Line data Source code
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/of_device.h>
31 : #include <linux/serial_reg.h>
32 : #include <linux/serial.h>
33 : #include <linux/serial_8250.h>
34 : #include <asm/io.h>
35 : #include <asm/serial.h>
36 :
37 0 : static unsigned int serial8250_early_in(struct uart_port *port, int offset)
38 : {
39 0 : int reg_offset = offset;
40 0 : offset <<= port->regshift;
41 :
42 0 : switch (port->iotype) {
43 0 : case UPIO_MEM:
44 0 : return readb(port->membase + offset);
45 0 : case UPIO_MEM16:
46 0 : return readw(port->membase + offset);
47 0 : case UPIO_MEM32:
48 0 : return readl(port->membase + offset);
49 0 : case UPIO_MEM32BE:
50 0 : return ioread32be(port->membase + offset);
51 0 : case UPIO_PORT:
52 0 : return inb(port->iobase + offset);
53 0 : case UPIO_AU:
54 0 : return port->serial_in(port, reg_offset);
55 : default:
56 : return 0;
57 : }
58 : }
59 :
60 0 : static void serial8250_early_out(struct uart_port *port, int offset, int value)
61 : {
62 0 : int reg_offset = offset;
63 0 : offset <<= port->regshift;
64 :
65 0 : switch (port->iotype) {
66 0 : case UPIO_MEM:
67 0 : writeb(value, port->membase + offset);
68 : break;
69 0 : case UPIO_MEM16:
70 0 : writew(value, port->membase + offset);
71 : break;
72 0 : case UPIO_MEM32:
73 0 : writel(value, port->membase + offset);
74 : break;
75 0 : case UPIO_MEM32BE:
76 0 : iowrite32be(value, port->membase + offset);
77 0 : break;
78 0 : case UPIO_PORT:
79 0 : outb(value, port->iobase + offset);
80 : break;
81 0 : case UPIO_AU:
82 0 : port->serial_out(port, reg_offset, value);
83 0 : break;
84 : }
85 0 : }
86 :
87 : #define BOTH_EMPTY (UART_LSR_TEMT | UART_LSR_THRE)
88 :
89 0 : static void serial_putc(struct uart_port *port, int c)
90 : {
91 0 : unsigned int status;
92 :
93 0 : serial8250_early_out(port, UART_TX, c);
94 :
95 0 : for (;;) {
96 0 : status = serial8250_early_in(port, UART_LSR);
97 0 : if ((status & BOTH_EMPTY) == BOTH_EMPTY)
98 : break;
99 0 : cpu_relax();
100 : }
101 0 : }
102 :
103 0 : static void early_serial8250_write(struct console *console,
104 : const char *s, unsigned int count)
105 : {
106 0 : struct earlycon_device *device = console->data;
107 0 : struct uart_port *port = &device->port;
108 :
109 0 : uart_console_write(port, s, count, serial_putc);
110 0 : }
111 :
112 : #ifdef CONFIG_CONSOLE_POLL
113 : static int early_serial8250_read(struct console *console,
114 : char *s, unsigned int count)
115 : {
116 : struct earlycon_device *device = console->data;
117 : struct uart_port *port = &device->port;
118 : unsigned int status;
119 : int num_read = 0;
120 :
121 : while (num_read < count) {
122 : status = serial8250_early_in(port, UART_LSR);
123 : if (!(status & UART_LSR_DR))
124 : break;
125 : s[num_read++] = serial8250_early_in(port, UART_RX);
126 : }
127 :
128 : return num_read;
129 : }
130 : #else
131 : #define early_serial8250_read NULL
132 : #endif
133 :
134 0 : static void __init init_port(struct earlycon_device *device)
135 : {
136 0 : struct uart_port *port = &device->port;
