[PATCH 1/1 v3] Termination resistor documentation

[PATCH 1/1 v3] Termination resistor documentation

[Daniel S. Trevitz]

Add documentation for how to use and setup the switchable termination
resistor support for the can-controllers.

Signed-off-by: Daniel Trevitz <dan@sstrev.com>
---
 Documentation/networking/can.rst | 33 ++++++++++++++++++++++++++++++++
 1 file changed, 33 insertions(+)

diff --git a/Documentation/networking/can.rst b/Documentation/networking/can.rst
index ebc822e605f5..90121deef217 100644
--- a/Documentation/networking/can.rst
+++ b/Documentation/networking/can.rst
@@ -1148,6 +1148,39 @@ tuning on deep embedded systems'. The author is running a MPC603e
 load without any problems ...
 
 
+Switchable Termination Resistors
+--------------------------------
+
+CAN bus requires a specific impedance across the differential pair,
+typically provided by two 120Ohm resistors on the farthest nodes of
+the bus. Some CAN controllers support activating / deactivating a
+termination resistor(s) to provide the correct impedance.
+
+Query the available resistances::
+
+    $ ip -details link show can0
+    ...
+    termination 120 [ 0, 120 ]
+
+Activate the terminating resistor::
+
+    $ ip link set dev can0 type can termination 120
+
+Deactivate the terminating resistor::
+
+    $ ip link set dev can0 type can termination 0
+
+To enable termination resistor support to a can-controller, either
+implement in the controller's struct can-priv::
+
+    termination_const
+    termination_const_cnt
+    do_set_termination
+
+or add gpio control with the device tree entries from
+Documentation/devicetree/bindings/net/can/can-controller.yaml
+
+
 The Virtual CAN Driver (vcan)
 -----------------------------
 
-- 
2.35.1

Re: [PATCH 1/1 v3] Termination resistor documentation

[Marc Kleine-Budde]

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On 07.10.2022 07:53:02, Daniel S. Trevitz wrote:
> Add documentation for how to use and setup the switchable termination
> resistor support for the can-controllers.
> 
> Signed-off-by: Daniel Trevitz <dan@sstrev.com>

Applied to linux-can/main

Thanks,
Marc

-- 
Pengutronix e.K.                 | Marc Kleine-Budde           |
Embedded Linux                   | https://www.pengutronix.de  |
Vertretung West/Dortmund         | Phone: +49-231-2826-924     |
Amtsgericht Hildesheim, HRA 2686 | Fax:   +49-5121-206917-5555 |

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