[patches][picolibc][aarch64] Initialize SME #703
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
amilendra
force-pushed
the
picolib-sme-initialization
branch
from
c56649d to
76d6da9
Compare
These two patches add the following needed for SME support in picolibc 1. If SME or SME2 is enabled at EL3, 1.1 Clear TPIDR2_EL0 [1] The value of TPIDR2_EL0 resets to an architecturally UNKNOWN value at warm reset. This means we need to clear it manually at startup. 1.2 Initialise SME Streaming SVE Vector length to 2048 bits Initialize the SME control register SMCR_EL3 [2] to set the effective streaming SVE vector length to the maximum supported value of 2048 bits. 2. Add implementation of the __aarch64_sme_accessible compiler-rt relies on the the __aarch64_sme_accessible support function to emit SME ABI support routines calls [3]. __aarch64_sme_accessible returns non-zero when SME support is enabled in the underlying hardware. [1] https://developer.arm.com/documentation/ddi0601/2025-09/AArch64-Registers/TPIDR2-EL0--EL0-Read-Write-Software-Thread-ID-Register-2?lang=en [2] https://developer.arm.com/documentation/ddi0601/2025-09/AArch64-Registers/SMCR-EL3--SME-Control-Register--EL3-?lang=en [3] llvm/llvm-project@2b05fa8
amilendra
force-pushed
the
picolib-sme-initialization
branch
from
76d6da9 to
f99c303
Compare
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Outdated suggestions cannot be applied.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.
These two patches add the following needed for SME support in picolibc
1.1 Clear TPIDR2_EL0 [1]
The value of TPIDR2_EL0 resets to an architecturally UNKNOWN value at warm reset. This means we need to clear it manually at startup.
1.2 Initialise SME Streaming SVE Vector length to 2048 bits Initialize the SME control register SMCR_EL3 [2] to set the effective streaming SVE vector length to the maximum supported value of 2048 bits.
compiler-rt relies on the the __aarch64_sme_accessible support function to emit SME ABI support routines calls [3]. __aarch64_sme_accessible returns non-zero when SME support is enabled in the underlying hardware.
[1] https://developer.arm.com/documentation/ddi0601/2025-09/AArch64-Registers/TPIDR2-EL0--EL0-Read-Write-Software-Thread-ID-Register-2?lang=en
[2] https://developer.arm.com/documentation/ddi0601/2025-09/AArch64-Registers/SMCR-EL3--SME-Control-Register--EL3-?lang=en
[3] llvm/llvm-project@2b05fa8