diff options
| -rw-r--r-- | dev/timer/x86_generic/x86_pit.c | 91 |
1 files changed, 25 insertions, 66 deletions
diff --git a/dev/timer/x86_generic/x86_pit.c b/dev/timer/x86_generic/x86_pit.c index 9f4ba9c3..6c74e37a 100644 --- a/dev/timer/x86_generic/x86_pit.c +++ b/dev/timer/x86_generic/x86_pit.c @@ -29,38 +29,29 @@ #include <dev/timer/x86_pit.h> #include <err.h> #include <lib/fixed_point.h> +#include <lk/trace.h> #include <platform/interrupts.h> #include <platform/timer.h> +#define LOCAL_TRACE 0 + static platform_timer_callback t_callback; static struct fp_32_64 ms_per_tsc; static struct fp_32_64 ns_per_tsc; -static struct fp_32_64 ticks_per_ms; +static struct fp_32_64 pit_ticks_per_ns; /* The oscillator used by the PIT chip runs at 1.193182MHz */ #define INTERNAL_FREQ 1193182UL -/* Maximum amount of time that can be program, in milliseconds */ -#define MAX_TIMER_INTERVAL 55 - -/* - * Freqency in HZ of the timer. - * TODO: Select the frequency in platform_set_oneshot_timer based on the time - * we actually need to sleep so we don't wake up more often than needed when - * sleeping more than 55ms and so we get better precision when sleeping - * significantly less than 55ms. - */ -#define PIT_FREQUENCY 1000 - /* Mode/Command register */ #define I8253_CONTROL_REG 0x43 /* Channel 0 data port */ #define I8253_DATA_REG 0x40 -static uint64_t lk_time_to_ticks(lk_time_t lk_time) +static uint64_t lk_time_ns_to_pit_ticks(lk_time_ns_t lk_time_ns) { - return u64_mul_u32_fp32_64(lk_time, ticks_per_ms); + return u64_mul_u64_fp32_64(lk_time_ns, pit_ticks_per_ns); } static lk_time_t tsc_cnt_to_lk_time(uint64_t tsc_cnt) @@ -127,7 +118,7 @@ lk_time_t current_time(void) return tsc_cnt_to_lk_time(__rdtsc()); } -static enum handler_return os_timer_tick(void* arg) +static enum handler_return x86_pit_timer_interrupt_handler(void* arg) { if (t_callback) { return t_callback(arg, current_time_ns()); @@ -136,43 +127,13 @@ static enum handler_return os_timer_tick(void* arg) } } -static void set_pit_frequency(uint32_t frequency) -{ - struct fp_32_64 result; - uint16_t count; - - /* Figure out the correct divisor for the desired frequency */ - if (frequency < 1) { - dprintf(SPEW, "invalid frequency, %u, use max count\n", frequency); - count = 0xffff; - } else if (frequency >= INTERNAL_FREQ) { - dprintf(SPEW, "invalid frequency, %u, use min count\n", frequency); - count = 1; - } else { - fp_32_64_div_32_32(&result, INTERNAL_FREQ, frequency); - if (result.l0 > 0xffff) { - dprintf(SPEW, "invalid frequency, %u, use max count\n", frequency); - count = 0xffff; - } else { - count = result.l0 & 0xffff; - } - } - - /* - * Setup the Programmable Interval Timer - * Counter 0, mode 2, binary counter, LSB followed by MSB - */ - outp(I8253_CONTROL_REG, 0x34); - outp(I8253_DATA_REG, count & 0xff); - outp(I8253_DATA_REG, count >> 8); -} - static void x86_pit_init_conversion_factors(void) { uint64_t begin, end; uint8_t status = 0; + uint16_t ticks_per_ms = INTERNAL_FREQ / 1000; - fp_32_64_div_32_32(&ticks_per_ms, INTERNAL_FREQ, 1000); + fp_32_64_div_32_32(&pit_ticks_per_ns, INTERNAL_FREQ, 1000000000); /* Set PIT mode to count down and set OUT pin high when count reaches 0 */ outp(I8253_CONTROL_REG, 0x30); @@ -191,9 +152,9 @@ static void x86_pit_init_conversion_factors(void) serializing_instruction(); /* Write LSB in counter 0 */ - outp(I8253_DATA_REG, ticks_per_ms.l0 & 0xff); + outp(I8253_DATA_REG, ticks_per_ms & 0xff); /* Write MSB in counter 0 */ - outp(I8253_DATA_REG, ticks_per_ms.l0 >> 8); + outp(I8253_DATA_REG, ticks_per_ms >> 8); do { /* Read-back command, count MSB, counter 0 */ @@ -222,33 +183,30 @@ void x86_init_pit(void) x86_pit_init_conversion_factors(); - /* 1ms granularity */ - set_pit_frequency(PIT_FREQUENCY); - - register_int_handler(INT_PIT, &os_timer_tick, NULL); + register_int_handler(INT_PIT, &x86_pit_timer_interrupt_handler, NULL); unmask_interrupt(INT_PIT); } status_t platform_set_oneshot_timer(platform_timer_callback callback, - lk_time_ns_t time_ns) + lk_time_ns_t time_ns_abs) { - uint32_t count; + uint64_t pit_ticks; + uint32_t pit_ticks_clamped; uint16_t divisor; - uint32_t time_ms; + lk_time_ns_t time_ns_rel = time_ns_abs - current_time_ns(); t_callback = callback; - /* Set millisecond timer with interval */ - time_ms = (time_ns - current_time_ns()) / (1000UL * 1000); - if (time_ms > MAX_TIMER_INTERVAL) { - time_ms = MAX_TIMER_INTERVAL; - } else if (time_ms < 1) { - time_ms = 1; - } + pit_ticks = lk_time_ns_to_pit_ticks(time_ns_rel); + /* Clamp ticks to 1 - 0x10000. 0 in the 16 bit counter means 0x10000 */ + pit_ticks_clamped = MAX(1, MIN(pit_ticks, UINT16_MAX + 1)); + divisor = pit_ticks_clamped & UINT16_MAX; - count = lk_time_to_ticks(time_ms); + LTRACEF("time_ns_abs %" PRIu64 " -> time_ns_rel %" PRIu64 + " -> pit_ticks %" PRIu64 " -> pit_ticks_clamped %" PRIu32 + " -> pit_ticks %" PRIu16 "\n", + time_ns_abs, time_ns_rel, pit_ticks, pit_ticks_clamped, divisor); - divisor = count & 0xffff; /* * Program PIT in the software strobe configuration, to send one pulse * after the count reach 0 @@ -262,6 +220,7 @@ status_t platform_set_oneshot_timer(platform_timer_callback callback, void platform_stop_timer(void) { + LTRACE; /* Enable interrupt mode that will stop the decreasing counter of the PIT */ outp(I8253_CONTROL_REG, 0x30); } |