Implemented optional additional serial output in the boot loader.

When the debug boot option is set, or ENABLE_SERIAL defined on compile time,
the serial port 1 is activated.
It will also read the serial base port info from the BIOS data and use
that if any ports are reported (will fall back to 0x3f8 if not).
Right now, a fixed baud rate of 115200 and 8n1 is used.


git-svn-id: file:///srv/svn/repos/haiku/trunk/current@9527 a95241bf-73f2-0310-859d-f6bbb57e9c96

src/kernel/boot/platform/bios_ia32/console.cpp

@@ -7,6 +7,7 @@
 #include <SupportDefs.h>
 #include <string.h>
 #include <util/kernel_cpp.h>
+#include <arch/cpu.h>
 #include <boot/stage2.h>
 
 #include "console.h"
@@ -20,16 +21,110 @@ class Console : public ConsoleNode {
 		virtual ssize_t WriteAt(void *cookie, off_t pos, const void *buffer, size_t bufferSize);
 };
 
+enum serial_register_offsets {
+	SERIAL_TRANSMIT_BUFFER		= 0,
+	SERIAL_RECEIVE_BUFFER		= 0,
+	SERIAL_DIVISOR_LATCH_LOW	= 0,
+	SERIAL_DIVISOR_LATCH_HIGH	= 1,
+	SERIAL_FIFO_CONTROL			= 2,
+	SERIAL_LINE_CONTROL			= 3,
+	SERIAL_MODEM_CONTROL		= 4,
+	SERIAL_LINE_STATUS			= 5,
+	SERIAL_MODEM_STATUS			= 6,
+};
+
+static const uint32 kSerialBaudRate = 115200;
+
 static uint16 *sScreenBase = (uint16 *)0xb8000;
 static uint32 sScreenWidth = 80;
 static uint32 sScreenHeight = 24;
 static uint32 sScreenOffset = 0;
 static uint16 sColor = 0x0f00;
 
+static int32 sSerialEnabled = 0;
+static uint16 sSerialBasePort = 0x3f8;
+
 static Console sInput, sOutput;
 FILE *stdin, *stdout, *stderr;
 
 
+//	serial debug output
+
+
+static void
+serial_putc(char c)
+{
+	// wait until the transmitter empty bit is set
+	while ((in8(sSerialBasePort + SERIAL_LINE_STATUS) & 0x20) == 0)
+		;
+
+	out8(c, sSerialBasePort + SERIAL_TRANSMIT_BUFFER);
+}
+
+
+static void
+serial_puts(const char *string, size_t size)
+{
+	while (size-- != 0) {
+		char c = string[0];
+
+		if (c == '\n') {
+			serial_putc('\r');
+			serial_putc('\n');
+		} else if (c != '\r')
+			serial_putc(c);
+
+		string++;
+	}
+}
+
+
+extern "C" void 
+serial_disable(void)
+{
+#if ENABLE_SERIAL
+	sSerialEnabled = 0;
+#else
+	sSerialEnabled--;
+#endif
+}
+
+
+extern "C" void 
+serial_enable(void)
+{
+	sSerialEnabled++;
+}
+
+
+static void
+serial_init(void)
+{
+	// copy the base ports of the optional 4 serial ports to the kernel args
+	// 0x0000:0x0400 is the location of that information in the BIOS data segment
+	uint16 *ports = (uint16 *)0x400;
+	memcpy(gKernelArgs.platform_args.serial_base_ports, ports, sizeof(uint16) * MAX_SERIAL_PORTS);
+
+	// only use the port if we could find one, else use the standard port
+	if (gKernelArgs.platform_args.serial_base_ports[0] != 0)
+		sSerialBasePort = gKernelArgs.platform_args.serial_base_ports[0];
+
+	uint16 divisor = uint16(115200 / kSerialBaudRate);
+
+	out8(0x80, sSerialBasePort + SERIAL_LINE_CONTROL);	/* set divisor latch access bit */
+	out8(divisor & 0xf, sSerialBasePort + SERIAL_DIVISOR_LATCH_LOW);
+	out8(divisor >> 8, sSerialBasePort + SERIAL_DIVISOR_LATCH_HIGH);
+	out8(3, sSerialBasePort + SERIAL_LINE_CONTROL);		/* 8N1 */
+
+#ifdef ENABLE_SERIAL
+	serial_enable();
+#endif
+}
+
+
+//	#pragma mark -
+
+
 static void
 scroll_up()
 {
@@ -65,6 +160,9 @@ Console::WriteAt(void *cookie, off_t /*pos*/, const void *buffer, size_t bufferS
 {
 	const char *string = (const char *)buffer;
 
+	if (sSerialEnabled > 0)
+		serial_puts(string, bufferSize);
+
 	if (gKernelArgs.frame_buffer.enabled)
 		return bufferSize;
 
@@ -133,6 +231,7 @@ console_init(void)
 {
 	// ToDo: make screen size changeable via stage2_args
 
+	serial_init();
 	console_clear_screen();
 
 	// enable stdio functionality

src/kernel/boot/platform/bios_ia32/console.h

@@ -1,6 +1,6 @@
 /*
 ** Copyright 2004, Axel Dörfler, axeld@pinc-software.de. All rights reserved.
-** Distributed under the terms of the OpenBeOS License.
+** Distributed under the terms of the Haiku License.
 */
 #ifndef CONSOLE_H
 #define CONSOLE_H
@@ -42,6 +42,9 @@ extern void console_set_color(int32 foreground, int32 background);
 
 extern status_t console_init(void);
 
+extern void serial_disable(void);
+extern void serial_enable(void);
+
 #ifdef __cplusplus
 }
 #endif

src/kernel/boot/platform/bios_ia32/start.c

@@ -123,6 +123,8 @@ _start(void)
 
 	// reading the keyboard doesn't seem to work in graphics mode (maybe a bochs problem)
 	sBootOptions = check_for_boot_keys();
+	if (sBootOptions & BOOT_OPTION_DEBUG_OUTPUT)
+		serial_enable();
 
 	main(&args);
 }