Hello, I have a board with a RPi CM3 and 4 mcp2515. The mcp2515 are on "constant power" (vdd/reset not controlled by RPi/linux). On a "cold-start" (power on) things come up as expected, but if I do a soft reboot (sudo reboot) or do rmmod mcp251x && modprobe mcp251x the drivers probe fails with ENODEV every other time. (I've also tested hooking up a GPIO to reset, describing vdd/xciever regulator in devicetree so driver resets the mcp2515, but that did not help at all.) Other people seem to have similar issues and multiple different workarounds/hacks are discussed in https://github.com/raspberrypi/linux/issues/2767 According to my personal testing I can make the probing reliable just by raising MCP251X_OST_DELAY_MS [1] to 30ms which seems to be the sweet spot for me. (25ms isn't enough, while 40ms as suggested in last comment in the raspberrypi issue doesn't seem to be needed either.) This all seems related to this old commit[2] so I'm hoping the involved people can please comment on this issue. Is raising the delay this much acceptable? Is it just working around the symptom of another problem? commit ff06d611a31c4b687c7859e3c7516a38194d4d25 "can: mcp251x: Improve mcp251x_hw_reset()" Regards, Andreas Henriksson [1]: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/net/can/spi/mcp251x.c#n218 [2]: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=ff06d611a31c4b687c7859e3c7516a38194d4d25
