CVS commit: src/sys/arch/arm/include

["Nick Hudson" <skrll%netbsd.org@localhost>]

Module Name:    src
Committed By:   skrll
Date:           Fri Jun  5 08:03:38 UTC 2026

Modified Files:
        src/sys/arch/arm/include: cpufunc.h

Log Message:
arm: relax coherent DMA ordering barriers from DSB to DMB

Use DMB instead of DSB for the ARM coherent DMA ordering macros dma_*_*()

The previous definitions used DSB, which enforces completion semantics and
is heavier than needed for coherent device DMA ordering. DMB provides ordering
of memory operations without requiring full completion, making it the
appropriate barrier for these coherent-only CPU/device DMA paths.

Tested on Fusion VM, Orion O6, and Thunderx.

There is an approximate 1% performance improvement for the Fusion VM, but
less for Orion O6 and Thunderx.


To generate a diff of this commit:
cvs rdiff -u -r1.94 -r1.95 src/sys/arch/arm/include/cpufunc.h

Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.