text: #include <linux/console.h>
  #include <linux/kernel.h>
  #include <linux/init.h>
  #include <linux/string.h>
  #include <linux/screen_info.h>
  #include <linux/usb/ch9.h>
  #include <linux/pci_regs.h>
  #include <linux/pci_ids.h>
  #include <linux/errno.h>
  #include <asm/io.h>
  #include <asm/processor.h>
  #include <asm/fcntl.h>
  #include <asm/setup.h>
  #include <xen/hvc-console.h>
  #include <asm/pci-direct.h>
  #include <asm/fixmap.h>
  #include <asm/intel-mid.h>
  #include <asm/pgtable.h>
  #include <linux/usb/ehci_def.h>
  #include <linux/usb/xhci-dbgp.h>
  #include <linux/efi.h>
  #include <asm/efi.h>
  #include <asm/pci_x86.h>
  
  /* Simple VGA output */
  #define VGABASE		(__ISA_IO_base + 0xb8000)
  
  static int max_ypos = 25, max_xpos = 80;
  static int current_ypos = 25, current_xpos;
  
  static void early_vga_write(struct console *con, const char *str, unsigned n)
  {
  	char c;
  	int  i, k, j;
  
  	while ((c = *str++) != '\0' && n-- > 0) {
  		if (current_ypos >= max_ypos) {
  			/* scroll 1 line up */
  			for (k = 1, j = 0; k < max_ypos; k++, j++) {
  				for (i = 0; i < max_xpos; i++) {
  					writew(readw(VGABASE+2*(max_xpos*k+i)),
  					       VGABASE + 2*(max_xpos*j + i));
  				}
  			}
  			for (i = 0; i < max_xpos; i++)
  				writew(0x720, VGABASE + 2*(max_xpos*j + i));
  			current_ypos = max_ypos-1;
  		}
  #ifdef CONFIG_KGDB_KDB
  		if (c == '\b') {
  			if (current_xpos > 0)
  				current_xpos--;
  		} else if (c == '\r') {
  			current_xpos = 0;
  		} else
  #endif
  		if (c == '\n') {
  			current_xpos = 0;
  			current_ypos++;
  		} else if (c != '\r')  {
  			writew(((0x7 << 8) | (unsigned short) c),
  			       VGABASE + 2*(max_xpos*current_ypos +
  						current_xpos++));
  			if (current_xpos >= max_xpos) {
  				current_xpos = 0;
  				current_ypos++;
  			}
  		}
  	}
  }
  
  static struct console early_vga_console = {
  	.name =		"earlyvga",
  	.write =	early_vga_write,
  	.flags =	CON_PRINTBUFFER,
  	.index =	-1,
  };
  
  /* Serial functions loosely based on a similar package from Klaus P. Gerlicher */
  
  static unsigned long early_serial_base = 0x3f8;  /* ttyS0 */
  
  #define XMTRDY          0x20
  
  #define DLAB		0x80
  
  #define TXR             0       /*  Transmit register (WRITE) */
  #define RXR             0       /*  Receive register  (READ)  */
  #define IER             1       /*  Interrupt Enable          */
  #define IIR             2       /*  Interrupt ID              */
  #define FCR             2       /*  FIFO control              */
  #define LCR             3       /*  Line control              */
  #define MCR             4       /*  Modem control             */
  #define LSR             5       /*  Line Status               */
  #define MSR             6       /*  Modem Status              */
  #define DLL             0       /*  Divisor Latch Low         */
  #define DLH             1       /*  Divisor latch High        */
  
  static unsigned int io_serial_in(unsigned long addr, int offset)
  {
  	return inb(addr + offset);
  }
  
  static void io_serial_out(unsigned long addr, int offset, int value)
  {
  	outb(value, addr + offset);
  }
  
  static unsigned int (*serial_in)(unsigned long addr, int offset) = io_serial_in;
  static void (*serial_out)(unsigned long addr, int offset, int value) = io_serial_out;
  
  static int early_serial_putc(unsigned char ch)
  {
  	unsigned timeout = 0xffff;
  
  	while ((serial_in(early_serial_base, LSR) & XMTRDY) == 0 && --timeout)
  		cpu_relax();
  	serial_out(early_serial_base, TXR, ch);
  	return timeout ? 0 : -1;
  }
  
  static void early_serial_write(struct console *con, const char *s, unsigned n)
  {
  	while (*s && n-- > 0) {
  		if (*s == '\n')
  			early_serial_putc('\r');
  		early_serial_putc(*s);
  		s++;
  	}
  }
  
