This change enables interrupts within timer callbacks, making it
possible to load pages to MMU while handling a timer underflow. The call
to TLB_LoadPTEH() has been moved directly into the VBR handler to avoid
jumping to ILRAM for a short call on SH4.
The TMU and ETMU handlers have been changed to callback through a new
function gint_inth_callback() that saves the user bank and a few
registers, then invokes the callback with interrupts enabled and in user
bank; until now, callbacks were invoked with interrupts disabled and in
kernel bank. Note that IMASK is still set so a callback can only be
interrupted by a high-priority interrupt.
A timer_wait() function has also been added to simplify tests that
involve timers. Finally, the priority level of the TMU0 underflow
interrupt has been set to 13 (as per the comments) instead of 7.
This version is the first stable version that handles TLB misses
transparently for large add-ins. It is suitable for every gint
application.
This is an obvious requirement for the interrupt routine, which was
forgotten and only surfaced when I used a timer callback started with
multiplications in an innocent add-in. r0..r7 are saved automatically,
which leaves pr, gbr, mach et macl susceptible to corruption by the
interrupt handler.
This change introduces exception handlers that default to a fatal error
with an on-screen description of the exception and some debugging
information.
It also adds the dprint() function as a definitely-needed helper and
removes bootlog_unmapped() by using the exception handler for the fatal
error display. (Also printf() is now required in all gint add-ins; this
is sad, but space is not as much of a constraint as debugging.)
Finally, the exception handler is used to handle an interrupt which is
an exception in practice, the DMA address error. On fx-CG 50, additional
DMA-related information is displayed on the screen. This is left out on
fx-9860G as there is not enough space.
