On 06.10.2022 15:27:50, 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@xxxxxxxxxx> > --- > 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: You need double :: followed by a newline to mark as code. > + $ ip -details link show can0 > + ... > + termination 120 [ 0, 120 The closing ] is missing, please add it, even if the current ip command doesn't print it. I just noticed it got lost in a cleanup patch in iproute2. > + > + - Activate the terminating resistor: same here > + $ ip link set dev can0 type can termination 120 > + > + - Deactivate the terminating resistor: same here > + $ 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) > ----------------------------- 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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