[Buildroot] Use the CAN0 device on beaglebone black

[Robert Nelson]

On Fri, May 14, 2021 at 2:37 AM Andy Bergh <allmyaddmin at gmail.com> wrote:
>
> Hi,
>
> How can I use the CAN0 device with a Buildroot image?
>
> I have a Beaglebone black rev C and have built an image using Buildroot. I used the standard beaglebone_defconfig and installed can-utils as well as iproute2.
>
> My understanding is that the i2c2 pins should be reconfigured to be able to use the CAN0 device. In order to keep things simple (and avoid overlays) I edit the "am335x-bone-common.dtsi" file in two ways.
>
> 1) Comment out the i2c2 and insert the CAN0 pin setup:
>
> //    i2c2_pins: pinmux_i2c2_pins {
> //        pinctrl-single,pins = <
> //            0x178 (PIN_INPUT_PULLUP | MUX_MODE3)    /* uart1_ctsn.i2c2_sda */
> //            0x17c (PIN_INPUT_PULLUP | MUX_MODE3)    /* uart1_rtsn.i2c2_scl */
> //        >;
> //    };
>
> dcan0_pins: pinmux_dcan0_pins {
>         pinctrl-single,pins = <
>             0x178 (PIN_OUTPUT_PULLUP | MUX_MODE2)  /* P9.20 (0x178), ddcan0_tx */
>             0x17c (PIN_INPUT_PULLUP | MUX_MODE2)   /* P9.19 (0x17c), ddcan0_rx */
>         >;
>     };
>
> 2) Replace i2c2 with
> &dcan0 {
>     #address-cells = <1>;
>     #size-cells = <1>;
>     status = "okay";
>     pinctrl-names = "default";
>     pinctrl-0 = <&dcan0_pins>;
>
> };
>
> Once I log in I can not get any CAN device going anywhere:
> # ifup can0
> Cannot find device "can0"
> # ifconfig can0 up
> ifconfig: SIOCGIFFLAGS: No such device
>
> And looking at the available networks
>
> # ls -al /sys/class/net/
> total 0
> drwxr-xr-x    2 root     root             0 Jan  1 00:00 .
> drwxr-xr-x   43 root     root             0 Jan  1 00:00 ..
> lrwxrwxrwx    1 root     root             0 Jan  1 00:00 eth0 -> ../../devices/platform/ocp/4a100000.ethernet/net/eth0
> lrwxrwxrwx    1 root     root             0 Jan  1 00:00 lo -> ../../devices/virtual/net/lo
> lrwxrwxrwx    1 root     root             0 Jan  1 00:02 sit0 -> ../../devices/virtual/net/sit0
>
> I have exhausted all resources and am truly stuck. Any information which may help will be greatly appreciated.

Double check your kernel config:

CONFIG_CAN_C_CAN=y
CONFIG_CAN_C_CAN_PLATFORM=y

Regards,

-- 
Robert Nelson
https://rcn-ee.com/