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kernel: mask interrupts during callbacks on SH3!

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This change fixes very weird bugs first observed with the RTC, related
to IMASK not being updated when an interrupt occurs to avoid
re-interruption.

On SH4 there is a CPUOPM setting that automatically sets IMASK to the
level of the accepted interrupt, which is so exactly what every kernel
needs that I can't figure out why this isn't the only behavior.

Turns out on SH3 it's not even an option. This commit sets IMASK to 15
when accepting a callback on SH3. This most notably prevents the gray
engine from updating the screen so callbacks need to be made very short.
This commit is contained in:
Lephe 2020-07-19 20:02:50 +02:00
parent e617ea63bf
commit a06213ca11
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1 changed files with 20 additions and 5 deletions
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25
src/core/inth.S
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@ -217,13 +217,24 @@ _gint_inth_callback:
ldc r4, r0_bank
ldc r5, r4_bank
/* Enable interrupts and go back to user bank. SR.IMASK is already set
/* Enable interrupts and go back to user bank. On SH4, SR.IMASK is set
to the level of the current interrupt, which makes sure we can only
be re-interrupted by something with a higher priority. */
stc sr, r0
mov.l .SR_clear_RB_BL, r1
and r1, r0
ldc r0, sr
stc sr, r1
mov.l .SR_clear_RB_BL, r0
and r0, r1
/* On SH3, set IMASK to 15 to block interrupts while allowing TLB
misses to be handled. */
mov.l .gint, r0
mov.l @r0, r0
tst #1, r0
bt .load_sr
mov.l .SR_set_IMASK, r0
or r0, r1
.load_sr:
ldc r1, sr
/* We are now in the user bank with r0 and r4 set. Call back. We want
to forward the return value to kernel bank, but this bank can be
@ -256,3 +267,7 @@ _gint_inth_callback:
.align 4
.SR_clear_RB_BL:
.long ~((1 << 29) | (1 << 28))
.SR_set_IMASK:
.long (0xf << 4)
.gint:
.long _gint