2 * Early serial console for 8250/16550 devices
4 * (c) Copyright 2004 Hewlett-Packard Development Company, L.P.
5 * Bjorn Helgaas <bjorn.helgaas@hp.com>
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.
11 * Based on the 8250.c serial driver, Copyright (C) 2001 Russell King,
12 * and on early_printk.c by Andi Kleen.
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.
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
24 * console=uart8250,io,0x3f8,9600n8
25 * console=uart8250,mmio,0xff5e0000,115200n8
26 * console=uart8250,mmio32,0xff5e0000,115200n8
29 #include <linux/tty.h>
30 #include <linux/init.h>
31 #include <linux/console.h>
33 #include <linux/of_device.h>
34 #include <linux/serial_reg.h>
35 #include <linux/serial.h>
36 #include <linux/serial_8250.h>
38 #include <asm/serial.h>
40 static unsigned int __init serial8250_early_in(struct uart_port *port, int offset)
42 int reg_offset = offset;
43 offset <<= port->regshift;
45 switch (port->iotype) {
47 return readb(port->membase + offset);
49 return readw(port->membase + offset);
51 return readl(port->membase + offset);
53 return ioread32be(port->membase + offset);
55 return inb(port->iobase + offset);
57 return port->serial_in(port, reg_offset);
63 static void __init serial8250_early_out(struct uart_port *port, int offset, int value)
65 int reg_offset = offset;
66 offset <<= port->regshift;
68 switch (port->iotype) {
70 writeb(value, port->membase + offset);
73 writew(value, port->membase + offset);
76 writel(value, port->membase + offset);
79 iowrite32be(value, port->membase + offset);
82 outb(value, port->iobase + offset);
85 port->serial_out(port, reg_offset, value);
90 #define BOTH_EMPTY (UART_LSR_TEMT | UART_LSR_THRE)
92 static void __init serial_putc(struct uart_port *port, int c)
96 serial8250_early_out(port, UART_TX, c);
99 status = serial8250_early_in(port, UART_LSR);
100 if ((status & BOTH_EMPTY) == BOTH_EMPTY)
106 static void __init early_serial8250_write(struct console *console,
107 const char *s, unsigned int count)
109 struct earlycon_device *device = console->data;
110 struct uart_port *port = &device->port;
112 uart_console_write(port, s, count, serial_putc);
115 static void __init init_port(struct earlycon_device *device)
117 struct uart_port *port = &device->port;
118 unsigned int divisor;
122 serial8250_early_out(port, UART_LCR, 0x3); /* 8n1 */
123 ier = serial8250_early_in(port, UART_IER);
124 serial8250_early_out(port, UART_IER, ier & UART_IER_UUE); /* no interrupt */
125 serial8250_early_out(port, UART_FCR, 0); /* no fifo */
126 serial8250_early_out(port, UART_MCR, 0x3); /* DTR + RTS */
128 divisor = DIV_ROUND_CLOSEST(port->uartclk, 16 * device->baud);
129 c = serial8250_early_in(port, UART_LCR);
130 serial8250_early_out(port, UART_LCR, c | UART_LCR_DLAB);
131 serial8250_early_out(port, UART_DLL, divisor & 0xff);
132 serial8250_early_out(port, UART_DLM, (divisor >> 8) & 0xff);
133 serial8250_early_out(port, UART_LCR, c & ~UART_LCR_DLAB);
136 int __init early_serial8250_setup(struct earlycon_device *device,
139 if (!(device->port.membase || device->port.iobase))
143 struct uart_port *port = &device->port;
146 /* assume the device was initialized, only mask interrupts */
147 ier = serial8250_early_in(port, UART_IER);
148 serial8250_early_out(port, UART_IER, ier & UART_IER_UUE);
152 device->con->write = early_serial8250_write;
155 EARLYCON_DECLARE(uart8250, early_serial8250_setup);
156 EARLYCON_DECLARE(uart, early_serial8250_setup);
157 OF_EARLYCON_DECLARE(ns16550, "ns16550", early_serial8250_setup);
158 OF_EARLYCON_DECLARE(ns16550a, "ns16550a", early_serial8250_setup);
159 OF_EARLYCON_DECLARE(uart, "nvidia,tegra20-uart", early_serial8250_setup);
160 OF_EARLYCON_DECLARE(uart, "snps,dw-apb-uart", early_serial8250_setup);
162 #ifdef CONFIG_SERIAL_8250_OMAP
164 static int __init early_omap8250_setup(struct earlycon_device *device,
167 struct uart_port *port = &device->port;
169 if (!(device->port.membase || device->port.iobase))
173 device->con->write = early_serial8250_write;
177 OF_EARLYCON_DECLARE(omap8250, "ti,omap2-uart", early_omap8250_setup);
178 OF_EARLYCON_DECLARE(omap8250, "ti,omap3-uart", early_omap8250_setup);
179 OF_EARLYCON_DECLARE(omap8250, "ti,omap4-uart", early_omap8250_setup);
183 #ifdef CONFIG_SERIAL_8250_RT288X
185 unsigned int au_serial_in(struct uart_port *p, int offset);
186 void au_serial_out(struct uart_port *p, int offset, int value);
188 static int __init early_au_setup(struct earlycon_device *dev, const char *opt)
190 dev->port.serial_in = au_serial_in;
191 dev->port.serial_out = au_serial_out;
192 dev->port.iotype = UPIO_AU;
193 dev->con->write = early_serial8250_write;
196 OF_EARLYCON_DECLARE(palmchip, "ralink,rt2880-uart", early_au_setup);