Implement clock controller

include/stdbigos/clock.h

@@ -0,0 +1,22 @@
+#ifndef STDBIGOS_CLOCK
+#define STDBIGOS_CLOCK
+
+#include "sbi.h"
+#include "types.h"
+
+/// @ingroup stdbigos
+/// @{
+/// @ingroup clock
+/// @{
+
+u64 clock_now(void);
+u64 clock_ticks(void);
+
+struct sbiret clock_init(u64 tick_quantum);
+struct sbiret clock_rearm(void);
+struct sbiret clock_on_timer_interrupt(void);
+
+/// @}
+/// @}
+
+#endif // !STDBIGOS_CLOCK

src/example_sbi/entry.c

@@ -1,10 +1,52 @@
+#include <stdbigos/clock.h>
+#include <stdbigos/csr.h>
 #include <stdbigos/sbi.h>
+#include <stdbigos/trap.h>
 #include <stdbigos/types.h>
+#include <stdbool.h>
 
 static void sbi_puts(const char* str) {
 	while (*str) sbi_debug_console_write_byte(*str++);
 }
 
+[[gnu::interrupt("supervisor")]]
+static void int_handler() {
+	reg_t cause = CSR_READ(scause);
+	if (!is_interrupt(cause)) {
+		return;
+	}
+
+	reg_t int_no = get_interrupt_code(cause);
+	if (int_no != IntSTimer) {
+		return;
+	}
+
+	(void)clock_on_timer_interrupt();
+}
+
 void main([[maybe_unused]] u32 hartid, [[maybe_unused]] const void* fdt) {
-	sbi_puts("Hello world\n");
+	CSR_WRITE(stvec, int_handler);
+
+	struct sbiret ret = clock_init(50000llu);
+	if (ret.error != SBI_SUCCESS) {
+		sbi_puts("clock init failed\n");
+		return;
+	}
+
+	CSR_SET(sie, 1lu << IntSTimer);
+	CSR_SET(sstatus, 1lu << 1);
+
+	sbi_puts("clock started\n");
+
+	u64 last_tick = 0;
+	while (true) {
+		wfi();
+
+		u64 ticks = clock_ticks();
+		if (ticks != last_tick && (ticks % 100) == 0) {
+			sbi_puts("tick x100\n");
+		}
+
+		last_tick = ticks;
+	}
 }

src/lib/stdbigos/clock.c

@@ -0,0 +1,51 @@
+#include <stdbigos/clock.h>
+#include <stdbigos/csr.h>
+
+static u64 g_tick_quantum;
+static u64 g_next_deadline;
+static u64 g_ticks;
+
+static struct sbiret clock_program_timer(u64 deadline) {
+	struct sbiret ret = sbi_set_timer(deadline);
+	if (ret.error == SBI_ERR_NOT_SUPPORTED) {
+		return sbi_legacy_set_timer(deadline);
+	}
+
+	return ret;
+}
+
+static struct sbiret make_error(sbi_error_t error) {
+	return (struct sbiret){.error = error, .value = 0};
+}
+
+u64 clock_now(void) {
+	return CSR_READ(time);
+}
+
+u64 clock_ticks(void) {
+	return g_ticks;
+}
+
+struct sbiret clock_rearm(void) {
+	if (g_tick_quantum == 0) {
+		return make_error(SBI_ERR_INVALID_STATE);
+	}
+
+	g_next_deadline = clock_now() + g_tick_quantum;
+	return clock_program_timer(g_next_deadline);
+}
+
+struct sbiret clock_init(u64 tick_quantum) {
+	if (tick_quantum == 0) {
+		return make_error(SBI_ERR_INVALID_PARAM);
+	}
+
+	g_ticks = 0;
+	g_tick_quantum = tick_quantum;
+	return clock_rearm();
+}
+
+struct sbiret clock_on_timer_interrupt(void) {
+	++g_ticks;
+	return clock_rearm();
+}