The SPARC ABI is a bit special with respect to the floating point context.
The complete floating point context is volatile. Thus from an ABI point
of view nothing needs to be saved and restored during a context switch.
Instead the floating point context must be saved and restored during
interrupt processing. Historically the deferred floating point switch is
used for SPARC and the complete floating point context is saved and
restored during a context switch to the new floating point unit owner.
This is a bit dangerous since post-switch actions (e.g. signal handlers)
and context switch extensions may silently corrupt the floating point
context. The floating point unit is disabled for interrupt handlers.
Thus in case an interrupt handler uses the floating point unit then this
will result in a trap.
On SMP configurations the deferred floating point switch is not
supported in principle. So use here a safe floating point support. Safe
means that the volatile floating point context is saved and restored
around a thread dispatch issued during interrupt processing. Thus
post-switch actions and context switch extensions may safely use the
floating point unit.
Update #2270.
Store the floating-point unit property in the thread control block
regardless of the CPU_HARDWARE_FP and CPU_SOFTWARE_FP settings. Make
sure the floating-point unit is only enabled for the corresponding
multilibs. This helps targets which have a volatile only floating point
context like SPARC for example.
Define CONTEXT_FP_SIZE to zero in case hardware and software floating
point support is disabled. The problem is that empty structures have a
different size in C and C++. In C++ they have a non-zero size leading
to an overestimate of the workspace size.
With the introduction of fine grained locking there is no longer a
one-to-one connection between the Giant lock nest level and the thread
dispatch disable level.
It is wrong to restore the floating point context here. The
_Context_Switch() ends up in _Thread_Handler() which will call
_Thread_Restore_fp(). In _Thread_Do_dispatch() the FP restore is after
the context switch.
In case the zlib compression was used, then the librtemscpu.a depended
on libz.a. To avoid a GCC patch or complicated link flags move the
JFFS2 support into a separate library to use a simple "-ljffs2 -lz" to
link the executable.
basic VGA driver can be enabled during configure phase by exporting variable
USE_VGA=1 so that it is available in configure environment
cirrus driver is enabled the same way by exporting variable
USE_CIRRUS_GD5446=1
driver is not initialized by default
initialization is possible through multiboot command line option or
through the string variable (see fb_default_mode.h) set in user's module
allowing the driver to evaluate this variable after the two
modules are linked together
This BSP in intended to run on the simulator that should be built
from RSB. When building RTEMS for Epiphany --disable-networking must
be provided part of the configure command.
