155 lines
3.5 KiB
C
155 lines
3.5 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* Serial port routines for use during early boot reporting. This code is
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* included from both the compressed kernel and the regular kernel.
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*/
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#include "boot.h"
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#define DEFAULT_SERIAL_PORT 0x3f8 /* ttyS0 */
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#define DLAB 0x80
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#define TXR 0 /* Transmit register (WRITE) */
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#define RXR 0 /* Receive register (READ) */
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#define IER 1 /* Interrupt Enable */
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#define IIR 2 /* Interrupt ID */
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#define FCR 2 /* FIFO control */
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#define LCR 3 /* Line control */
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#define MCR 4 /* Modem control */
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#define LSR 5 /* Line Status */
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#define MSR 6 /* Modem Status */
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#define DLL 0 /* Divisor Latch Low */
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#define DLH 1 /* Divisor latch High */
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#define DEFAULT_BAUD 9600
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static void early_serial_init(int port, int baud)
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{
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unsigned char c;
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unsigned divisor;
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outb(0x3, port + LCR); /* 8n1 */
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outb(0, port + IER); /* no interrupt */
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outb(0, port + FCR); /* no fifo */
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outb(0x3, port + MCR); /* DTR + RTS */
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divisor = 115200 / baud;
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c = inb(port + LCR);
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outb(c | DLAB, port + LCR);
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outb(divisor & 0xff, port + DLL);
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outb((divisor >> 8) & 0xff, port + DLH);
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outb(c & ~DLAB, port + LCR);
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early_serial_base = port;
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}
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static void parse_earlyprintk(void)
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{
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int baud = DEFAULT_BAUD;
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char arg[32];
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int pos = 0;
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int port = 0;
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if (cmdline_find_option("earlyprintk", arg, sizeof arg) > 0) {
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char *e;
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if (!strncmp(arg, "serial", 6)) {
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port = DEFAULT_SERIAL_PORT;
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pos += 6;
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}
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if (arg[pos] == ',')
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pos++;
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/*
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* make sure we have
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* "serial,0x3f8,115200"
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* "serial,ttyS0,115200"
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* "ttyS0,115200"
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*/
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if (pos == 7 && !strncmp(arg + pos, "0x", 2)) {
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port = simple_strtoull(arg + pos, &e, 16);
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if (port == 0 || arg + pos == e)
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port = DEFAULT_SERIAL_PORT;
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else
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pos = e - arg;
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} else if (!strncmp(arg + pos, "ttyS", 4)) {
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static const int bases[] = { 0x3f8, 0x2f8 };
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int idx = 0;
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/* += strlen("ttyS"); */
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pos += 4;
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if (arg[pos++] == '1')
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idx = 1;
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port = bases[idx];
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}
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if (arg[pos] == ',')
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pos++;
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baud = simple_strtoull(arg + pos, &e, 0);
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if (baud == 0 || arg + pos == e)
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baud = DEFAULT_BAUD;
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}
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if (port)
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early_serial_init(port, baud);
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}
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#define BASE_BAUD (1843200/16)
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static unsigned int probe_baud(int port)
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{
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unsigned char lcr, dll, dlh;
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unsigned int quot;
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lcr = inb(port + LCR);
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outb(lcr | DLAB, port + LCR);
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dll = inb(port + DLL);
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dlh = inb(port + DLH);
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outb(lcr, port + LCR);
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quot = (dlh << 8) | dll;
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return BASE_BAUD / quot;
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}
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static void parse_console_uart8250(void)
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{
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char optstr[64], *options;
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int baud = DEFAULT_BAUD;
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int port = 0;
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/*
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* console=uart8250,io,0x3f8,115200n8
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* need to make sure it is last one console !
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*/
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if (cmdline_find_option("console", optstr, sizeof optstr) <= 0)
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return;
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options = optstr;
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if (!strncmp(options, "uart8250,io,", 12))
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port = simple_strtoull(options + 12, &options, 0);
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else if (!strncmp(options, "uart,io,", 8))
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port = simple_strtoull(options + 8, &options, 0);
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else
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return;
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if (options && (options[0] == ','))
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baud = simple_strtoull(options + 1, &options, 0);
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else
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baud = probe_baud(port);
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if (port)
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early_serial_init(port, baud);
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}
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void console_init(void)
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{
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parse_earlyprintk();
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if (!early_serial_base)
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parse_console_uart8250();
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}
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