kernel: initial hpet support

kernel-src/arch/x86-64/hpet.c

@@ -0,0 +1,55 @@
+#include <arch/acpi.h>
+#include <time.h>
+#include <logging.h>
+#include <arch/hpet.h>
+#include <kernel/vmm.h>
+
+#define HPET_REG_CAPS 0
+#define HPET_REG_CONFIG 2
+#define HPET_REG_INTSTATUS 4
+#define HPET_REG_COUNTER 0x1e
+
+#define CAP_FSPERTICK(x) (((x) >> 32) & 0xffffffff)
+
+// XXX there might be several hpets in a system.
+static volatile uint64_t *hpet;
+static time_t ticksperus;
+
+static uint64_t read64(int reg) {
+	return hpet[reg];
+}
+
+static void write64(int reg, uint64_t v) {
+	hpet[reg] = v;
+}
+
+void arch_hpet_waitticks(time_t ticks) {
+	uint64_t target = read64(HPET_REG_COUNTER) + ticks;
+	while (target > read64(HPET_REG_COUNTER)) asm volatile("pause");
+}
+
+void arch_hpet_waitus(time_t us) {
+	arch_hpet_waitticks(us * ticksperus);
+}
+
+bool arch_hpet_exists() {
+	return arch_acpi_findtable("HPET", 0) != NULL;
+}
+
+void arch_hpet_init() {
+	__assert(arch_hpet_exists());
+	hpet_t *table = arch_acpi_findtable("HPET", 0);
+	printf("hpet%lu: %lu bits %lu comparators\n", table->hpetnum, 32 + table->countersize * 32, table->comparatorcount);
+	__assert(table->countersize); // XXX not rely on hpet being 64 bits
+	__assert(table->addrid == 0);
+	__assert((table->addr & PAGE_SIZE) == 0);
+	hpet = vmm_map(NULL, PAGE_SIZE, VMM_FLAGS_PHYSICAL, ARCH_MMU_FLAGS_READ | ARCH_MMU_FLAGS_WRITE | ARCH_MMU_FLAGS_NOEXEC, (void *)table->addr);
+	__assert(hpet);
+	ticksperus = 1000000000 / CAP_FSPERTICK(read64(HPET_REG_CAPS));
+	printf("hpet%lu: %lu ticks per us (%lu fs per tick)\n", table->hpetnum, ticksperus, CAP_FSPERTICK(read64(HPET_REG_CAPS)));
+	__assert(ticksperus);
+
+	write64(HPET_REG_CONFIG, 0);
+	write64(HPET_REG_COUNTER, 0);
+	write64(HPET_REG_CONFIG, 1);
+}

kernel-src/arch/x86-64/main.c

@@ -11,6 +11,7 @@
 #include <kernel/alloc.h>
 #include <arch/acpi.h>
 #include <arch/apic.h>
+#include <arch/hpet.h>
 
 static cpu_t bsp_cpu;
 
@@ -29,5 +30,6 @@ void kernel_entry() {
 	arch_acpi_init();
 	arch_apic_init();
 	arch_apic_initap();
+	arch_hpet_init();
 	__assert(!"kernel entry end");
 }