76 lines
1.9 KiB
C
76 lines
1.9 KiB
C
#include <math.h>
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#include <kernel/x86/pit.h>
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#include <kernel/x86/io.h>
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struct pit_state pit;
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uint32_t normalize_divisor(uint32_t divisor)
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{
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if (divisor == 0)
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return 65536;
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return clamp_u32(divisor, 0, 65535);
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}
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double get_time_from_divisor(uint32_t divisor)
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{
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uint32_t _divisor = normalize_divisor(divisor);
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double clock_rate = 3579545.0 / 3.0; // This is for a bit more precision in the hz rate
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return (_divisor / (clock_rate)) * 1000;
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}
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/**
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* Im worried about an overflow
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*
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*
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* What i want to do is
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*
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* Every time we get the Timer intterupt, i want to increment a variable, just the amount of times its fired
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* and then we can use the time rate above to get total time elapsed, which we can use for sleep and stuff
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*
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* Im worried about overflows, but i can add something that will automatically flip it over? or do uints already roll over? they already rollover!!! WOOOO!!!
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* just need to be aware that only a maximum of 52ms * 32int max (64 int max) can be tracked before it rolls over!
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*/
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uint16_t read_pit_count(uint8_t channel) // Only in lobyte/hibyte mode
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{
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uint16_t count = 0;
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__asm__ volatile ("cli");
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outb(PIT_CMD_REG, (channel << 6)); // xx000000 where x is the channel
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count = inb(channel);
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count |= inb(channel) << 8;
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return count; // TODO make sure to enable interrupts after this
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}
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void set_pit_count(uint8_t channel, uint16_t count) // Only in lobyte/hibyte mode
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{
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__asm__ volatile ("cli");
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outb(channel, count & 0xFF); // low byte
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outb(channel, (count & 0xFF00) >> 8); // high byte
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// TODO: make sure to set interrupts
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}
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void init_pit(uint8_t init_command, uint8_t channel, uint32_t divisor)
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{
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uint32_t normalized_div = normalize_divisor(divisor);
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pit.divisor = normalized_div;
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pit.interrupts = 0;
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outb(PIT_CMD_REG, init_command); // access mode must be lobyte/hibyte
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outb(channel, normalized_div & 0xFF);
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outb(channel, (normalized_div & 0xFF00) >> 8);
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}
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