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
serial8250_early_in(struct uart_port * port,int offset)37 static unsigned int serial8250_early_in(struct uart_port *port, int offset)
38 {
39 int reg_offset = offset;
40 offset <<= port->regshift;
41
42 switch (port->iotype) {
43 case UPIO_MEM:
44 return readb(port->membase + offset);
45 case UPIO_MEM16:
46 return readw(port->membase + offset);
47 case UPIO_MEM32:
48 return readl(port->membase + offset);
49 case UPIO_MEM32BE:
50 return ioread32be(port->membase + offset);
51 case UPIO_PORT:
52 return inb(port->iobase + offset);
53 case UPIO_AU:
54 return port->serial_in(port, reg_offset);
55 default:
56 return 0;
57 }
58 }
59
serial8250_early_out(struct uart_port * port,int offset,int value)60 static void serial8250_early_out(struct uart_port *port, int offset, int value)
61 {
62 int reg_offset = offset;
63 offset <<= port->regshift;
64
65 switch (port->iotype) {
66 case UPIO_MEM:
67 writeb(value, port->membase + offset);
68 break;
69 case UPIO_MEM16:
70 writew(value, port->membase + offset);
71 break;
72 case UPIO_MEM32:
73 writel(value, port->membase + offset);
74 break;
75 case UPIO_MEM32BE:
76 iowrite32be(value, port->membase + offset);
77 break;
78 case UPIO_PORT:
79 outb(value, port->iobase + offset);
80 break;
81 case UPIO_AU:
82 port->serial_out(port, reg_offset, value);
83 break;
84 }
85 }
86
87 #define BOTH_EMPTY (UART_LSR_TEMT | UART_LSR_THRE)
88
serial_putc(struct uart_port * port,int c)89 static void serial_putc(struct uart_port *port, int c)
90 {
91 unsigned int status;
92
93 serial8250_early_out(port, UART_TX, c);
94
95 for (;;) {
96 status = serial8250_early_in(port, UART_LSR);
97 if ((status & BOTH_EMPTY) == BOTH_EMPTY)
98 break;
99 cpu_relax();
100 }
101 }
102
early_serial8250_write(struct console * console,const char * s,unsigned int count)103 static void early_serial8250_write(struct console *console,
104 const char *s, unsigned int count)
105 {
106 struct earlycon_device *device = console->data;
107 struct uart_port *port = &device->port;
108
109 uart_console_write(port, s, count, serial_putc);
110 }
111
112 #ifdef CONFIG_CONSOLE_POLL
early_serial8250_read(struct console * console,char * s,unsigned int count)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
init_port(struct earlycon_device * device)134 static void __init init_port(struct earlycon_device *device)
135 {
136 struct uart_port *port = &device->port;
137 unsigned int divisor;
138 unsigned char c;
139 unsigned int ier;
140
141 serial8250_early_out(port, UART_LCR, 0x3); /* 8n1 */
142 ier = serial8250_early_in(port, UART_IER);
143 serial8250_early_out(port, UART_IER, ier & UART_IER_UUE); /* no interrupt */
144 serial8250_early_out(port, UART_FCR, 0); /* no fifo */
145 serial8250_early_out(port, UART_MCR, 0x3); /* DTR + RTS */
146
147 if (port->uartclk) {
148 divisor = DIV_ROUND_CLOSEST(port->uartclk, 16 * device->baud);
149 c = serial8250_early_in(port, UART_LCR);
150 serial8250_early_out(port, UART_LCR, c | UART_LCR_DLAB);
151 serial8250_early_out(port, UART_DLL, divisor & 0xff);
152 serial8250_early_out(port, UART_DLM, (divisor >> 8) & 0xff);
153 serial8250_early_out(port, UART_LCR, c & ~UART_LCR_DLAB);
154 }
155 }
156
early_serial8250_setup(struct earlycon_device * device,const char * options)157 int __init early_serial8250_setup(struct earlycon_device *device,
158 const char *options)
159 {
160 if (!(device->port.membase || device->port.iobase))
161 return -ENODEV;
162
163 if (!device->baud) {
164 struct uart_port *port = &device->port;
165 unsigned int ier;
166
167 /* assume the device was initialized, only mask interrupts */
168 ier = serial8250_early_in(port, UART_IER);
169 serial8250_early_out(port, UART_IER, ier & UART_IER_UUE);
170 } else
171 init_port(device);
172
173 device->con->write = early_serial8250_write;
174 device->con->read = early_serial8250_read;
175 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
early_omap8250_setup(struct earlycon_device * device,const char * options)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 unsigned int au_serial_in(struct uart_port *p, int offset);
208 void au_serial_out(struct uart_port *p, int offset, int value);
209
early_au_setup(struct earlycon_device * dev,const char * opt)210 static int __init early_au_setup(struct earlycon_device *dev, const char *opt)
211 {
212 dev->port.serial_in = au_serial_in;
213 dev->port.serial_out = au_serial_out;
214 dev->port.iotype = UPIO_AU;
215 dev->con->write = early_serial8250_write;
216 return 0;
217 }
218 OF_EARLYCON_DECLARE(palmchip, "ralink,rt2880-uart", early_au_setup);
219
220 #endif
221
