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| author | Kinsey Moore <kinsey.moore@oarcorp.com> | 2022-03-04 13:47:40 -0600 |
|---|---|---|
| committer | Joel Sherrill <joel@rtems.org> | 2022-03-25 10:17:15 -0500 |
| commit | df8261a46e9614f92023bb575fad7873b9d77302 (patch) | |
| tree | 7a40be11f6a36d1ff5248d28a393e30e1355285e /cpu-supplement/arm.rst | |
| parent | eng/tester.rst: Reference User Manual for rtems-test (diff) | |
| download | rtems-docs-df8261a46e9614f92023bb575fad7873b9d77302.tar.bz2 | |
cpu-supplement: Add note about device memory
Add information about restricted use of device memory for ARM and
AArch64.
Diffstat (limited to '')
| -rw-r--r-- | cpu-supplement/arm.rst | 6 |
1 files changed, 6 insertions, 0 deletions
diff --git a/cpu-supplement/arm.rst b/cpu-supplement/arm.rst index ac9e8c6..b92e6d6 100644 --- a/cpu-supplement/arm.rst +++ b/cpu-supplement/arm.rst @@ -132,6 +132,12 @@ Memory Model A flat 32-bit memory model is supported. The board support package must take care of initializing the MMU if necessary. +Note that architecture variants which support unaligned accesses must not use +memcpy() or memset() on device memory as those functions are hand-optimized and +will take advantage of unaligned accesses where available. *As per ARM* +(https://developer.arm.com/documentation/ddi0406/c/Application-Level-Architecture/Application-Level-Memory-Model/Alignment-support/Unaligned-data-access-restrictions-in-ARMv7-and-ARMv6), +unaligned accesses are not permitted for device memory. + Interrupt Processing ==================== |