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dolphin/docs/DSP/free_dsp_rom/dsp_rom.ds
Pierre Bourdon 9a404ca6d4 Ship by default a free DSP ROM that can handle most games with LLE 
At the end of July 2011, LM published a free DSP ROM that works with games
using the Zelda UCode. His ROM only has the code to handle UCode loading and a
few utility functions, the rest is missing. This includes the four large sound
mixing functions used by the AX UCode and the DROM containing coefficients used
for polyphase resampling in AX.

This is an improved, updated version of this ROM, which changes the following:

- We now have a free DROM that works for polyphase resampling by "emulating"
  linear interpolation. The coefficients contained in the DROM are normally a
  list of { c1, c2, c3, c4 } which are used to interpolate a sample value from
  four previous samples:
    out_sample = prev1 * c1 + prev2 * c2 + prev3 * c3 + prev4 * c4

  The coefficients are chosen depending on the fractional part of the current
  position (basically, our position between the previous and the next sample).
  We can use this fact to generate (c1, c2, c3, c4) for each possible
  fractional part so that:
    out_sample = prev3 * curr_pos + prev4 * (1 - curr_pos)

  Which is the formula for linear interpolation between prev3 and prev4. Linear
  interpolation is not as good as polyphase resampling but it still works very
  well and I couldn't really hear any difference between the two. If someone
  wants to generate real polyphase filter coefficients, they are welcome to
  submit a patch.

- The IROM now contains the 4 mixing functions used by the AX UCode: mix_add,
  mix_add_two, mix_add_ramp, mix_add_ramp_two. They are large, inlined
  functions (probably for performance reasons) in the official DSP IROM, our
  version prefers to use a loop. This *should* be more performant with our DSP
  JIT implementation, but I did not benchmark that.

Because the new DSP ROM is working just as well as the official ROM in 95% of
cases, it is now shipped by default with Dolphin and will be used with DSPLLE
if you don't have an official DSP ROM in User/GC. It will still display a panic
alert at every boot to notice you that you are using a non official DSP ROM
made by us, which is not perfect.

Games using the CARD, IPL or GBA UCodes are still broken. I don't know what
games this actually impacts, but this is a very small proportion compared to
what works.
2013-03-16 23:54:55 +01:00