  static __init void early_serial_hw_init(unsigned divisor)
  {
  	unsigned char c;
  
  	serial_out(early_serial_base, LCR, 0x3);	/* 8n1 */
  	serial_out(early_serial_base, IER, 0);	/* no interrupt */
  	serial_out(early_serial_base, FCR, 0);	/* no fifo */
  	serial_out(early_serial_base, MCR, 0x3);	/* DTR + RTS */
  
  	c = serial_in(early_serial_base, LCR);
  	serial_out(early_serial_base, LCR, c | DLAB);
  	serial_out(early_serial_base, DLL, divisor & 0xff);
  	serial_out(early_serial_base, DLH, (divisor >> 8) & 0xff);
  	serial_out(early_serial_base, LCR, c & ~DLAB);
  }
  
  #define DEFAULT_BAUD 9600
  
  static __init void early_serial_init(char *s)
  {
  	unsigned divisor;
  	unsigned long baud = DEFAULT_BAUD;
  	char *e;
  
  	if (*s == ',')
  		++s;
  
  	if (*s) {
  		unsigned port;
  		if (!strncmp(s, "0x", 2)) {
  			early_serial_base = simple_strtoul(s, &e, 16);
  		} else {
  			static const int __initconst bases[] = { 0x3f8, 0x2f8 };
  
  			if (!strncmp(s, "ttyS", 4))
  				s += 4;
  			port = simple_strtoul(s, &e, 10);
  			if (port > 1 || s == e)
  				port = 0;
  			early_serial_base = bases[port];
  		}
  		s += strcspn(s, ",");
  		if (*s == ',')
  			s++;
  	}
  
  	if (*s) {
  		baud = simple_strtoull(s, &e, 0);
  
  		if (baud == 0 || s == e)
  			baud = DEFAULT_BAUD;
  	}
  
  	/* Convert from baud to divisor value */
  	divisor = 115200 / baud;
  
  	/* These will always be IO based ports */
  	serial_in = io_serial_in;
  	serial_out = io_serial_out;
  
  	/* Set up the HW */
  	early_serial_hw_init(divisor);
  }
  
  #ifdef CONFIG_PCI
  static void mem32_serial_out(unsigned long addr, int offset, int value)
  {
  	u32 __iomem *vaddr = (u32 __iomem *)addr;
  	/* shift implied by pointer type */
  	writel(value, vaddr + offset);
  }
  
  static unsigned int mem32_serial_in(unsigned long addr, int offset)
  {
  	u32 __iomem *vaddr = (u32 __iomem *)addr;
  	/* shift implied by pointer type */
  	return readl(vaddr + offset);
  }
  
  /*
   * early_pci_serial_init()
   *
   * This function is invoked when the early_printk param starts with "pciserial"
   * The rest of the param should be ",B:D.F,baud" where B, D & F describe the
   * location of a PCI device that must be a UART device.
   */
  static __init void early_pci_serial_init(char *s)
  {
  	unsigned divisor;
  	unsigned long baud = DEFAULT_BAUD;
  	u8 bus, slot, func;
  	u32 classcode, bar0;
  	u16 cmdreg;
  	char *e;
  
  
  	/*
  	 * First, part the param to get the BDF values
  	 */
  	if (*s == ',')
  		++s;
  
  	if (*s == 0)
  		return;
  
  	bus = (u8)simple_strtoul(s, &e, 16);
  	s = e;
  	if (*s != ':')
  		return;
  	++s;
  	slot = (u8)simple_strtoul(s, &e, 16);
  	s = e;
  	if (*s != '.')
  		return;
  	++s;
  	func = (u8)simple_strtoul(s, &e, 16);
  	s = e;
  
  	/* A baud might be following */
  	if (*s == ',')
  		s++;
  
  	/*
  	 * Second, find the device from the BDF
  	 */
  	cmdreg = read_pci_config(bus, slot, func, PCI_COMMAND);
  	classcode = read_pci_config(bus, slot, func, PCI_CLASS_REVISION);
  	bar0 = read_pci_config(bus, slot, func, PCI_BASE_ADDRESS_0);
  
  	/*
  	 * Verify it is a UART type device
  	 */
  	if (((classcode >> 16 != PCI_CLASS_COMMUNICATION_MODEM) &&
  	     (classcode >> 16 != PCI_CLASS_COMMUNICATION_SERIAL)) ||
  	   (((classcode >> 8) & 0xff) != 0x02)) /* 16550 I/F at BAR0 */
  		return;
  
