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root / lab2 / timer.c @ 23

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#include <lcom/lcf.h>
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#include <lcom/timer.h>
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#include <stdint.h>
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#include "i8254.h"
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int no_interrupts = 0;
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int (timer_set_frequency)(uint8_t timer, uint32_t freq) {
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    // Frequencies out this range are not supported (by limitation of hardware)
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    if (freq > TIMER_FREQ || freq < TIMER_MIN_FREQ) return 1;
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    uint8_t status = 0;
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    if (timer_get_conf(timer, &status)) return 1;
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    //Make command
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    uint8_t write_cmd = 0;
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    //Select timer
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    switch(timer) {
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        case 0: write_cmd |= TIMER_SEL0; break;
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        case 1: write_cmd |= TIMER_SEL1; break;
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        case 2: write_cmd |= TIMER_SEL2; break;
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        default: return 1;               break;
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    }
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    //Change both LSB and MSB
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    write_cmd |= TIMER_LSB_MSB;
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    //Keep 4 least significant bits
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    write_cmd |= (status & (TIMER_MODE_MASK | TIMER_BCD));
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    //Write cmd
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    if (sys_outb(TIMER_CTRL, write_cmd)) return 1;
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    // counter_init = clock/freq
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    uint16_t counter_init = (uint16_t)(TIMER_FREQ / freq);
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    int timer_port = 0;
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    switch(timer) {
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        case 0: timer_port = TIMER_0; break;
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        case 1: timer_port = TIMER_1; break;
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        case 2: timer_port = TIMER_2; break;
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        default: return 1;            break;
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    }
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    uint8_t lsb = 0, msb = 0;
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    if (util_get_LSB(counter_init, &lsb)) return 1;
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    if (util_get_MSB(counter_init, &msb)) return 1;
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    if (sys_outb(timer_port, lsb)) return 1;
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    if (sys_outb(timer_port, msb)) return 1;
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    return 0;
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}
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int hook_id = 2;
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int (timer_subscribe_int)(uint8_t *bit_no) {
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    if(sys_irqsetpolicy(TIMER0_IRQ, IRQ_REENABLE, &hook_id)) return 1;
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    *bit_no = hook_id;
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    return 0;
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}
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int (timer_unsubscribe_int)() {
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    if(sys_irqrmpolicy(&hook_id)) return 1;
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    return 0;
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}
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void (timer_int_handler)() {
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    no_interrupts++;
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}
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int (timer_get_conf)(uint8_t timer, uint8_t *st) {
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    // Write read-back command to TIMER_CTRL
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    u32_t cmd = TIMER_RB_CMD | TIMER_RB_COUNT_ | TIMER_RB_SEL(timer);
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    if(sys_outb(TIMER_CTRL, cmd)) return 1;
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    int read_port;
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    switch(timer) {
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        case 0: read_port = TIMER_0; break;
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        case 1: read_port = TIMER_1; break;
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        case 2: read_port = TIMER_2; break;
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        default: return 1;           break;
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    }
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    if(util_sys_inb(read_port, st)) return 1;
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    return 0;
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}
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int (timer_display_conf)(uint8_t timer, uint8_t st, enum timer_status_field field) {
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    union timer_status_field_val conf;
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    uint8_t in_mode;
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    switch(field){
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        case tsf_all:
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            conf.byte = st;
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            break;
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        case tsf_initial:
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            in_mode = (st & TIMER_INMODE_MASK) >> TIMER_INMODE_POS;
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            switch(in_mode){
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                case 0: conf.in_mode = INVAL_val    ; break; //000
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                case 1: conf.in_mode = LSB_only     ; break; //001
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                case 2: conf.in_mode = MSB_only     ; break; //010
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                case 3: conf.in_mode = MSB_after_LSB; break; //011
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                default: return 1; break;
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            }
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            break;
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        case tsf_mode:
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            conf.count_mode = (st & TIMER_MODE_MASK)>>TIMER_MODE_POS;
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            if(conf.count_mode == TIMER_MODE_2ALT || conf.count_mode == TIMER_MODE_3ALT)
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                conf.count_mode &= TIMER_MODE_RED2;
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            break;
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        case tsf_base:
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            conf.bcd = st & TIMER_BCD;
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            break;
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        default: return 1; break;
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    }
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    if(timer_print_config(timer, field, conf)) return 1;
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    return 0;
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}