diff options
Diffstat (limited to 'sys/arch/amd64/cpu/lapic.c')
| -rw-r--r-- | sys/arch/amd64/cpu/lapic.c | 100 |
1 files changed, 98 insertions, 2 deletions
diff --git a/sys/arch/amd64/cpu/lapic.c b/sys/arch/amd64/cpu/lapic.c index 22d07a9..def7dea 100644 --- a/sys/arch/amd64/cpu/lapic.c +++ b/sys/arch/amd64/cpu/lapic.c @@ -39,6 +39,7 @@ #include <lib/stdbool.h> #include <mu/cpu.h> #include <md/lapic.h> +#include <md/i8254.h> #include <md/cpuid.h> #include <md/msr.h> @@ -53,14 +54,28 @@ * * See section 2.3.2 of the x2APIC specification */ -#define LAPIC_REG_ID 0x0020 /* ID register */ -#define LAPIC_REG_SVR 0x00F0 /* Spurious vector register */ +#define LAPIC_REG_ID 0x0020 /* ID register */ +#define LAPIC_REG_SVR 0x00F0 /* Spurious vector register */ +#define LAPIC_REG_TICR 0x0380 /* Timer initial counter register */ +#define LAPIC_REG_TCCR 0x0390 /* Timer current counter register */ +#define LAPIC_REG_TDCR 0x03E0 /* Timer divide configuration register */ +#define LAPIC_REG_LVTTMR 0x0320 /* LVT timer entry */ /* LAPIC SVR bits */ #define LAPIC_SVR_EBS BIT(12) /* EOI-broadcast supression */ #define LAPIC_SVR_FPC BIT(9) /* Focus processor checking */ #define LAPIC_SVR_APIC_EN BIT(8) /* Software-enable Local APIC */ +/* Local vector table */ +#define LVT_MASK BIT(16) + +/* Samples to take */ +#define LAPIC_TMR_SAMPLES 0xFFFF + +/* Timer modes */ +#define LAPIC_TMR_ONESHOT 0x00 +#define LAPIC_TMR_PERIODIC 0x01 + /* Accessed via RDMSR/WRMSR */ #define X2APIC_MSR_BASE 0x00000800 @@ -126,6 +141,85 @@ lapic_has_x2apic(void) } /* + * Configure the Local APIC timer with a predefined + * vector + * + * XXX: See LAPIC_TMR_* for mode definitions + */ +static void +lapic_tmr_enable(struct mcb *mcb, uint8_t mode) +{ + uint32_t lvt_tmr; + + lvt_tmr = lapic_read(mcb, LAPIC_REG_LVTTMR); + + /* Clear out stale values */ + lvt_tmr &= ~0xFF; /* Clear vector */ + lvt_tmr &= ~(0x3 << 17); /* Clear mode */ + lvt_tmr &= ~LVT_MASK; /* Clear mask */ + + /* Set them to our own values */ + lvt_tmr |= (mode & 0x3) << 17; /* Set mode */ + lvt_tmr |= LAPIC_TMR_VEC; /* Set vector */ + lapic_write(mcb, LAPIC_REG_LVTTMR, lvt_tmr); +} + +/* + * Disable the Local APIC timer + */ +static void +lapic_tmr_disable(struct mcb *mcb) +{ + uint32_t lvt_tmr; + + lvt_tmr = lapic_read(mcb, LAPIC_REG_LVTTMR); + lvt_tmr |= LVT_MASK; /* Set mask */ + lvt_tmr &= ~0xFF; /* Clear vector; just in case */ + lapic_write(mcb, LAPIC_REG_LVTTMR, lvt_tmr); +} + +/* + * Calibrate the Local APIC timer + */ +static size_t +lapic_tmr_clbr(struct mcb *mcb) +{ + size_t freq; + uint16_t ticks_total; + uint16_t ticks_begin, ticks_end; + uint32_t tmp; + + /* + * The divide configuration register basically slices + * up the base clock (typically TSC core crystal clock or + * bus clock) which makes the counter decrement slower with + * respect to higher values + */ + tmp = lapic_read(mcb, LAPIC_REG_TDCR); + tmp &= ~BIT(3); /* Clear upper */ + tmp &= ~0x3; /* Clear lower */ + tmp |= 0x01; /* DCR=0b001[divide by 4] */ + lapic_write(mcb, LAPIC_REG_TDCR, tmp); + + lapic_tmr_disable(mcb); + i8254_set_count(LAPIC_TMR_SAMPLES); + + /* Take some samples of the counter */ + ticks_begin = i8254_get_count(); + lapic_write(mcb, LAPIC_REG_TICR, LAPIC_TMR_SAMPLES); + while (lapic_read(mcb, LAPIC_REG_TCCR) != 0); + + /* Compute the deviation [total ticks] */ + lapic_tmr_disable(mcb); + ticks_end = i8254_get_count(); + ticks_total = ticks_end - ticks_begin; + + /* Compute the frequency */ + freq = (LAPIC_TMR_SAMPLES / ticks_total) * I8254_DIVIDEND; + return freq; +} + +/* * Enable the Local APIC unit */ static void @@ -183,5 +277,7 @@ lapic_init(void) mcb = &ci->mcb; mcb->xapic_io = PHYS_TO_VIRT((uintptr_t)madt->lapic_addr); + lapic_enable(mcb); + mcb->lapic_tmr_freq = lapic_tmr_clbr(mcb); } |