x86_64: write printk messages to COM1 serial port

arch/x86_64/include/arch/serial.h

@@ -18,6 +18,8 @@ extern char serial_recv_byte(int device);
 
 extern int serial_rcvd(int device);
 
+extern void serialcon_init(void);
+
 #ifdef __cplusplus
 }
 #endif

arch/x86_64/init.c

@@ -12,6 +12,7 @@
 #include <socks/machine/cpu.h>
 #include <socks/libc/stdio.h>
 #include <arch/vgacon.h>
+#include <arch/serial.h>
 #include <arch/acpi.h>
 
 #define PTR32(x) ((void *)((uintptr_t)(x)))
@@ -47,6 +48,7 @@ int ml_init(uintptr_t arg)
 
 	bootstrap_cpu_init();
 	vgacon_init();
+	serialcon_init();
 	clock_calibrate(500);
 
 	print_kernel_banner();

arch/x86_64/serial.c

@@ -1,14 +1,27 @@
+#include <socks/console.h>
+#include <socks/printk.h>
+#include <socks/panic.h>
 #include <arch/serial.h>
 #include <arch/ports.h>
 
+#define COM1 0x3F8
+#define COM2 0x2F8
+#define COM3 0x3E8
+#define COM4 0x2E8
+
 static int transmit_empty(int device)
 {
 	return inportb(device + 5) & 0x20;
 }
 
+static int serial_received(int device)
+{
+	return inportb(device + 5) & 0x1;
+}
+
 void serial_send_byte(int device, char out)
 {
-    unsigned int _count = 0;
+	volatile unsigned int _count = 0;
 	while (!transmit_empty(device)) {
 		_count++;
 	}
@@ -28,3 +41,52 @@ void serial_putchar(int port, char ch)
 
 	serial_send_byte(port, ch);
 }
+
+void serialcon_write(struct console *con, const char *s, unsigned int len)
+{
+	for (unsigned int i = 0; i < len; i++) {
+		serial_putchar(COM1, s[i]);
+	}
+}
+
+static void init_serial_port(int port)
+{
+	outportb(port + 1, 0x00);    // Disable all interrupts
+	outportb(port + 3, 0x80);    // Enable DLAB (set baud rate divisor)
+	outportb(port + 0, 0x03);    // Set divisor to 3 (lo byte) 38400 baud
+	outportb(port + 1, 0x00);    //                  (hi byte)
+	outportb(port + 3, 0x03);    // 8 bits, no parity, one stop bit
+	outportb(port + 2, 0xC7);    // Enable FIFO, clear them, with 14-byte threshold
+	outportb(port + 4, 0x0B);    // IRQs enabled, RTS/DSR set
+	outportb(port + 4, 0x1E);    // Set in loopback mode, test the serial chip
+	outportb(port + 0, 0xAE);    // Test serial chip (send byte 0xAE and check if serial returns same byte)
+
+	volatile unsigned int q = 0;
+	while (!serial_received(port)) {
+		q++;
+	}
+
+	// Check if serial is faulty (i.e: not same byte as sent)
+	if(inportb(port + 0) != 0xAE) {
+		panic("serial: port %x init failed", port);
+		return;
+	}
+
+	// If serial is not faulty set it in normal operation mode
+	// (not-loopback with IRQs enabled and OUT#1 and OUT#2 bits enabled)
+	outportb(port + 4, 0x0F);
+	printk("serial: port %x initialised", port);
+}
+
+static struct console serialcon = {
+	.c_name = "serialcon",
+	.c_flags = CON_BOOT,
+	.c_write = serialcon_write,
+	.c_lock = SPIN_LOCK_INIT,
+};
+
+void serialcon_init(void)
+{
+	init_serial_port(COM1);
+	console_register(&serialcon);
+}

arch/x86_64/vgacon.c

@@ -76,7 +76,7 @@ static void handle_ctrl(int c)
 
 static void vgacon_putchar(int c)
 {
-	serial_putchar(SERIAL_PORT_A, c);
+	//serial_putchar(SERIAL_PORT_A, c);
 
 	if (iscntrl(c)) {
 		handle_ctrl(c);