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https://github.com/cccriscv/mini-riscv-os.git
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43 lines
1.2 KiB
C
43 lines
1.2 KiB
C
#include "timer.h"
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extern void os_kernel();
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// a scratch area per CPU for machine-mode timer interrupts.
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reg_t timer_scratch[NCPU][5];
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void timer_init()
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{
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// each CPU has a separate source of timer interrupts.
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int id = r_mhartid();
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// ask the CLINT for a timer interrupt.
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// int interval = 1000000; // cycles; about 1/10th second in qemu.
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int interval = 20000000; // cycles; about 2 second in qemu.
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*(reg_t*)CLINT_MTIMECMP(id) = *(reg_t*)CLINT_MTIME + interval;
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// prepare information in scratch[] for timervec.
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// scratch[0..2] : space for timervec to save registers.
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// scratch[3] : address of CLINT MTIMECMP register.
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// scratch[4] : desired interval (in cycles) between timer interrupts.
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reg_t *scratch = &timer_scratch[id][0];
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scratch[3] = CLINT_MTIMECMP(id);
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scratch[4] = interval;
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w_mscratch((reg_t)scratch);
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// set the machine-mode trap handler.
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w_mtvec((reg_t)sys_timer);
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// enable machine-mode interrupts.
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w_mstatus(r_mstatus() | MSTATUS_MIE);
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// enable machine-mode timer interrupts.
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w_mie(r_mie() | MIE_MTIE);
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}
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static int timer_count = 0;
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void timer_handler() {
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lib_printf("timer_handler: %d\n", ++timer_count);
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os_kernel();
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}
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