This commit refactors the FPU handling code on the Xtensa port of Amazon SMP
FreeRTOS in the following ways:
Auto-pinning via XT_RTOS_CP_EXC_HOOK
------------------------------------
The "_xt_coproc_exc" exception would previously automatically pin a task that
uses the FPU to the current core (to ensure that we can lazy save the task's FPU
context). However, this would mean that "xtensa_vectors.S" would need to be
OS-aware (to read the task's TCB structure).
This is now refactored so that "_xt_coproc_exc" calls a CP exception hook
function ("XT_RTOS_CP_EXC_HOOK") implemented in "portasm.S", thus allowing
"xtensa_vectors.S" to remain OS agnostic.
Using macros to acquire owner spinlock
--------------------------------------
The taking and relasing of the "_xt_coproc_owner_sa_lock" is now mostly
abstracted as the "spinlock_take" and "spinlock_release" macro. As a result,
"_xt_coproc_release" and "_xt_coproc_exc" are refactored so that:
- They are closer to their upstream (original) versions
- The spinlock is only taken when building for multicore
- The spinlock held region is shortened (now only protects the instructions
that access the "_xt_coproc_owner_sa" array
Other Changes
-------------
- Updated placing and comments of various "offset_..." constants used by
portasm.S
- Update description of "get_cpsa_from_tcb" assembly macro
- Tidied up some typos in the ".S" files
This commit fixes the following FPU/Coprocessor bugs in the Xtensa port of
Amazon SMP FreeRTOS:
- vPortCleanUpCoprocArea() does not calculate the correct pointer to the
task's CPSA (located on the task's stack). This can result in
- _xt_coproc_release() not releasing the task's CP ownership
- The next coprocessor exception will write the current CP owner (i.e., the
deleted task's CPSA) leading to memory corruption
- _xt_coproc_release() writes xCoreID instead of 0 when clearing a CP owner.
This results in the next CP exception trying to load the CP owner's CPSA at
the address of "xCoreID", leading to a double exception.
This commit copies over ESP-IDF Xtensa portable files to the
FreeRTOS-Kernel-SMP directory. No changes were made, this commit
only copies the portable source files.
Notes:
- This commit WILL NOT compile
- Some SPDX header dates were updated to pass pre-commit check
