cope with I$ miss on teensy #405
Open
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
if the instruction cache is completely flushed *even before* the counter is read, under specific situations (presumably when relevant parts of show() are on different cache lines), the first bit would not be sent (but discarded), often leading to a change in colour. prevent compiler optimisation across counter reads, order the delays so that they are easier to reason about.
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Outdated suggestions cannot be applied.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.
if the instruction cache is completely flushed even before the counter is read, under specific situations (presumably when relevant parts of show() are on different cache lines), the first bit would not be sent (but discarded), often leading to a change in colour.
prevent compiler optimisation across counter reads, order the delays so that they are easier to reason about.
Thank you for creating a pull request to contribute to Adafruit's GitHub code!
Before you open the request please review the following guidelines and tips to
help it be more easily integrated:
this is supposed to fix instruction cache invalidation breaks timing on teensy4 #404
the patch was tested against version 1.1.7 (blame platformio...), but the relevant part of the teensy code seems to not have changed since then. will test with master in a bit.