1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * Early serial console for 8250/16550 devices
4 *
5 * (c) Copyright 2004 Hewlett-Packard Development Company, L.P.
6 * Bjorn Helgaas <bjorn.helgaas@hp.com>
7 *
8 * Based on the 8250.c serial driver, Copyright (C) 2001 Russell King,
9 * and on early_printk.c by Andi Kleen.
10 *
11 * This is for use before the serial driver has initialized, in
12 * particular, before the UARTs have been discovered and named.
13 * Instead of specifying the console device as, e.g., "ttyS0",
14 * we locate the device directly by its MMIO or I/O port address.
15 *
16 * The user can specify the device directly, e.g.,
17 * earlycon=uart8250,io,0x3f8,9600n8
18 * earlycon=uart8250,mmio,0xff5e0000,115200n8
19 * earlycon=uart8250,mmio32,0xff5e0000,115200n8
20 * or
21 * console=uart8250,io,0x3f8,9600n8
22 * console=uart8250,mmio,0xff5e0000,115200n8
23 * console=uart8250,mmio32,0xff5e0000,115200n8
24 */
25
26 #include <linux/tty.h>
27 #include <linux/init.h>
28 #include <linux/console.h>
29 #include <linux/of.h>
30 #include <linux/serial_reg.h>
31 #include <linux/serial.h>
32 #include <linux/serial_8250.h>
33 #include <asm/io.h>
34 #include <asm/serial.h>
35
serial8250_early_in(struct uart_port * port,int offset)36 static unsigned int serial8250_early_in(struct uart_port *port, int offset)
37 {
38 offset <<= port->regshift;
39
40 switch (port->iotype) {
41 case UPIO_MEM:
42 return readb(port->membase + offset);
43 case UPIO_MEM16:
44 return readw(port->membase + offset);
45 case UPIO_MEM32:
46 return readl(port->membase + offset);
47 case UPIO_MEM32BE:
48 return ioread32be(port->membase + offset);
49 case UPIO_PORT:
50 return inb(port->iobase + offset);
51 default:
52 return 0;
53 }
54 }
55
serial8250_early_out(struct uart_port * port,int offset,int value)56 static void serial8250_early_out(struct uart_port *port, int offset, int value)
57 {
58 offset <<= port->regshift;
59
60 switch (port->iotype) {
61 case UPIO_MEM:
62 writeb(value, port->membase + offset);
63 break;
64 case UPIO_MEM16:
65 writew(value, port->membase + offset);
66 break;
67 case UPIO_MEM32:
68 writel(value, port->membase + offset);
69 break;
70 case UPIO_MEM32BE:
71 iowrite32be(value, port->membase + offset);
72 break;
73 case UPIO_PORT:
74 outb(value, port->iobase + offset);
75 break;
76 }
77 }
78
serial_putc(struct uart_port * port,unsigned char c)79 static void serial_putc(struct uart_port *port, unsigned char c)
80 {
81 unsigned int status;
82
83 serial8250_early_out(port, UART_TX, c);
84
85 for (;;) {
86 status = serial8250_early_in(port, UART_LSR);
87 if (uart_lsr_tx_empty(status))
88 break;
89 cpu_relax();
90 }
91 }
92
early_serial8250_write(struct console * console,const char * s,unsigned int count)93 static void early_serial8250_write(struct console *console,
94 const char *s, unsigned int count)
95 {
96 struct earlycon_device *device = console->data;
97 struct uart_port *port = &device->port;
98
99 uart_console_write(port, s, count, serial_putc);
100 }
101
102 #ifdef CONFIG_CONSOLE_POLL
early_serial8250_read(struct console * console,char * s,unsigned int count)103 static int early_serial8250_read(struct console *console,
104 char *s, unsigned int count)
105 {
106 struct earlycon_device *device = console->data;
107 struct uart_port *port = &device->port;
108 unsigned int status;
109 int num_read = 0;
110
111 while (num_read < count) {
112 status = serial8250_early_in(port, UART_LSR);
113 if (!(status & UART_LSR_DR))
114 break;
115 s[num_read++] = serial8250_early_in(port, UART_RX);
116 }
117
118 return num_read;
119 }
120 #else
121 #define early_serial8250_read NULL
122 #endif
123
init_port(struct earlycon_device * device)124 static void __init init_port(struct earlycon_device *device)
125 {
126 struct uart_port *port = &device->port;
127 unsigned int divisor;
128 unsigned char c;
129 unsigned int ier;
130
131 serial8250_early_out(port, UART_LCR, UART_LCR_WLEN8); /* 8n1 */
132 ier = serial8250_early_in(port, UART_IER);
133 serial8250_early_out(port, UART_IER, ier & UART_IER_UUE); /* no interrupt */
134 serial8250_early_out(port, UART_FCR, 0); /* no fifo */
135 serial8250_early_out(port, UART_MCR, UART_MCR_DTR | UART_MCR_RTS);
136
137 if (port->uartclk) {
138 divisor = DIV_ROUND_CLOSEST(port->uartclk, 16 * device->baud);
139 c = serial8250_early_in(port, UART_LCR);
140 serial8250_early_out(port, UART_LCR, c | UART_LCR_DLAB);
141 serial8250_early_out(port, UART_DLL, divisor & 0xff);
142 serial8250_early_out(port, UART_DLM, (divisor >> 8) & 0xff);
143 serial8250_early_out(port, UART_LCR, c & ~UART_LCR_DLAB);
144 }
145 }
146
early_serial8250_setup(struct earlycon_device * device,const char * options)147 int __init early_serial8250_setup(struct earlycon_device *device,
148 const char *options)
149 {
150 if (!(device->port.membase || device->port.iobase))
151 return -ENODEV;
152
153 if (!device->baud) {
154 struct uart_port *port = &device->port;
155 unsigned int ier;
156
157 /* assume the device was initialized, only mask interrupts */
158 ier = serial8250_early_in(port, UART_IER);
159 serial8250_early_out(port, UART_IER, ier & UART_IER_UUE);
160 } else
161 init_port(device);
162
163 device->con->write = early_serial8250_write;
164 device->con->read = early_serial8250_read;
165 return 0;
166 }
167 EARLYCON_DECLARE(uart8250, early_serial8250_setup);
168 EARLYCON_DECLARE(uart, early_serial8250_setup);
169 OF_EARLYCON_DECLARE(ns16550, "ns16550", early_serial8250_setup);
170 OF_EARLYCON_DECLARE(ns16550a, "ns16550a", early_serial8250_setup);
171 OF_EARLYCON_DECLARE(uart, "nvidia,tegra20-uart", early_serial8250_setup);
172 OF_EARLYCON_DECLARE(uart, "snps,dw-apb-uart", early_serial8250_setup);
173
174 #ifdef CONFIG_SERIAL_8250_OMAP
175
early_omap8250_setup(struct earlycon_device * device,const char * options)176 static int __init early_omap8250_setup(struct earlycon_device *device,
177 const char *options)
178 {
179 struct uart_port *port = &device->port;
180
181 if (!(device->port.membase || device->port.iobase))
182 return -ENODEV;
183
184 port->regshift = 2;
185 device->con->write = early_serial8250_write;
186 return 0;
187 }
188
189 OF_EARLYCON_DECLARE(omap8250, "ti,omap2-uart", early_omap8250_setup);
190 OF_EARLYCON_DECLARE(omap8250, "ti,omap3-uart", early_omap8250_setup);
191 OF_EARLYCON_DECLARE(omap8250, "ti,omap4-uart", early_omap8250_setup);
192
193 #endif
194
