1 // SPDX-License-Identifier: GPL-2.0
3  * Serial port routines for use during early boot reporting. This code is
26 static void early_serial_init(int port, int baud)  in early_serial_init()  argument
31 	outb(0x3, port + LCR);	/* 8n1 */  in early_serial_init()
32 	outb(0, port + IER);	/* no interrupt */  in early_serial_init()
33 	outb(0, port + FCR);	/* no fifo */  in early_serial_init()
34 	outb(0x3, port + MCR);	/* DTR + RTS */  in early_serial_init()
37 	c = inb(port + LCR);  in early_serial_init()
38 	outb(c | DLAB, port + LCR);  in early_serial_init()
39 	outb(divisor & 0xff, port + DLL);  in early_serial_init()
40 	outb((divisor >> 8) & 0xff, port + DLH);  in early_serial_init()
41 	outb(c & ~DLAB, port + LCR);  in early_serial_init()
43 	early_serial_base = port;  in early_serial_init()
51 	int port = 0;  in parse_earlyprintk()  local
57 			port = DEFAULT_SERIAL_PORT;  in parse_earlyprintk()
71 			port = simple_strtoull(arg + pos, &e, 16);  in parse_earlyprintk()
72 			if (port == 0 || arg + pos == e)  in parse_earlyprintk()
73 				port = DEFAULT_SERIAL_PORT;  in parse_earlyprintk()
75 				pos = e - arg;  in parse_earlyprintk()
86 			port = bases[idx];  in parse_earlyprintk()
97 	if (port)  in parse_earlyprintk()
98 		early_serial_init(port, baud);  in parse_earlyprintk()
102 static unsigned int probe_baud(int port)  in probe_baud()  argument
107 	lcr = inb(port + LCR);  in probe_baud()
108 	outb(lcr | DLAB, port + LCR);  in probe_baud()
109 	dll = inb(port + DLL);  in probe_baud()
110 	dlh = inb(port + DLH);  in probe_baud()
111 	outb(lcr, port + LCR);  in probe_baud()
112 	quot = (dlh << 8) | dll;  in probe_baud()
121 	int port = 0;  in parse_console_uart8250()  local
133 		port = simple_strtoull(options + 12, &options, 0);  in parse_console_uart8250()
134 	else if (!strncmp(options, "uart,io,", 8))  in parse_console_uart8250()
135 		port = simple_strtoull(options + 8, &options, 0);  in parse_console_uart8250()
142 		baud = probe_baud(port);  in parse_console_uart8250()
144 	if (port)  in parse_console_uart8250()
145 		early_serial_init(port, baud);  in parse_console_uart8250()