  	/*
  	 * Determine if it is IO or memory mapped
  	 */
  	if (bar0 & 0x01) {
  		/* it is IO mapped */
  		serial_in = io_serial_in;
  		serial_out = io_serial_out;
  		early_serial_base = bar0&0xfffffffc;
  		write_pci_config(bus, slot, func, PCI_COMMAND,
  						cmdreg|PCI_COMMAND_IO);
  	} else {
  		/* It is memory mapped - assume 32-bit alignment */
  		serial_in = mem32_serial_in;
  		serial_out = mem32_serial_out;
  		/* WARNING! assuming the address is always in the first 4G */
  		early_serial_base =
  			(unsigned long)early_ioremap(bar0 & 0xfffffff0, 0x10);
  		write_pci_config(bus, slot, func, PCI_COMMAND,
  						cmdreg|PCI_COMMAND_MEMORY);
  	}
  
  	/*
  	 * Lastly, initialize the hardware
  	 */
  	if (*s) {
  		if (strcmp(s, "nocfg") == 0)
  			/* Sometimes, we want to leave the UART alone
  			 * and assume the BIOS has set it up correctly.
  			 * "nocfg" tells us this is the case, and we
  			 * should do no more setup.
  			 */
  			return;
  		if (kstrtoul(s, 0, &baud) < 0 || baud == 0)
  			baud = DEFAULT_BAUD;
  	}
  
  	/* Convert from baud to divisor value */
  	divisor = 115200 / baud;
  
  	/* Set up the HW */
  	early_serial_hw_init(divisor);
  }
  #endif
  
  static struct console early_serial_console = {
  	.name =		"earlyser",
  	.write =	early_serial_write,
  	.flags =	CON_PRINTBUFFER,
  	.index =	-1,
  };
  
  static void early_console_register(struct console *con, int keep_early)
  {
  	if (con->index != -1) {
  		printk(KERN_CRIT "ERROR: earlyprintk= %s already used\n",
  		       con->name);
  		return;
  	}
  	early_console = con;
  	if (keep_early)
  		early_console->flags &= ~CON_BOOT;
  	else
  		early_console->flags |= CON_BOOT;
  	register_console(early_console);
  }
  
  static int __init setup_early_printk(char *buf)
  {
  	int keep;
  
  	if (!buf)
  		return 0;
  
  	if (early_console)
  		return 0;
  
  	keep = (strstr(buf, "keep") != NULL);
  
  	while (*buf != '\0') {
  		if (!strncmp(buf, "serial", 6)) {
  			buf += 6;
  			early_serial_init(buf);
  			early_console_register(&early_serial_console, keep);
  			if (!strncmp(buf, ",ttyS", 5))
  				buf += 5;
  		}
  		if (!strncmp(buf, "ttyS", 4)) {
  			early_serial_init(buf + 4);
  			early_console_register(&early_serial_console, keep);
  		}
  #ifdef CONFIG_PCI
  		if (!strncmp(buf, "pciserial", 9)) {
  			early_pci_serial_init(buf + 9);
  			early_console_register(&early_serial_console, keep);
  			buf += 9; /* Keep from match the above "serial" */
  		}
  #endif
  		if (!strncmp(buf, "vga", 3) &&
  		    boot_params.screen_info.orig_video_isVGA == 1) {
  			max_xpos = boot_params.screen_info.orig_video_cols;
  			max_ypos = boot_params.screen_info.orig_video_lines;
  			current_ypos = boot_params.screen_info.orig_y;
  			early_console_register(&early_vga_console, keep);
  		}
  #ifdef CONFIG_EARLY_PRINTK_DBGP
  		if (!strncmp(buf, "dbgp", 4) && !early_dbgp_init(buf + 4))
  			early_console_register(&early_dbgp_console, keep);
  #endif
  #ifdef CONFIG_HVC_XEN
  		if (!strncmp(buf, "xen", 3))
  			early_console_register(&xenboot_console, keep);
  #endif
  #ifdef CONFIG_EARLY_PRINTK_EFI
  		if (!strncmp(buf, "efi", 3))
  			early_console_register(&early_efi_console, keep);
  #endif
  #ifdef CONFIG_EARLY_PRINTK_USB_XDBC
  		if (!strncmp(buf, "xdbc", 4))
  			early_xdbc_parse_parameter(buf + 4);
  #endif
  
  		buf++;
  	}
  	return 0;
  }
  
  early_param("earlyprintk", setup_early_printk);
  