1170 lines
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IROM_BASE: equ 0x8000
lri $CR, #0x00ff
lri $SR, #0x2000
si @DMBH, #0x8071
si @DMBL, #0xfeed
mainloop:
clr $ACC1
clr $ACC0
call wait_for_cpu_mbox+#IROM_BASE
;mmem-addr
param1:
lr $AC1.M, @CMBL
lri $AC0.M, #0xa001
cmp
jnz param2+#IROM_BASE
call wait_for_cpu_mbox+#IROM_BASE
lr $IX0, @CMBH
lr $IX1, @CMBL
jmp mainloop+#IROM_BASE
;iram-addr
param2:
lri $AC0.M, #0xc002
cmp
jnz param3+#IROM_BASE
call wait_for_cpu_mbox+#IROM_BASE
lr $IX2, @CMBL
jmp mainloop+#IROM_BASE
;iram-length
param3:
lri $AC0.M, #0xa002
cmp
jnz param4+#IROM_BASE
call wait_for_cpu_mbox+#IROM_BASE
lr $IX3, @CMBL
jmp mainloop+#IROM_BASE
;dram-length
param4:
lri $AC0.M, #0xb002
cmp
jnz param5+#IROM_BASE
call wait_for_cpu_mbox+#IROM_BASE
lr $AX0.L, @CMBL
jmp mainloop+#IROM_BASE
;iram-start-addr
param5:
lri $AC0.M, #0xd001
cmp
jnz mainloop+#IROM_BASE
call wait_for_cpu_mbox+#IROM_BASE
lr $AR0, @CMBL
jmp 0x80b5
wait_for_dsp_mbox:
lrs $AC0.M, @DMBH
andcf $AC0.M, #0x8000
jlz wait_for_dsp_mbox+#IROM_BASE
ret
wait_for_cpu_mbox:
lrs $AC0.M, @CMBH
andcf $AC0.M, #0x8000
jlnz wait_for_cpu_mbox+#IROM_BASE
ret
wait_dma:
lrs $AC0.M, @DSCR
andcf $AC0.M, #0x0004
jlz wait_dma+#IROM_BASE
ret
bootucode:
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sub_80b5:
set16
clr $ACC1
clr $ACC0
lris $AC0.M, #0x2
sr @DSCR, $AC0.M
sr @DSMAH, $IX0
sr @DSMAL, $IX1
sr @DSPA, $IX2
sr @DSBL, $IX3
call wait_dma+#IROM_BASE
jmpr $AR0
nop
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; 80e7
; Args:
; AR0 points to the 32 input 1 samples (s16)
; AR1 points to the volume data (init1, delta1, init2, delta2)
; AR2 points to the already mixed samples for output 1 (s32)
; AR3 points to where the output 1 should be stored (s32)
; IX0 points to the 32 input 2 samples (s16)
; IX1 points to where the output 2 should be stored (s32)
;
; Returns:
; AX0.L is the value of the last sample from input 1
; AX1.H is the value of the last sample from input 2
mix_two_add:
call mix_add+#IROM_BASE
iar $AR1
mrr $AR0, $IX0
mrr $AR2, $IX1
mrr $AR3, $IX1
mrr $IX0, $AX0.L
call mix_add+#IROM_BASE
mrr $AX1.H, $AX0.L
mrr $AX0.L, $IX0
ret
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; 81f9
; Args:
; AR0 points to the 32 input samples (s16)
; AR1 points to the volume data (init, delta)
; AR2 points to the already mixed samples (s32)
; AR3 points to where the output should be stored (s32)
;
; Returns:
; AX0.L is the value of the last sample
; AX1.H is the first address after the output
mix_add:
lrri $AX1.L, @$AR1
bloopi #32, ____mix_add_end_loop+#IROM_BASE
lrri $AC0.M, @$AR2
lrri $AC0.L, @$AR2
lsl16 $ACC0
lrri $AX0.H, @$AR0
mulx $AX0.H, $AX1.L
addp $ACC0
asr16 $ACC0
srri @$AR3, $AC0.M
____mix_add_end_loop:
srri @$AR3, $AC0.L
movp $ACC0
mrr $AX0.L, $AC0.M
mrr $AX1.H, $AR3
ret
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; 8282
mix_two_add_ramp:
call mix_add_ramp+#IROM_BASE
mrr $AR0, $IX0
mrr $AR2, $IX1
mrr $IX1, $AX0.L
call mix_add_ramp+#IROM_BASE
mrr $AX1.H, $AX0.L
mrr $AX0.L, $IX1
ret
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; 845d
mix_add_ramp:
clr $ACC0
clr $ACC1
lrri $AC0.L, @$AR1
lrrd $AC1.L, @$AR1
mrr $IX2, $AR3
bloopi #32, ____mix_add_ramp_end_ramp+#IROM_BASE
srri @$AR3, $AC0.L
____mix_add_ramp_end_ramp:
add $ACC0, $ACC1
srri @$AR1, $AC0.L
iar $AR1
mrr $IX3, $AR1
mrr $AR1, $IX2
mrr $AR3, $AR2
bloopi #32, ____mix_add_ramp_end_loop+#IROM_BASE
lrri $AC0.M, @$AR2
lrri $AC0.L, @$AR2
lsl16 $ACC0
lrri $AX0.H, @$AR0
lrri $AX1.L, @$AR1
mulx $AX0.H, $AX1.L
addp $ACC0
asr16 $ACC0
srri @$AR3, $AC0.M
____mix_add_ramp_end_loop:
srri @$AR3, $AC0.L
movp $ACC0
mrr $AX0.L, $AC0.M
mrr $AX1.H, $AR3
mrr $AR1, $IX3
mrr $AR3, $IX2
ret
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