ABB semaphore protection overhaul The ABB semaphone protection logic that came with TCS211 from TI was broken in several ways: * Some semaphore-protected functions were called from Application_Initialize() context. NU_Obtain_Semaphore() called with NU_SUSPEND fails with NU_INVALID_SUSPEND in this context, but the return value wasn't checked, and NU_Release_Semaphore() would be called unconditionally at the end. The latter call would increment the semaphore count past 1, making the semaphore no longer binary and thus no longer effective for resource protection. The fix is to check the return value from NU_Obtain_Semaphore() and skip the NU_Release_Semaphore() call if the semaphore wasn't properly obtained. * Some SPI hardware manipulation was being done before entering the semaphore- protected critical section. The fix is to reorder the code: first obtain the semaphore, then do everything else. * In the corner case of L1/DSP recovery, l1_abb_power_on() would call some non-semaphore-protected ABB & SPI init functions. The fix is to skip those calls in the case of recovery. * A few additional corner cases existed, all of which are fixed by making ABB semaphore protection 100% consistent for all ABB functions and code paths. There is still one remaining problem of priority inversion: suppose a low- priority task calls an ABB function, and some medium-priority task just happens to preempt right in the middle of that semaphore-protected ABB operation. Then the high-priority SPI task is locked out for a non-deterministic time until that medium-priority task finishes its work and goes back to sleep. This priority inversion problem remains outstanding for now.

FC Tourmaline stdmodem functional configuration is equivalent to Magnetite
hybrid.  The only intentional diff from Magnetite to Tourmaline in the modem
configuration is the change of Nucleus: Magnetite uses the blob version of
Nucleus which came with TCS211-20070608, whereas Tourmaline uses the source
version of Nucleus by Comrade XVilka.  It is essentially a change from an
unknown version of Nucleus to a known one, thus it should generally be
considered an improvement - but as always with such changes, extensive
verification and testing needs to be done in order to ensure that nothing got
broken.

Aside from the one intentional change of Nucleus version, FC Tourmaline is an
entirely new firmware source tree, thus it is always possible that something
could have got broken unintentionally, particularly in rarely-tested areas of
the firmware.  Therefore, extensive testing will need to be done before we can
declare Tourmaline stdmodem as officially replacing Magnetite hybrid for stable
modem products.