[hatari-devel] Many changes to MFP

[Nicolas Pomarède <npomarede@xxxxxxxxxxxx>]

Hello

although OK most of the time, the code in mfp.c had some serious 
bugs/limitations that affected a limited number of games/demos, but 
required quite a lot of rewrite to get the good results.

Some of the problems :

 - in MFP_CheckPendingInterrupts, if several interrupts happened at the 
same time, they would all be processed (instead of handling only the 
highest one) and moreover, they would be processed in reverse order (so 
timer C would be handled before timer B for example !)

 - in newcpu.c, do_specialties_interrupt was called each time 
PendingInterruptCount remained < 0, instead of calling it only once when 
all PendingInterruptFunction were processed, to start an exception only 
for the highest priority interrupt.

 - an extra delay of 4 cycles is required when the MFP's IRQ signal is 
set before it is visible to the CPU (but this delay is not always 
necessary, it depends on when the signal was set while processing the 
current cpu instruction, so this involves some kind of sub-instruction 
level when processing timers)

All in all, this required quite a lot of careful changes, as the mfp is 
a rather central part of the computer and any error can have big (bad) 
impacts.

I also moved the DSP interrupt part back in falcon/dsp.c, as it doesn't 
belong to the MFP and has no interrupt number of its own in mfp.c.

This new code should fix a few games (rasters in Super Hang On and Super 
Monaco GP, Bolo not starting) as well as a few demos (Audio Artistic 
Demo by Big Alec, Reset part in Decade Demo, ...)

I tested a lot of games / demos to avoid regression, but it's possible 
some program are not working anymore, don't hesite to test your 
favorites demos/games (especially Falcon's programs, I didn't test them 
that much).

More work is still required to handle MFP interrupt happening *during* 
the processing of an exception (Main Menu in Anomaly Demo for example). 
This is rather tricky, as it requires to emulate the IACK cycles between 
the CPU and the MFP. Hopefully I should fix this in another patch.



Nicolas