1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * Serial port routines for use during early boot reporting. This code is 4 * included from both the compressed kernel and the regular kernel. 5 */ 6 #include "boot.h" 7 8 #define DEFAULT_SERIAL_PORT 0x3f8 /* ttyS0 */ 9 10 #define DLAB 0x80 11 12 #define TXR 0 /* Transmit register (WRITE) */ 13 #define RXR 0 /* Receive register (READ) */ 14 #define IER 1 /* Interrupt Enable */ 15 #define IIR 2 /* Interrupt ID */ 16 #define FCR 2 /* FIFO control */ 17 #define LCR 3 /* Line control */ 18 #define MCR 4 /* Modem control */ 19 #define LSR 5 /* Line Status */ 20 #define MSR 6 /* Modem Status */ 21 #define DLL 0 /* Divisor Latch Low */ 22 #define DLH 1 /* Divisor latch High */ 23 24 #define DEFAULT_BAUD 9600 25 26 static void early_serial_init(int port, int baud) 27 { 28 unsigned char c; 29 unsigned divisor; 30 31 outb(0x3, port + LCR); /* 8n1 */ 32 outb(0, port + IER); /* no interrupt */ 33 outb(0, port + FCR); /* no fifo */ 34 outb(0x3, port + MCR); /* DTR + RTS */ 35 36 divisor = 115200 / baud; 37 c = inb(port + LCR); 38 outb(c | DLAB, port + LCR); 39 outb(divisor & 0xff, port + DLL); 40 outb((divisor >> 8) & 0xff, port + DLH); 41 outb(c & ~DLAB, port + LCR); 42 43 early_serial_base = port; 44 } 45 46 static void parse_earlyprintk(void) 47 { 48 int baud = DEFAULT_BAUD; 49 char arg[32]; 50 int pos = 0; 51 int port = 0; 52 53 if (cmdline_find_option("earlyprintk", arg, sizeof(arg)) > 0) { 54 char *e; 55 56 if (!strncmp(arg, "serial", 6)) { 57 port = DEFAULT_SERIAL_PORT; 58 pos += 6; 59 } 60 61 if (arg[pos] == ',') 62 pos++; 63 64 /* 65 * make sure we have 66 * "serial,0x3f8,115200" 67 * "serial,ttyS0,115200" 68 * "ttyS0,115200" 69 */ 70 if (pos == 7 && !strncmp(arg + pos, "0x", 2)) { 71 port = simple_strtoull(arg + pos, &e, 16); 72 if (port == 0 || arg + pos == e) 73 port = DEFAULT_SERIAL_PORT; 74 else 75 pos = e - arg; 76 } else if (!strncmp(arg + pos, "ttyS", 4)) { 77 static const int bases[] = { 0x3f8, 0x2f8 }; 78 int idx = 0; 79 80 /* += strlen("ttyS"); */ 81 pos += 4; 82 83 if (arg[pos++] == '1') 84 idx = 1; 85 86 port = bases[idx]; 87 } 88 89 if (arg[pos] == ',') 90 pos++; 91 92 baud = simple_strtoull(arg + pos, &e, 0); 93 if (baud == 0 || arg + pos == e) 94 baud = DEFAULT_BAUD; 95 } 96 97 if (port) 98 early_serial_init(port, baud); 99 } 100 101 #define BASE_BAUD (1843200/16) 102 static unsigned int probe_baud(int port) 103 { 104 unsigned char lcr, dll, dlh; 105 unsigned int quot; 106 107 lcr = inb(port + LCR); 108 outb(lcr | DLAB, port + LCR); 109 dll = inb(port + DLL); 110 dlh = inb(port + DLH); 111 outb(lcr, port + LCR); 112 quot = (dlh << 8) | dll; 113 114 return BASE_BAUD / quot; 115 } 116 117 static void parse_console_uart8250(void) 118 { 119 char optstr[64], *options; 120 int baud = DEFAULT_BAUD; 121 int port = 0; 122 123 /* 124 * console=uart8250,io,0x3f8,115200n8 125 * need to make sure it is last one console ! 126 */ 127 if (cmdline_find_option("console", optstr, sizeof(optstr)) <= 0) 128 return; 129 130 options = optstr; 131 132 if (!strncmp(options, "uart8250,io,", 12)) 133 port = simple_strtoull(options + 12, &options, 0); 134 else if (!strncmp(options, "uart,io,", 8)) 135 port = simple_strtoull(options + 8, &options, 0); 136 else 137 return; 138 139 if (options && (options[0] == ',')) 140 baud = simple_strtoull(options + 1, &options, 0); 141 else 142 baud = probe_baud(port); 143 144 if (port) 145 early_serial_init(port, baud); 146 } 147 148 void console_init(void) 149 { 150 parse_earlyprintk(); 151 152 if (!early_serial_base) 153 parse_console_uart8250(); 154 } 155