driver/rtc: RTC ticker at 1024Hz

driver/irq/pic/rtc/handler.S

@@ -0,0 +1,29 @@
+format elf64
+
+public __pic_rtc_IRQ8
+public __pic_rtc_IRQHandler;
+
+
+section '.bss' writable
+__pic_rtc_IRQHandler:
+	rq 1
+
+section '.text' executable
+__pic_rtc_IRQ8:
+	push rax
+
+	; read the register C byte or the interrupt will block
+	mov al, 0x0c
+	out 0x70, al
+	in  al, 0x71   
+
+	; tell if the irq handler is NULL
+	mov  rax, [__pic_rtc_IRQHandler]
+	test rax, rax
+	pop  rax
+	jz  .end
+	jmp qword [__pic_rtc_IRQHandler]
+.end:
+	iret
+
+

driver/irq/pic/rtc/internal.h

@@ -0,0 +1,8 @@
+#pragma once
+
+#include "rtc.h"
+#include "../../../../main.h"
+
+
+extern void * __pic_rtc_IRQHandler;
+SYSV_ABI void __pic_rtc_IRQ8();

driver/irq/pic/rtc/rtc.c

@@ -0,0 +1,34 @@
+
+#include "rtc.h"
+#include "internal.h"
+#include "../pic.h"
+#include "../internal.h"
+#include "../../../../main.h"
+#include "../../../../runtime/panic_assert.h"
+#include "../../../../interrupt/interrupt.h"
+
+
+bool pic_rtc_Enabled;
+
+void pic_rtc_Init() {
+	assert(irq_pic_Enabled && "pic/rtc requires pic to be enabled");
+
+	if (pic_rtc_Enabled)
+		return;
+	INTERRUPT_DISABLE;
+
+	outb(0x70, 0x8b);         // select register B, and disable NMI
+	uint8_t prev = inb(0x71); // read the current value of register B
+	outb(0x70, 0x8B);         // set the index again (a read will reset the index to register D)
+	outb(0x71, prev | 0x40);  // write the previous value ORed with 0x40. This turns on bit 6 of register B
+
+	irq_pic_IRQHandlerRaw[8] = __pic_rtc_IRQ8;
+	irq_pic_Mask(8, false);
+
+	pic_rtc_Enabled = true;
+	INTERRUPT_RESTORE;
+}
+
+void pic_rtc_SetHandler(void *handler) {
+	__pic_rtc_IRQHandler = handler;
+}

driver/irq/pic/rtc/rtc.h

@@ -0,0 +1,24 @@
+#pragma once
+
+#include <stdint.h>
+#include <stdbool.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+
+extern bool pic_rtc_Enabled;
+
+// Init installs the required interrupt handlers.
+void pic_rtc_Init();
+
+// SetHandler sets the interrupt handler for RTC interrupts.
+//
+// The handler is jumped to, so it must use IRET and save registers is uses.
+void pic_rtc_SetHandler(void *handler);
+
+
+#ifdef __cplusplus
+}
+#endif