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
init_port(struct earlycon_device * device)112 static void __init init_port(struct earlycon_device *device)
113 {
114 struct uart_port *port = &device->port;
115 unsigned int divisor;
116 unsigned char c;
117 unsigned int ier;
118
119 serial8250_early_out(port, UART_LCR, 0x3); /* 8n1 */
120 ier = serial8250_early_in(port, UART_IER);
121 serial8250_early_out(port, UART_IER, ier & UART_IER_UUE); /* no interrupt */
122 serial8250_early_out(port, UART_FCR, 0); /* no fifo */
123 serial8250_early_out(port, UART_MCR, 0x3); /* DTR + RTS */
124
125 if (port->uartclk) {
126 divisor = DIV_ROUND_CLOSEST(port->uartclk, 16 * device->baud);
127 c = serial8250_early_in(port, UART_LCR);
128 serial8250_early_out(port, UART_LCR, c | UART_LCR_DLAB);
129 serial8250_early_out(port, UART_DLL, divisor & 0xff);
130 serial8250_early_out(port, UART_DLM, (divisor >> 8) & 0xff);
131 serial8250_early_out(port, UART_LCR, c & ~UART_LCR_DLAB);
132 }
133 }
134
early_serial8250_setup(struct earlycon_device * device,const char * options)135 int __init early_serial8250_setup(struct earlycon_device *device,
136 const char *options)
137 {
138 if (!(device->port.membase || device->port.iobase))
139 return -ENODEV;
140
141 if (!device->baud) {
142 struct uart_port *port = &device->port;
143 unsigned int ier;
144
145 /* assume the device was initialized, only mask interrupts */
146 ier = serial8250_early_in(port, UART_IER);
147 serial8250_early_out(port, UART_IER, ier & UART_IER_UUE);
148 } else
149 init_port(device);
150
151 device->con->write = early_serial8250_write;
152 return 0;
153 }
154 EARLYCON_DECLARE(uart8250, early_serial8250_setup);
155 EARLYCON_DECLARE(uart, early_serial8250_setup);
156 OF_EARLYCON_DECLARE(ns16550, "ns16550", early_serial8250_setup);
157 OF_EARLYCON_DECLARE(ns16550a, "ns16550a", early_serial8250_setup);
158 OF_EARLYCON_DECLARE(uart, "nvidia,tegra20-uart", early_serial8250_setup);
159 OF_EARLYCON_DECLARE(uart, "snps,dw-apb-uart", early_serial8250_setup);
160
161 #ifdef CONFIG_SERIAL_8250_OMAP
162
early_omap8250_setup(struct earlycon_device * device,const char * options)163 static int __init early_omap8250_setup(struct earlycon_device *device,
164 const char *options)
165 {
166 struct uart_port *port = &device->port;
167
168 if (!(device->port.membase || device->port.iobase))
169 return -ENODEV;
170
171 port->regshift = 2;
172 device->con->write = early_serial8250_write;
173 return 0;
174 }
175
176 OF_EARLYCON_DECLARE(omap8250, "ti,omap2-uart", early_omap8250_setup);
177 OF_EARLYCON_DECLARE(omap8250, "ti,omap3-uart", early_omap8250_setup);
178 OF_EARLYCON_DECLARE(omap8250, "ti,omap4-uart", early_omap8250_setup);
179
180 #endif
181
182 #ifdef CONFIG_SERIAL_8250_RT288X
183
184 unsigned int au_serial_in(struct uart_port *p, int offset);
185 void au_serial_out(struct uart_port *p, int offset, int value);
186
early_au_setup(struct earlycon_device * dev,const char * opt)187 static int __init early_au_setup(struct earlycon_device *dev, const char *opt)
188 {
189 dev->port.serial_in = au_serial_in;
190 dev->port.serial_out = au_serial_out;
191 dev->port.iotype = UPIO_AU;
192 dev->con->write = early_serial8250_write;
193 return 0;
194 }
195 OF_EARLYCON_DECLARE(palmchip, "ralink,rt2880-uart", early_au_setup);
196
197 #endif
198
