stm32f4xx: handle usart overrun error #3844
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Similarly to the stm32f303xc usart driver, the overrun error handler clears the error flag, sets the rx_status back to Idle and notifies the client. In this case, the ongoing DMA transfer is also aborted. Furthermore, the tx complete handler is now executed only if the TC flag is actually set, to avoid running it upon an error interrupt event. This handler avoids the usart driver to hang indefinitely after an overrun error occurs.
bradjc
approved these changes
Feb 11, 2024
|
I've been thinking about your question, and I'm not sure I have a great answer. I think in general virtualizing any resource is hard, and it is complicated to determine what to expose and what not to expose. I can't actually remember if just restarting the error on behalf of the user is intentional, or just an implementation artifact. |
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Pull Request Overview
This pull request adds an overrun error handler to the stm32f4xx usart driver. This avoids the usart driver to hang indefinitely upon an overrun error event.
Testing Strategy
Tested with a nucelo-f439zi by using the process console with default parameters. I noticed that after pressing the DEL key, the console was not responding anymore. This was due to an overrun error occurred after sending multiple characters to the console as the DEL key is an escape sequence. I could reproduce the same behavior by pasting a multiple characters string into the console (e.g. "hello123").
I am still not sure why the overrun occurs in this scenario, it would require further investigation. However, with the addition of the error handler the corresponding ReceiveClient, the MuxUart in this case, is notified and a new read is started. The effect on the process console is that some characters get skipped during overrun error events.
I could run other tests if anyone could point them out.
TODO or Help Wanted
I think a review is necessary since I am not yet very familiar with Tock. In particular, one thing I find odd is that the error gets notified to the MuxUart which however does not propagate it to the underlying process_console. This seems to happen because the read is not yet completed, so the call to
device.received_buffer()is skipped and a new read is started. Is this a wanted behavior? Are there any other implications I am not seeing?Documentation Updated
Formatting
make prepush.