In order to simplify the use of CPU counter values it is beneficial to
have monotonic increasing values within the range of the CPU counter
ticks data type, e.g. 32-bit unsigned integer. This eases the use of
CPU counter timestamps in external tools which do not know the details
of the CPU counter hardware. The CPU counter is the fastest way to get
a time on an RTEMS system.
Such a CPU counter may be also used as the timecounter. Use it on SPARC
for this purpose to simplify the clock drivers.
Update #3456.
The aim of this clock driver hook was to stop clock tick interrupts at
some late point in the exit() procedure.
The use of atexit() pulls in malloc() which pulls in errno. It is
incompatible with the intention of the
CONFIGURE_DISABLE_NEWLIB_REENTRANCY configuration option.
The exit() function must be called from thread context, so accompanied
clock tick interrupts should cause no harm. On the contrary, someone
may assume a normal operating system operation, e.g. working timeouts.
Remove the Clock_driver_support_shutdown_hardware() clock driver hook.
Close#3436.
Add rtems_counter_frequency() API function. Use it to initialize the
counter value converter via the new system initialization step
(RTEMS_SYSINIT_CPU_COUNTER). This decouples the counter implementation
and the counter converter. It avoids an unnecessary pull in of the
64-bit integer division from libgcc.
Update #3456.
