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more explicable scratch area size for machine-mode timer interrupts

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This commit is contained in:
Robert Morris 2020-10-05 15:28:01 -04:00
parent 0c55849d28
commit 6c16759503
2 changed files with 12 additions and 12 deletions
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8
kernel/kernelvec.S
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@ -93,8 +93,8 @@ kernelvec:
timervec:
# start.c has set up the memory that mscratch points to:
# scratch[0,8,16] : register save area.
# scratch[32] : address of CLINT's MTIMECMP register.
# scratch[40] : desired interval between interrupts.
# scratch[24] : address of CLINT's MTIMECMP register.
# scratch[32] : desired interval between interrupts.
csrrw a0, mscratch, a0
sd a1, 0(a0)
@ -103,8 +103,8 @@ timervec:
# schedule the next timer interrupt
# by adding interval to mtimecmp.
ld a1, 32(a0) # CLINT_MTIMECMP(hart)
ld a2, 40(a0) # interval
ld a1, 24(a0) # CLINT_MTIMECMP(hart)
ld a2, 32(a0) # interval
ld a3, 0(a1)
add a3, a3, a2
sd a3, 0(a1)

16
kernel/start.c
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@ -10,8 +10,8 @@ void timerinit();
// entry.S needs one stack per CPU.
__attribute__ ((aligned (16))) char stack0[4096 * NCPU];
// scratch area for timer interrupt, one per CPU.
uint64 mscratch0[NCPU * 32];
// a scratch area per CPU for machine-mode timer interrupts.
uint64 timer_scratch[NCPU][5];
// assembly code in kernelvec.S for machine-mode timer interrupt.
extern void timervec();
@ -64,12 +64,12 @@ timerinit()
*(uint64*)CLINT_MTIMECMP(id) = *(uint64*)CLINT_MTIME + interval;
// prepare information in scratch[] for timervec.
// scratch[0..3] : space for timervec to save registers.
// scratch[4] : address of CLINT MTIMECMP register.
// scratch[5] : desired interval (in cycles) between timer interrupts.
uint64 *scratch = &mscratch0[32 * id];
scratch[4] = CLINT_MTIMECMP(id);
scratch[5] = interval;
// scratch[0..2] : space for timervec to save registers.
// scratch[3] : address of CLINT MTIMECMP register.
// scratch[4] : desired interval (in cycles) between timer interrupts.
uint64 *scratch = &timer_scratch[id][0];
scratch[3] = CLINT_MTIMECMP(id);
scratch[4] = interval;
w_mscratch((uint64)scratch);
// set the machine-mode trap handler.