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AS3525v1/2: Enable nested handling of interrupts

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Mostly for the sake of reducing latency for audio servicing where other service
routines can take a long time to complete, leading to occasional drops of a
few samples, especially in recording, where they are fairly frequent.

One mystery that remains is GPIOA IRQ being interrupted causes strange
undefined instruction exceptions, most easily produced on my Fuze V2 with a
scrollwheel. Making GPIOA the top ISR for now, thus not interruptible, cures it.

SVC mode is used during the actual calls. Hopefully the SVC stack size is
sufficient. Prologue and epilogue code only uses the IRQ stack and is large
enough.

Any routine code that should not be interrupted should disable IRQ itself from
here on in.


git-svn-id: svn://svn.rockbox.org/rockbox/trunk@31642 a1c6a512-1295-4272-9138-f99709370657
This commit is contained in:
Michael Sevakis 2012-01-08 22:29:25 +00:00
parent 5e21bbf575
commit 307cb04948
8 changed files with 105 additions and 48 deletions
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29
firmware/target/arm/crt0.S
View file

@ -100,17 +100,23 @@ newstart:
strhi r4, [r2], #4
bhi 1b
/* Set up stack for IRQ mode */
/* Set up stack for IRQ mode */
msr cpsr_c, #0xd2
ldr sp, =irq_stack
/* Set up stack for FIQ mode */
msr cpsr_c, #0xd3
#if CONFIG_CPU == AS3525 || CONFIG_CPU == AS3525v2
/* Let abort and undefined modes use irq stack */
/* svc stack is for interrupt processing */
ldr sp, =svc_stack
#else
/* Let svc, abort and undefined modes use irq stack */
ldr sp, =irq_stack
/* Set up stack for FIQ mode */
msr cpsr_c, #0xd1
ldr sp, =fiq_stack
/* Let svc, abort and undefined modes use irq stack */
msr cpsr_c, #0xd3
ldr sp, =irq_stack
#endif
msr cpsr_c, #0xd7
ldr sp, =irq_stack
msr cpsr_c, #0xdb
@ -159,15 +165,20 @@ prefetch_abort_handler:
b UIE
data_abort_handler:
sub r0, lr, #8
sub r0, lr, #8
mov r1, #2
b UIE
/* Cache-align interrupt stacks */
.balign 32
/* 256 words of IRQ stack */
.space 256*4
irq_stack:
/* 256 words of FIQ stack */
/* 256 words of FIQ/SVC stack */
.space 256*4
fiq_stack:
end:
svc_stack:
end: