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Diffstat (limited to 'cpu-supplement/arm.rst')
-rw-r--r-- | cpu-supplement/arm.rst | 24 |
1 files changed, 15 insertions, 9 deletions
diff --git a/cpu-supplement/arm.rst b/cpu-supplement/arm.rst index 63aa532..b92e6d6 100644 --- a/cpu-supplement/arm.rst +++ b/cpu-supplement/arm.rst @@ -34,10 +34,10 @@ for the values. Count Leading Zeroes Instruction -------------------------------- -The ARMv5 and later has the count leading zeroes ``clz`` instruction which -could be used to speed up the find first bit operation. The use of this -instruction should significantly speed up the scheduling associated with a -thread blocking. This is currently not used. +The ARMv5 and later instruction sets have the count leading zeroes ``clz`` +instruction which could be used to speed up the find first bit operation. The +use of this instruction should significantly speed up the scheduling associated +with a thread blocking. This is currently not used. Floating Point Unit ------------------- @@ -130,7 +130,13 @@ Memory Model ============ A flat 32-bit memory model is supported. The board support package must take -care about the MMU if necessary. +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 ==================== @@ -194,13 +200,13 @@ actions: Symmetric Multiprocessing ========================= -SMP is supported on ARMv7-A. Available platforms are +SMP is supported on ARMv7-A. Available platforms are: -- Altera Cyclone V, +- Altera Cyclone V -- NXP i.MX 7, and +- NXP i.MX 7 -- Xilinx Zynq. +- Xilinx Zynq Thread-Local Storage ==================== |