x86_64: re-enable legacy PIC and PIT initialisation

arch/x86_64/init.c

@@ -1,4 +1,7 @@
+#include "arch/serial.h"
+
 #include <arch/e820.h>
+#include <arch/pit.h>
 #include <socks/arg.h>
 #include <socks/clock.h>
 #include <socks/console.h>
@@ -49,12 +52,15 @@ void early_console_init(void)
 {
 	const char *dest = arg_value("kernel.early-console");
 	if (!dest) {
-		return;
+		dest = "ttyS0";
 	}
-}
 
-static void init_bootfb(multiboot_info_t *mb)
-{
+	if (!strcmp(dest, "tty0")) {
+		/* show log messages on VGA */
+	} else if (!strcmp(dest, "ttyS0")) {
+		/* write log messages to serial port */
+		early_serialcon_init(115200);
+	}
 }
 
 static void use_uniprocessor_topology(void)
@@ -69,19 +75,14 @@ int ml_init(uintptr_t arg)
 
 	parse_cmdline(PTR32(mb->cmdline));
 
-	init_bootfb(mb);
+	early_console_init();
 
 	bootstrap_cpu_init();
 	clock_calibrate(500);
 
-	early_console_init();
-
 	print_kernel_banner();
 
 	early_vm_init();
-	printk("video mode: %ux%u",
-	       mb->framebuffer_width,
-	       mb->framebuffer_height);
 
 	e820_scan(PTR32(mb->mmap_addr), mb->mmap_length);
 
@@ -118,6 +119,7 @@ int ml_init(uintptr_t arg)
 
 	sched_init();
 
+	pit_start(500);
 	ml_int_enable();
 
 	return 0;