| Message ID | 20231011145602.3619616-2-manikanta.guntupalli@amd.com |
|---|---|
| State | New |
| Headers | show |
| Series | [V2,1/2] dt-bindings: Add optional gpio property to uartps node to support rs485 | expand |
Manikanta Guntupalli wrote on 2023-10-11 16:56: > Add optional gpio property to uartps node and reference to rs485.yaml > > On Xilinx/AMD Kria SOM KD240 board rs485 connects via TI ISOW1432 > Transceiver device, where one GPIO is used for driving DE/RE signals. > With rs485 half duplex configuration, DE and RE shorts to each other, s/shorts/are connected > and at a time, any node acts as either a driver or a receiver. > > Here, > DE - Driver enable. If pin is floating, driver is disabled. > RE - Receiver enable. If pin is floating, receiver buffer is disabled. Please use DE and /RE to indicate DE is active high and /RE is active low. > xlnx,phy-ctrl-gpios is optional property, because it is not required > for uart console node. How about introducing an rs485 generic gpios property instead of xlnx private one? See also rs485-term-gpios and rs485-rx-during-tx-gpios. Also note that every kernel driver expects to use RTS for this purpose. So why not give this driver the option to choose a gpio instead of its native RTS? And from there on use the rts route? What if someone wants to use normal (non-rs485) RTS on a GPIO instead of the native pin? @Rob Herring I am curious to know how the rs485 maintainers look at this. Maarten
On Thu, Oct 12, 2023 at 08:35:59PM +0200, m.brock@vanmierlo.com wrote: > Manikanta Guntupalli wrote on 2023-10-11 16:56: > > Add optional gpio property to uartps node and reference to rs485.yaml > > > > On Xilinx/AMD Kria SOM KD240 board rs485 connects via TI ISOW1432 > > Transceiver device, where one GPIO is used for driving DE/RE signals. > > With rs485 half duplex configuration, DE and RE shorts to each other, > > s/shorts/are connected > > > and at a time, any node acts as either a driver or a receiver. > > > > Here, > > DE - Driver enable. If pin is floating, driver is disabled. > > RE - Receiver enable. If pin is floating, receiver buffer is disabled. > > Please use DE and /RE to indicate DE is active high and /RE is active low. > > > xlnx,phy-ctrl-gpios is optional property, because it is not required > > for uart console node. > > How about introducing an rs485 generic gpios property instead of xlnx > private one? See also rs485-term-gpios and rs485-rx-during-tx-gpios. > > Also note that every kernel driver expects to use RTS for this purpose. > So why not give this driver the option to choose a gpio instead of its > native RTS? And from there on use the rts route? > What if someone wants to use normal (non-rs485) RTS on a GPIO instead > of the native pin? > > @Rob Herring > I am curious to know how the rs485 maintainers look at this. Ask them. We already have 'rts-gpios'. If that's what's always used, then perhaps we should use that in the RS485 case too? Rob
Rob Herring wrote on 2023-10-12 22:51: >> How about introducing an rs485 generic gpios property instead of xlnx >> private one? See also rs485-term-gpios and rs485-rx-during-tx-gpios. >> >> Also note that every kernel driver expects to use RTS for this >> purpose. >> So why not give this driver the option to choose a gpio instead of its >> native RTS? And from there on use the rts route? >> What if someone wants to use normal (non-rs485) RTS on a GPIO instead >> of the native pin? >> >> @Rob Herring >> I am curious to know how the rs485 maintainers look at this. > > Ask them. Funny, your name is the only one listed under the maintainers in Documentation/devicetree/bindings/serial/rs485.yaml And there is no mention of (RS-)485 in MAINTAINERS. > We already have 'rts-gpios'. If that's what's always used, then perhaps > we should use that in the RS485 case too? > > Rob Sounds like a good idea. Maarten
diff --git a/Documentation/devicetree/bindings/serial/cdns,uart.yaml b/Documentation/devicetree/bindings/serial/cdns,uart.yaml index a8b323d7bf94..cf8ef55ba210 100644 --- a/Documentation/devicetree/bindings/serial/cdns,uart.yaml +++ b/Documentation/devicetree/bindings/serial/cdns,uart.yaml @@ -46,6 +46,11 @@ properties: power-domains: maxItems: 1 + xlnx,phy-ctrl-gpios: + description: Optional GPIO to control transmit/receive on RS485 phy + in halfduplex mode. + maxItems: 1 + required: - compatible - reg @@ -55,6 +60,7 @@ required: allOf: - $ref: serial.yaml# + - $ref: rs485.yaml# - if: properties: compatible:
Add optional gpio property to uartps node and reference to rs485.yaml On Xilinx/AMD Kria SOM KD240 board rs485 connects via TI ISOW1432 Transceiver device, where one GPIO is used for driving DE/RE signals. With rs485 half duplex configuration, DE and RE shorts to each other, and at a time, any node acts as either a driver or a receiver. Here, DE - Driver enable. If pin is floating, driver is disabled. RE - Receiver enable. If pin is floating, receiver buffer is disabled. For more deatils, please find below link which contains Transceiver device(ISOW1432) datasheet https://www.ti.com/lit/ds/symlink/isow1432.pdf?ts=1682607122706&ref_url=https%253A%252F%252Fwww.ti.com%252Fproduct%252FISOW1432%252Fpart-details%252FISOW1432DFMR%253FkeyMatch%253DISOW1432DFMR%2526tisearch%253Dsearch-everything%2526usecase%253DOPN xlnx,phy-ctrl-gpios is optional property, because it is not required for uart console node. Signed-off-by: Manikanta Guntupalli <manikanta.guntupalli@amd.com> --- Changes for V2: Modify optional gpio name to xlnx,phy-ctrl-gpios. Update commit description. --- Documentation/devicetree/bindings/serial/cdns,uart.yaml | 6 ++++++ 1 file changed, 6 insertions(+)