > +++ b/Documentation/devicetree/bindings/serial/rs485.yaml > @@ -61,6 +61,11 @@ properties: > the active state enables RX during TX. > maxItems: 1 > > + rs485-mux-gpios: > + description: GPIO pin to control muxing of the SOC signals to the RS485 > + transceiver. > + maxItems: 1 The description doesn't really add much to the name "rs485-mux-gpios". Suggestion: description: selects whether the UART is connect to an RS-232 driver (low) or an RS-485 transceiver (high) Thanks, Lukas
