initial hpet support

for now only a few wait functions are supported

src/arch/x86_64/hpet.c

@@ -0,0 +1,108 @@
+#include <arch/hpet.h>
+#include <arch/acpi.h>
+#include <arch/pci.h>
+#include <arch/panic.h>
+#include <kernel/vmm.h>
+#include <arch/mmu.h>
+#include <stdio.h>
+
+#define REGISTER_CAPABILITIES 0
+#define REGISTER_CONFIGURATION 0x10
+#define REGISTER_INTERRUPT 0x20
+#define REGISTER_COUNTER 0xF0
+#define REGISTER_N_CONFIG 0x100
+#define REGISTER_N_COMPARATOR 0x108
+#define REGISTER_N_FSB 0x110
+
+static uint16_t mintick;
+static void* volatile hpetaddr;
+static uint32_t period;
+static uint64_t nsperiod;
+static uint8_t  compcount;
+static uint64_t ticksper100ns;
+
+static inline void writetocompn(size_t n, size_t offset, uint64_t data){
+	*(uint64_t* volatile)(hpetaddr + 0x20*n + offset) = data;
+}
+
+static inline uint64_t readfromcompn(size_t n, size_t offset){
+	return *(uint64_t* volatile)(hpetaddr + 0x100 + 0x20*n + offset);
+}
+
+static inline uint64_t readfromreg(size_t offset){
+	return *(uint64_t* volatile)(hpetaddr + offset);
+}
+
+static inline void writetoreg(size_t offset, uint64_t data){
+	*(uint64_t* volatile)(hpetaddr + offset) = data;
+}
+
+static void wait_ticks(size_t ticks){
+
+	size_t end = readfromreg(REGISTER_COUNTER) + ticks;
+	
+	while(readfromreg(REGISTER_COUNTER) < end) asm("pause");
+}
+
+void hpet_wait_us(size_t us){
+
+	size_t usticks = ticksper100ns*10;
+	
+	wait_ticks(usticks*us);
+	
+}
+
+void hpet_wait_ms(size_t ms){
+	size_t msticks = ticksper100ns*10000;
+	
+	wait_ticks(ms*msticks);
+
+}
+
+void hpet_wait_s(size_t s){
+	size_t sticks = ticksper100ns*10000000;
+
+	wait_ticks(s*sticks);
+
+}
+
+void hpet_init(){
+	
+	hpet_t* hpet = acpi_gettable("HPET", 0);
+
+	if(!hpet)
+		_panic("No HPET found!\n", 0);
+
+	printf("HPET table at %p\n", hpet);
+
+	mintick = hpet->mintick;
+	
+	if(hpet->spacetype == 1) _panic("I/O space hpet not supported", 0);
+
+	printf("HPET configuration space is at %p\n", hpet->address);
+	
+	// seabios doesn't report this in the memory map.....
+	
+	hpetaddr = vmm_alloc(1, 0);
+	vmm_map((void*)hpet->address, hpetaddr, 1, ARCH_MMU_MAP_READ | ARCH_MMU_MAP_WRITE);
+	
+	uint64_t capabilities = readfromreg(REGISTER_CAPABILITIES);
+	
+	compcount = (capabilities >> 8) & 0b11111;
+	period = (capabilities >> 32) & 0xFFFFFFFF;
+	nsperiod = period / 1000000;
+	ticksper100ns = 100000000 / period;
+
+	printf("%lu comparators at %lu femtosecond ticks (%lu ns, %lu ticks per 100 ns)\n", compcount, period, nsperiod, ticksper100ns);
+	
+	// configure so we don't use legacy replacement and clear the counter
+	
+	writetoreg(REGISTER_CONFIGURATION, 0); // stop it
+	writetoreg(REGISTER_COUNTER, 0);
+	writetoreg(REGISTER_CONFIGURATION, 1); // turn it back on
+
+	// TODO add interrupt support. for now only direct reads to the 
+	// counter will be supported.
+	// (this should be enough for calibrating the CPU specific timers)
+	
+}