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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 r4, r0_bank
ldc r5, r4_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 to the level of the current interrupt, which makes sure we can only
be re-interrupted by something with a higher priority. */ be re-interrupted by something with a higher priority. */
stc sr, r0 stc sr, r1
mov.l .SR_clear_RB_BL, r1 mov.l .SR_clear_RB_BL, r0
and r1, r0 and r0, r1
ldc r0, sr
/* 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 /* 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 to forward the return value to kernel bank, but this bank can be
@ -256,3 +267,7 @@ _gint_inth_callback:
.align 4 .align 4
.SR_clear_RB_BL: .SR_clear_RB_BL:
.long ~((1 << 29) | (1 << 28)) .long ~((1 << 29) | (1 << 28))
.SR_set_IMASK:
.long (0xf << 4)
.gint:
.long _gint