Does a lot of work towards the PIT

Added a math library, with clamp and POW.
added printf support for printing doubles
added a few helper functions in PIT for calcaulting the time in seconds of a clock cycle based on divisor
This commit is contained in:
2025-06-06 22:01:18 -04:00
parent 378f7ef23d
commit f9c2ea2f2b
10 changed files with 215 additions and 0 deletions

View File

@ -1,3 +1,64 @@
#include <math.h>
#include <kernel/x86/pit.h>
#include <kernel/x86/io.h>
struct pit_state pit;
uint32_t normalize_divisor(uint32_t divisor)
{
if (divisor == 0)
return 65536;
return clamp_u32(divisor, 0, 65535);
}
double get_time_from_divisor(uint32_t divisor)
{
uint32_t _divisor = normalize_divisor(divisor);
double clock_rate = 3579545.0 / 3.0; // This is for a bit more precision in the hz rate
return (_divisor / (clock_rate)) * 1000;
}
/**
* Im worried about an overflow
*
*
* What i want to do is
*
* Every time we get the Timer intterupt, i want to increment a variable, just the amount of times its fired
* and then we can use the time rate above to get total time elapsed, which we can use for sleep and stuff
*
* 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!!!
* just need to be aware that only a maximum of 52ms * 32int max (64 int max) can be tracked before it rolls over!
*/
uint16_t read_pit_count(uint8_t channel) // Only in lobyte/hibyte mode
{
uint16_t count = 0;
__asm__ volatile ("cli");
outb(PIT_CMD_REG, (channel << 6)); // xx000000 where x is the channel
count = inb(channel);
count |= inb(channel) << 8;
return count; // TODO make sure to enable interrupts after this
}
void set_pit_count(uint8_t channel, uint16_t count) // Only in lobyte/hibyte mode
{
__asm__ volatile ("cli");
outb(channel, count & 0xFF); // low byte
outb(channel, (count & 0xFF00) >> 8); // high byte
// TODO: make sure to set interrupts
}