ot_uart: default to reporting idle in the unimplemented VAL register
#169
Conversation
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
The UART's `VAL` register is currently not implemented, but since we assume that the UART is always reporting `STATUS.RXIDLE`, it makes sense that the `VAL.RX` field should always report sampling idle (high) bits instead of 0. This will help with booting ROM_EXT, which detects an incoming break condition on the UART via the VAL regsiter to determine when to enter Rescue mode via the Rescue 1.0 mechanism. Signed-off-by: Alex Jones <alex.jones@lowrisc.org>
AlexJones0
requested review from
jwnrt,
loiclefort,
rivos-eblot and
ziuziakowska
rivos-eblot
approved these changes
Sep 3, 2025
jwnrt
approved these changes
Sep 3, 2025
loiclefort
approved these changes
Sep 3, 2025
This was referenced Sep 17, 2025
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
4 participants
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
The UART's
VALregister is currently not implemented, but since we assume that the UART is always reportingSTATUS.RXIDLE, it makes sense that theVAL.RXfield should always report sampling idle (high) bits instead of 0.This will help with Earlgrey's ROM_EXT, which detects an incoming break condition on the UART via the VAL regsiter to determine when to enter Rescue mode via the Rescue 1.0 mechanism.