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
37static 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
60static 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
89static 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
103static 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
113static 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
134static 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
157int __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}
177EARLYCON_DECLARE(uart8250, early_serial8250_setup);
178EARLYCON_DECLARE(uart, early_serial8250_setup);
179OF_EARLYCON_DECLARE(ns16550, "ns16550", early_serial8250_setup);
180OF_EARLYCON_DECLARE(ns16550a, "ns16550a", early_serial8250_setup);
181OF_EARLYCON_DECLARE(uart, "nvidia,tegra20-uart", early_serial8250_setup);
182OF_EARLYCON_DECLARE(uart, "snps,dw-apb-uart", early_serial8250_setup);
183
184#ifdef CONFIG_SERIAL_8250_OMAP
185
186static 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
199OF_EARLYCON_DECLARE(omap8250, "ti,omap2-uart", early_omap8250_setup);
200OF_EARLYCON_DECLARE(omap8250, "ti,omap3-uart", early_omap8250_setup);
201OF_EARLYCON_DECLARE(omap8250, "ti,omap4-uart", early_omap8250_setup);
202OF_EARLYCON_DECLARE(omap8250, "ti,am654-uart", early_omap8250_setup);
203
204#endif
205
206#ifdef CONFIG_SERIAL_8250_RT288X
207
208unsigned int au_serial_in(struct uart_port *p, int offset);
209void au_serial_out(struct uart_port *p, int offset, int value);
210
211static int __init early_au_setup(struct earlycon_device *dev, const char *opt)
212{
213	dev->port.serial_in = au_serial_in;
214	dev->port.serial_out = au_serial_out;
215	dev->port.iotype = UPIO_AU;
216	dev->con->write = early_serial8250_write;
217	return 0;
218}
219OF_EARLYCON_DECLARE(palmchip, "ralink,rt2880-uart", early_au_setup);
220
221#endif
222