darrylring opened a new pull request, #21020: URL: https://github.com/apache/nuttx/pull/21020
## Summary Add support for the CANIOC_SET_NART ioctl which controls whether or not the FDCAN peripheral automatically resends frames that lose arbitration or hit bus errors. On the STM32H5's FDCAN peripheral (M_CAN) this is DAR (disable automatic retry) mode. Frames dropped in DAR mode don't trigger TC (transmit complete) or TCF (transmit cancellation finished) interrupts, but they do empty the TX FIFO and trigger TFE (transmit FIFO empty). Currently `can_txdone` is only called on TC interrupts, so the transmit queue fills up and eventually `write` blocks. They also don't set TXBTO (transmission occurred) so the existing logic still wouldn't work. Instead, keep track of busy transmit buffers and ensure they are marked done when transmit is complete, manually cancelled, or automatically cancelled. ## Impact The existing transmit completion handling has been modified: 1. Transmit completion is now tracked by the driver instead of relying on the TXBTO register. 2. Interrupts are enabled on all transmit buffers on each send. 3. Transmit complete interrupt handler runs for TFE, but does not enable error interrupts on TFE only. 4. `fdcan_txready` returns false if a buffer is still in `txbusy` because hardware can free a buffer before its completion. 5. `fdcan_txempty` only returns true if `txbusy == 0` which (due to the previous note) may mean slightly more time before reporting empty (actual completion, not reported completion). ## Testing ### The basic functionality Sending a frame on an empty bus (no ACK) - before <img width="1024" height="600" alt="image" src="https://github.com/user-attachments/assets/96bdffd6-9d01-4c96-944a-632c51afeb67"; /> Sending a frame on an empty bus (no ACK) - after <img width="1024" height="600" alt="image" src="https://github.com/user-attachments/assets/9734cde1-d26a-4694-8431-664d8c31cbe0"; /> ### Stress testing A simple NSH app sends frames as quickly as possible with and without automatic resends and measure how long `write` takes to run. A CAN-USB adapter is used to record the traffic and also to send frames to cause the board to lose arbitration periodically. The goal here is to ensure that `write` never blocks, frames don't arrive out of order, and `close` never hangs. Cases: * A: send 100,000 frames, receive with candump, automatic resend ON * B: send 100,000 frames, receive with candump, cangen sending higher priority traffic, automatic resend ON * B: send 100,000 frames, receive with candump, cangen sending higher priority traffic, automatic resend OFF [candump_logs.zip](https://github.com/user-attachments/files/33982689/candump_logs.zip) -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected]
