Fix STM32 USB PMA access at O3#67
Open
ataffanel wants to merge 1 commit into
Open
Conversation
The STM32 USB packet memory area must be accessed as volatile 16-bit words. With the current GCC at -O3, the old plain uint16_t pointer lets the compiler combine descriptor writes into 32-bit stores, corrupting CDC descriptors during enumeration. Use volatile halfword PMA accesses and copy odd-length transfers byte-safely so descriptor buffers are not read or written past their requested lengths. Keep the default optimized build while allowing diagnostics with OPT overrides.
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
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
1 participant
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Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be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 STM32 USB packet memory area must be accessed as volatile 16-bit words. With the current GCC at -O3, the old plain uint16_t pointer lets the compiler combine descriptor writes into 32-bit stores, corrupting CDC descriptors during enumeration.
Use volatile halfword PMA accesses and copy odd-length transfers byte-safely so descriptor buffers are not read or written past their requested lengths. Keep the default optimized build while allowing diagnostics with OPT overrides.