From: "Daniel S. Trevitz" <dan@sstrev.com>
To: linux-can@vger.kernel.org
Cc: Marc Kleine-Budde <mkl@pengutronix.de>,
Daniel Trevitz <daniel.trevitz@wika.com>,
Ryan Edwards <ryan.edwards@gmail.com>
Subject: [PATCH 1/1 v2] Termination resistor documentation
Date: Fri, 07 Oct 2022 06:45:20 -0400 [thread overview]
Message-ID: <2498535.ElGaqSPkdT@daniel6430> (raw)
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 | 30 ++++++++++++++++++++++++++++++
1 file changed, 30 insertions(+)
diff --git a/Documentation/networking/can.rst b/Documentation/networking/can.rst
index ebc822e605f5..bb39cfa4c502 100644
--- a/Documentation/networking/can.rst
+++ b/Documentation/networking/can.rst
@@ -1148,6 +1148,36 @@ 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
reply other threads:[~2022-10-07 10:45 UTC|newest]
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