diff options
Diffstat (limited to 'arch/x86_64/kernel/early_printk.c')
| -rw-r--r-- | arch/x86_64/kernel/early_printk.c | 220 |
1 files changed, 220 insertions, 0 deletions
diff --git a/arch/x86_64/kernel/early_printk.c b/arch/x86_64/kernel/early_printk.c new file mode 100644 index 00000000000..750bcd0655d --- /dev/null +++ b/arch/x86_64/kernel/early_printk.c @@ -0,0 +1,220 @@ +#include <linux/console.h> +#include <linux/kernel.h> +#include <linux/init.h> +#include <linux/string.h> +#include <asm/io.h> +#include <asm/processor.h> + +/* Simple VGA output */ + +#ifdef __i386__ +#define VGABASE (__ISA_IO_base + 0xb8000) +#else +#define VGABASE ((void __iomem *)0xffffffff800b8000UL) +#endif + +#define MAX_YPOS 25 +#define MAX_XPOS 80 + +static int current_ypos = 1, current_xpos = 0; + +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; + } + 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 */ + +int 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 int early_serial_putc(unsigned char ch) +{ + unsigned timeout = 0xffff; + while ((inb(early_serial_base + LSR) & XMTRDY) == 0 && --timeout) + cpu_relax(); + outb(ch, early_serial_base + TXR); + return timeout ? 0 : -1; +} + +static void early_serial_write(struct console *con, const char *s, unsigned n) +{ + while (*s && n-- > 0) { + early_serial_putc(*s); + if (*s == '\n') + early_serial_putc('\r'); + s++; + } +} + +#define DEFAULT_BAUD 9600 + +static __init void early_serial_init(char *s) +{ + unsigned char c; + unsigned divisor; + unsigned 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 int 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++; + } + + outb(0x3, early_serial_base + LCR); /* 8n1 */ + outb(0, early_serial_base + IER); /* no interrupt */ + outb(0, early_serial_base + FCR); /* no fifo */ + outb(0x3, early_serial_base + MCR); /* DTR + RTS */ + + if (*s) { + baud = simple_strtoul(s, &e, 0); + if (baud == 0 || s == e) + baud = DEFAULT_BAUD; + } + + divisor = 115200 / baud; + c = inb(early_serial_base + LCR); + outb(c | DLAB, early_serial_base + LCR); + outb(divisor & 0xff, early_serial_base + DLL); + outb((divisor >> 8) & 0xff, early_serial_base + DLH); + outb(c & ~DLAB, early_serial_base + LCR); +} + +static struct console early_serial_console = { + .name = "earlyser", + .write = early_serial_write, + .flags = CON_PRINTBUFFER, + .index = -1, +}; + +/* Direct interface for emergencies */ +struct console *early_console = &early_vga_console; +static int early_console_initialized = 0; + +void early_printk(const char *fmt, ...) +{ + char buf[512]; + int n; + va_list ap; + + va_start(ap,fmt); + n = vscnprintf(buf,512,fmt,ap); + early_console->write(early_console,buf,n); + va_end(ap); +} + +static int keep_early; + +int __init setup_early_printk(char *opt) +{ + char *space; + char buf[256]; + + if (early_console_initialized) + return -1; + + opt = strchr(opt, '=') + 1; + + strlcpy(buf,opt,sizeof(buf)); + space = strchr(buf, ' '); + if (space) + *space = 0; + + if (strstr(buf,"keep")) + keep_early = 1; + + if (!strncmp(buf, "serial", 6)) { + early_serial_init(buf + 6); + early_console = &early_serial_console; + } else if (!strncmp(buf, "ttyS", 4)) { + early_serial_init(buf); + early_console = &early_serial_console; + } else if (!strncmp(buf, "vga", 3)) { + early_console = &early_vga_console; + } + early_console_initialized = 1; + register_console(early_console); + return 0; +} + +void __init disable_early_printk(void) +{ + if (!early_console_initialized || !early_console) + return; + if (!keep_early) { + printk("disabling early console\n"); + unregister_console(early_console); + early_console_initialized = 0; + } else { + printk("keeping early console\n"); + } +} + +__setup("earlyprintk=", setup_early_printk); |