Fix core frequency in config.txt to repair UART console #32
Conversation
This file contains 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 console becomes garbled during boot, shortly after the baud rate change and the trusted firmware boot. On Raspberry Pi 3, the mini UART clock is linked to the VPU core clock, so that when the core clock frequency changes, the UART baud rate will also change (see [1]). Fix the core frequency to 250 MHz to repair the UART console. [1]: https://www.raspberrypi.org/documentation/configuration/uart.md Signed-off-by: Vincent Stehlé <vincent.stehle@arm.com>
|
This helps on FreeBSD to keep serial console on a 3B+. Thank you! |
|
I don't think we want to enable that unconditionally because this will indeed result in loss of performance for people who don't care about the UART console and, ideally, it should be the OS job to provide a UART driver that handles VPU frequency changes. What we can do then is add the following section in |
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
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Outdated suggestions cannot be applied.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.
I propose that we fix the core frequency to 250 MHz to repair the UART console.
Arguably, we might be losing a bit of performance here, but the UART console is so useful for debug and headless operation that I think this is well worth it. Don't hesitate to let me know if you disagree.
Best regards,
Vincent.