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154 lines
3.5 KiB
154 lines
3.5 KiB
// 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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