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// 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();
}
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