FreeCalypso > hg > fc-tourmaline
view bwsplash/README @ 220:0ed36de51973
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.
| author | Mychaela Falconia <falcon@freecalypso.org> |
|---|---|
| date | Mon, 26 Apr 2021 20:55:25 +0000 |
| parents | a963d8cd8682 |
| children |
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When TI's original version of small B&W UI firmware boots or shuts down, the splash screen it displays consists of a 56x38 pixel B&W TI logo centered in the middle of the LCD. (Back when this code was owned by Condat rather than TI, this splash screen was an animated Condat logo of approximately the same size - it is still present in the code, conditioned out.) Because we are FreeCalypso and not TI or Condat, we need our own logo or at least our own splash screen to replace those other company logos. A bona fide FreeCalypso logo does not exist yet as of this writing (2021-03), and while we (Falconia family that owns FC) do have some logo ideas in the works, the 96x64 pixel B&W (1bpp) framebuffer in the FreeCalypso Lite config is far too limited compared to other media - hence we are currently going for a simple splash screen that merely consists of the words "FreeCalypso Lite". The current version of our minimal-effort splash screen is 80x30 pixels, to be centered in the middle of the 96x64 pixel LCD. The bitmap drawing is given in bwsplash.pbm, which is a Plain PBM file, making the pixel image directly viewable and editable in vi. The tools in this directory compile it into hex bytes for inclusion in C source, and the finished artifact goes into src/ui/bmi/mmiIcons.c, fc_splash_screen_smallbw[] char array. The coordinates for positioning this bitmap within the full 96x64 pixel framebuffer are given in src/ui/bmi/mmiResources.h - look for WELCOME_ANI_POS_X and WELCOME_ANI_POS_Y definitions. The present splash screen is strictly a minimal-effort job with absolutely no quality claims of any kind. If someone is more graphically talented than I am, or has more time to invest into drawing a prettier splash screen, suggestions for improvement are always welcome.