I got MCP2515 working on 250Kbps on NuttX using this configuration setting:

[*] Microchip MCP2515 CAN Bus Controller over SPI
(250000) MCP2515 bitrate
(6) MCP2515 Propagation Segment TQ
(5) MCP2515 Phase Segment 1
(4) MCP2515 Phase Segment 2
(3) MCP2515 Synchronization Jump Width
(8000000) MCP2515 on-board clock frequency
(1000000) MCP2515 SPI SCK Frequency

This timing was based on Timing Suggestions from this guy:

https://github.com/electricimp/MCP2515

• BrainDamage