137 0 : unsigned int divisor;
138 0 : unsigned char c;
139 0 : unsigned int ier;
140 :
141 0 : serial8250_early_out(port, UART_LCR, 0x3); /* 8n1 */
142 0 : ier = serial8250_early_in(port, UART_IER);
143 0 : serial8250_early_out(port, UART_IER, ier & UART_IER_UUE); /* no interrupt */
144 0 : serial8250_early_out(port, UART_FCR, 0); /* no fifo */
145 0 : serial8250_early_out(port, UART_MCR, 0x3); /* DTR + RTS */
146 :
147 0 : if (port->uartclk) {
148 0 : divisor = DIV_ROUND_CLOSEST(port->uartclk, 16 * device->baud);
149 0 : c = serial8250_early_in(port, UART_LCR);
150 0 : serial8250_early_out(port, UART_LCR, c | UART_LCR_DLAB);
151 0 : serial8250_early_out(port, UART_DLL, divisor & 0xff);
152 0 : serial8250_early_out(port, UART_DLM, (divisor >> 8) & 0xff);
153 0 : serial8250_early_out(port, UART_LCR, c & ~UART_LCR_DLAB);
154 : }
155 0 : }
156 :
157 0 : int __init early_serial8250_setup(struct earlycon_device *device,
158 : const char *options)
159 : {
160 0 : if (!(device->port.membase || device->port.iobase))
161 : return -ENODEV;
162 :
163 0 : if (!device->baud) {
164 0 : struct uart_port *port = &device->port;
165 0 : unsigned int ier;
166 :
167 : /* assume the device was initialized, only mask interrupts */
168 0 : ier = serial8250_early_in(port, UART_IER);
169 0 : serial8250_early_out(port, UART_IER, ier & UART_IER_UUE);
170 : } else
171 0 : init_port(device);
172 :
173 0 : device->con->write = early_serial8250_write;
174 0 : device->con->read = early_serial8250_read;
175 0 : return 0;
176 : }
177 : EARLYCON_DECLARE(uart8250, early_serial8250_setup);
178 : EARLYCON_DECLARE(uart, early_serial8250_setup);
179 : OF_EARLYCON_DECLARE(ns16550, "ns16550", early_serial8250_setup);
180 : OF_EARLYCON_DECLARE(ns16550a, "ns16550a", early_serial8250_setup);
181 : OF_EARLYCON_DECLARE(uart, "nvidia,tegra20-uart", early_serial8250_setup);
182 : OF_EARLYCON_DECLARE(uart, "snps,dw-apb-uart", early_serial8250_setup);
183 :
184 : #ifdef CONFIG_SERIAL_8250_OMAP
185 :
186 : static int __init early_omap8250_setup(struct earlycon_device *device,
187 : const char *options)
188 : {
189 : struct uart_port *port = &device->port;
190 :
191 : if (!(device->port.membase || device->port.iobase))
192 : return -ENODEV;
193 :
194 : port->regshift = 2;
195 : device->con->write = early_serial8250_write;
196 : return 0;
197 : }
198 :
199 : OF_EARLYCON_DECLARE(omap8250, "ti,omap2-uart", early_omap8250_setup);
200 : OF_EARLYCON_DECLARE(omap8250, "ti,omap3-uart", early_omap8250_setup);
201 : OF_EARLYCON_DECLARE(omap8250, "ti,omap4-uart", early_omap8250_setup);
202 :
203 : #endif
204 :
205 : #ifdef CONFIG_SERIAL_8250_RT288X
206 :
207 : static int __init early_au_setup(struct earlycon_device *dev, const char *opt)
208 : {
209 : dev->port.serial_in = au_serial_in;
210 : dev->port.serial_out = au_serial_out;
211 : dev->port.iotype = UPIO_AU;
212 : dev->con->write = early_serial8250_write;
213 : return 0;
214 : }
215 : OF_EARLYCON_DECLARE(palmchip, "ralink,rt2880-uart", early_au_setup);
216 :
217 : #endif
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