It is necessary to enable the DWT using a special initialization
sequence before the CYCCNT can be enabled. See for example the
RESET_CYCLE_COUNTER in libbsp/arm/atsam/utils/utility.h.
Note that this problem only occurs if no debugger is connected. A
debugger most likely already enables the necessary module.
Since the FP area pointer is passed by reference in
_CPU_Context_Initialize_fp() the optional FP area adjustment via
_CPU_Context_Fp_start() is superfluous. It is also wrong with respect
to memory management, e.g. pointer passed to _Workspace_Free() may be
not the one returned by _Workspace_Allocate().
Close#1400.
The fatal is internal indicator is redundant since the fatal source and
error code uniquely identify a fatal error. Keep the fatal user
extension is internal parameter for backward compatibility and set it to
false always.
Update #2825.
Use _Thread_Do_dispatch() instead of _Thread_Dispatch(). Restore the
PSR[EF] state of the interrupted context via new system call
syscall_irqdis_fp in case floating-point support is enabled.
On SMP configurations, it is a fatal error to call blocking operating
system with interrupts disabled, since this prevents delivery of
inter-processor interrupts. This could lead to executing threads which
are not allowed to execute resulting in undefined behaviour.
The ARM Cortex-M port has a similar problem, since the interrupt state
is not a part of the thread context.
Update #2811.
We cannot use the MRS or MSR instructions in Thumb-1 mode. Stay in ARM
mode for the Thumb-1 targets during interrupt low-level processing.
Update #2751.
Use a processor-specific interrupt frame during context switches in case
the executing thread is longer executes on the processor and the heir
thread is about to start execution. During this period we must not use
a thread stack for interrupt processing.
Update #2809.
Use the previously unused TPIDRPRW register to get the per-CPU control
of the current processor. This avoids instructions in
GET_SELF_CPU_CONTROL which are not available in Thumb mode.
Add _CPU_Get_current_per_CPU_control() on SMP configurations. Use SPRG0
for the current per-CPU control. This reduces the code size by three
instructions and is slightly faster.
Update #2805.
The aim of this file is to encapsulate CPU port implementation details.
This helps to hide implementation details from <rtems.h> which
indirectly includes <rtems/score/cpu.h>.
The use of actual cache line max bytes and minimum required alignment
in architecture but not-BSP dependent code could be problematic
because there exists even ARM instruction set implementations
with 128 byte line length and real maximum can be quite problematic
to say. But actually supported ARM BSPs should be OK with these values.
Only use CPU_Per_CPU_control if it contains at least one filed. In GNU
C empty structures have a size of zero. In C++ structures have a
non-zero size. In case CPU_PER_CPU_CONTROL_SIZE is defined to zero,
then this structure is not used anymore.
