GNU Linux-libre 4.9.309-gnu1
[releases.git] / drivers / tty / serial / 8250 / 8250_early.c
1 /*
2  * Early serial console for 8250/16550 devices
3  *
4  * (c) Copyright 2004 Hewlett-Packard Development Company, L.P.
5  *      Bjorn Helgaas <bjorn.helgaas@hp.com>
6  *
7  * This program is free software; you can redistribute it and/or modify
8  * it under the terms of the GNU General Public License version 2 as
9  * published by the Free Software Foundation.
10  *
11  * Based on the 8250.c serial driver, Copyright (C) 2001 Russell King,
12  * and on early_printk.c by Andi Kleen.
13  *
14  * This is for use before the serial driver has initialized, in
15  * particular, before the UARTs have been discovered and named.
16  * Instead of specifying the console device as, e.g., "ttyS0",
17  * we locate the device directly by its MMIO or I/O port address.
18  *
19  * The user can specify the device directly, e.g.,
20  *      earlycon=uart8250,io,0x3f8,9600n8
21  *      earlycon=uart8250,mmio,0xff5e0000,115200n8
22  *      earlycon=uart8250,mmio32,0xff5e0000,115200n8
23  * or
24  *      console=uart8250,io,0x3f8,9600n8
25  *      console=uart8250,mmio,0xff5e0000,115200n8
26  *      console=uart8250,mmio32,0xff5e0000,115200n8
27  */
28
29 #include <linux/tty.h>
30 #include <linux/init.h>
31 #include <linux/console.h>
32 #include <linux/of.h>
33 #include <linux/of_device.h>
34 #include <linux/serial_reg.h>
35 #include <linux/serial.h>
36 #include <linux/serial_8250.h>
37 #include <asm/io.h>
38 #include <asm/serial.h>
39
40 static unsigned int __init serial8250_early_in(struct uart_port *port, int offset)
41 {
42         offset <<= port->regshift;
43
44         switch (port->iotype) {
45         case UPIO_MEM:
46                 return readb(port->membase + offset);
47         case UPIO_MEM16:
48                 return readw(port->membase + offset);
49         case UPIO_MEM32:
50                 return readl(port->membase + offset);
51         case UPIO_MEM32BE:
52                 return ioread32be(port->membase + offset);
53         case UPIO_PORT:
54                 return inb(port->iobase + offset);
55         default:
56                 return 0;
57         }
58 }
59
60 static void __init serial8250_early_out(struct uart_port *port, int offset, int value)
61 {
62         offset <<= port->regshift;
63
64         switch (port->iotype) {
65         case UPIO_MEM:
66                 writeb(value, port->membase + offset);
67                 break;
68         case UPIO_MEM16:
69                 writew(value, port->membase + offset);
70                 break;
71         case UPIO_MEM32:
72                 writel(value, port->membase + offset);
73                 break;
74         case UPIO_MEM32BE:
75                 iowrite32be(value, port->membase + offset);
76                 break;
77         case UPIO_PORT:
78                 outb(value, port->iobase + offset);
79                 break;
80         }
81 }
82
83 #define BOTH_EMPTY (UART_LSR_TEMT | UART_LSR_THRE)
84
85 static void __init serial_putc(struct uart_port *port, int c)
86 {
87         unsigned int status;
88
89         serial8250_early_out(port, UART_TX, c);
90
91         for (;;) {
92                 status = serial8250_early_in(port, UART_LSR);
93                 if ((status & BOTH_EMPTY) == BOTH_EMPTY)
94                         break;
95                 cpu_relax();
96         }
97 }
98
99 static void __init early_serial8250_write(struct console *console,
100                                         const char *s, unsigned int count)
101 {
102         struct earlycon_device *device = console->data;
103         struct uart_port *port = &device->port;
104
105         uart_console_write(port, s, count, serial_putc);
106 }
107
108 static void __init init_port(struct earlycon_device *device)
109 {
110         struct uart_port *port = &device->port;
111         unsigned int divisor;
112         unsigned char c;
113         unsigned int ier;
114
115         serial8250_early_out(port, UART_LCR, 0x3);      /* 8n1 */
116         ier = serial8250_early_in(port, UART_IER);
117         serial8250_early_out(port, UART_IER, ier & UART_IER_UUE); /* no interrupt */
118         serial8250_early_out(port, UART_FCR, 0);        /* no fifo */
119         serial8250_early_out(port, UART_MCR, 0x3);      /* DTR + RTS */
120
121         divisor = DIV_ROUND_CLOSEST(port->uartclk, 16 * device->baud);
122         c = serial8250_early_in(port, UART_LCR);
123         serial8250_early_out(port, UART_LCR, c | UART_LCR_DLAB);
124         serial8250_early_out(port, UART_DLL, divisor & 0xff);
125         serial8250_early_out(port, UART_DLM, (divisor >> 8) & 0xff);
126         serial8250_early_out(port, UART_LCR, c & ~UART_LCR_DLAB);
127 }
128
129 int __init early_serial8250_setup(struct earlycon_device *device,
130                                          const char *options)
131 {
132         if (!(device->port.membase || device->port.iobase))
133                 return -ENODEV;
134
135         if (!device->baud) {
136                 struct uart_port *port = &device->port;
137                 unsigned int ier;
138
139                 /* assume the device was initialized, only mask interrupts */
140                 ier = serial8250_early_in(port, UART_IER);
141                 serial8250_early_out(port, UART_IER, ier & UART_IER_UUE);
142         } else
143                 init_port(device);
144
145         device->con->write = early_serial8250_write;
146         return 0;
147 }
148 EARLYCON_DECLARE(uart8250, early_serial8250_setup);
149 EARLYCON_DECLARE(uart, early_serial8250_setup);
150 OF_EARLYCON_DECLARE(ns16550, "ns16550", early_serial8250_setup);
151 OF_EARLYCON_DECLARE(ns16550a, "ns16550a", early_serial8250_setup);
152 OF_EARLYCON_DECLARE(uart, "nvidia,tegra20-uart", early_serial8250_setup);
153 OF_EARLYCON_DECLARE(uart, "snps,dw-apb-uart", early_serial8250_setup);
154
155 #ifdef CONFIG_SERIAL_8250_OMAP
156
157 static int __init early_omap8250_setup(struct earlycon_device *device,
158                                        const char *options)
159 {
160         struct uart_port *port = &device->port;
161
162         if (!(device->port.membase || device->port.iobase))
163                 return -ENODEV;
164
165         port->regshift = 2;
166         device->con->write = early_serial8250_write;
167         return 0;
168 }
169
170 OF_EARLYCON_DECLARE(omap8250, "ti,omap2-uart", early_omap8250_setup);
171 OF_EARLYCON_DECLARE(omap8250, "ti,omap3-uart", early_omap8250_setup);
172 OF_EARLYCON_DECLARE(omap8250, "ti,omap4-uart", early_omap8250_setup);
173
174 #endif