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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 | // 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(); } |