diff options
Diffstat (limited to 'arch/x86/boot/early_serial_console.c')
| -rw-r--r-- | arch/x86/boot/early_serial_console.c | 154 |
1 files changed, 154 insertions, 0 deletions
diff --git a/arch/x86/boot/early_serial_console.c b/arch/x86/boot/early_serial_console.c new file mode 100644 index 000000000..b25c53527 --- /dev/null +++ b/arch/x86/boot/early_serial_console.c @@ -0,0 +1,154 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Serial port routines for use during early boot reporting. This code is + * included from both the compressed kernel and the regular kernel. + */ +#include "boot.h" + +#define DEFAULT_SERIAL_PORT 0x3f8 /* ttyS0 */ + +#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 */ + +#define DEFAULT_BAUD 9600 + +static void early_serial_init(int port, int baud) +{ + unsigned char c; + unsigned divisor; + + outb(0x3, port + LCR); /* 8n1 */ + outb(0, port + IER); /* no interrupt */ + outb(0, port + FCR); /* no fifo */ + outb(0x3, port + MCR); /* DTR + RTS */ + + divisor = 115200 / baud; + c = inb(port + LCR); + outb(c | DLAB, port + LCR); + outb(divisor & 0xff, port + DLL); + outb((divisor >> 8) & 0xff, port + DLH); + outb(c & ~DLAB, port + LCR); + + early_serial_base = port; +} + +static void parse_earlyprintk(void) +{ + int baud = DEFAULT_BAUD; + char arg[32]; + int pos = 0; + int port = 0; + + if (cmdline_find_option("earlyprintk", arg, sizeof arg) > 0) { + char *e; + + if (!strncmp(arg, "serial", 6)) { + port = DEFAULT_SERIAL_PORT; + pos += 6; + } + + if (arg[pos] == ',') + pos++; + + /* + * make sure we have + * "serial,0x3f8,115200" + * "serial,ttyS0,115200" + * "ttyS0,115200" + */ + if (pos == 7 && !strncmp(arg + pos, "0x", 2)) { + port = simple_strtoull(arg + pos, &e, 16); + if (port == 0 || arg + pos == e) + port = DEFAULT_SERIAL_PORT; + else + pos = e - arg; + } else if (!strncmp(arg + pos, "ttyS", 4)) { + static const int bases[] = { 0x3f8, 0x2f8 }; + int idx = 0; + + /* += strlen("ttyS"); */ + pos += 4; + + if (arg[pos++] == '1') + idx = 1; + + port = bases[idx]; + } + + if (arg[pos] == ',') + pos++; + + baud = simple_strtoull(arg + pos, &e, 0); + if (baud == 0 || arg + pos == e) + baud = DEFAULT_BAUD; + } + + if (port) + early_serial_init(port, baud); +} + +#define BASE_BAUD (1843200/16) +static unsigned int probe_baud(int port) +{ + unsigned char lcr, dll, dlh; + unsigned int quot; + + lcr = inb(port + LCR); + outb(lcr | DLAB, port + LCR); + dll = inb(port + DLL); + dlh = inb(port + DLH); + outb(lcr, port + LCR); + quot = (dlh << 8) | dll; + + return BASE_BAUD / quot; +} + +static void parse_console_uart8250(void) +{ + char optstr[64], *options; + int baud = DEFAULT_BAUD; + int port = 0; + + /* + * console=uart8250,io,0x3f8,115200n8 + * need to make sure it is last one console ! + */ + if (cmdline_find_option("console", optstr, sizeof optstr) <= 0) + return; + + options = optstr; + + if (!strncmp(options, "uart8250,io,", 12)) + port = simple_strtoull(options + 12, &options, 0); + else if (!strncmp(options, "uart,io,", 8)) + port = simple_strtoull(options + 8, &options, 0); + else + return; + + if (options && (options[0] == ',')) + baud = simple_strtoull(options + 1, &options, 0); + else + baud = probe_baud(port); + + if (port) + early_serial_init(port, baud); +} + +void console_init(void) +{ + parse_earlyprintk(); + + if (!early_serial_base) + parse_console_uart8250(); +} |