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/serial_reg.h>
31#include <linux/serial.h>
32#include <linux/serial_8250.h>
33#include <asm/io.h>
34#include <asm/serial.h>
35
36static unsigned int serial8250_early_in(struct uart_port *port, int offset)
37{
38 offset <<= port->regshift;
39
40 switch (port->iotype) {
41 case UPIO_MEM:
42 return readb(addr: port->membase + offset);
43 case UPIO_MEM16:
44 return readw(addr: port->membase + offset);
45 case UPIO_MEM32:
46 return readl(addr: port->membase + offset);
47 case UPIO_MEM32BE:
48 return ioread32be(port->membase + offset);
49#ifdef CONFIG_HAS_IOPORT
50 case UPIO_PORT:
51 return inb(port: port->iobase + offset);
52#endif
53 default:
54 return 0;
55 }
56}
57
58static void serial8250_early_out(struct uart_port *port, int offset, int value)
59{
60 offset <<= port->regshift;
61
62 switch (port->iotype) {
63 case UPIO_MEM:
64 writeb(val: value, addr: port->membase + offset);
65 break;
66 case UPIO_MEM16:
67 writew(val: value, addr: port->membase + offset);
68 break;
69 case UPIO_MEM32:
70 writel(val: value, addr: port->membase + offset);
71 break;
72 case UPIO_MEM32BE:
73 iowrite32be(value, port->membase + offset);
74 break;
75#ifdef CONFIG_HAS_IOPORT
76 case UPIO_PORT:
77 outb(value, port: port->iobase + offset);
78 break;
79#endif
80 default:
81 break;
82 }
83}
84
85static void serial_putc(struct uart_port *port, unsigned char c)
86{
87 unsigned int status;
88
89 serial8250_early_out(port, UART_TX, value: c);
90
91 for (;;) {
92 status = serial8250_early_in(port, UART_LSR);
93 if (uart_lsr_tx_empty(lsr: status))
94 break;
95 cpu_relax();
96 }
97}
98
99static void 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, putchar: serial_putc);
106}
107
108#ifdef CONFIG_CONSOLE_POLL
109static int early_serial8250_read(struct console *console,
110 char *s, unsigned int count)
111{
112 struct earlycon_device *device = console->data;
113 struct uart_port *port = &device->port;
114 unsigned int status;
115 int num_read = 0;
116
117 while (num_read < count) {
118 status = serial8250_early_in(port, UART_LSR);
119 if (!(status & UART_LSR_DR))
120 break;
121 s[num_read++] = serial8250_early_in(port, UART_RX);
122 }
123
124 return num_read;
125}
126#else
127#define early_serial8250_read NULL
128#endif
129
130static void __init init_port(struct earlycon_device *device)
131{
132 struct uart_port *port = &device->port;
133 unsigned int divisor;
134 unsigned char c;
135 unsigned int ier;
136
137 serial8250_early_out(port, UART_LCR, UART_LCR_WLEN8); /* 8n1 */
138 ier = serial8250_early_in(port, UART_IER);
139 serial8250_early_out(port, UART_IER, value: ier & UART_IER_UUE); /* no interrupt */
140 serial8250_early_out(port, UART_FCR, value: 0); /* no fifo */
141 serial8250_early_out(port, UART_MCR, UART_MCR_DTR | UART_MCR_RTS);
142
143 if (port->uartclk) {
144 divisor = DIV_ROUND_CLOSEST(port->uartclk, 16 * device->baud);
145 c = serial8250_early_in(port, UART_LCR);
146 serial8250_early_out(port, UART_LCR, value: c | UART_LCR_DLAB);
147 serial8250_early_out(port, UART_DLL, value: divisor & 0xff);
148 serial8250_early_out(port, UART_DLM, value: (divisor >> 8) & 0xff);
149 serial8250_early_out(port, UART_LCR, value: c & ~UART_LCR_DLAB);
150 }
151}
152
153int __init early_serial8250_setup(struct earlycon_device *device,
154 const char *options)
155{
156 if (!(device->port.membase || device->port.iobase))
157 return -ENODEV;
158
159 if (!device->baud) {
160 struct uart_port *port = &device->port;
161 unsigned int ier;
162
163 /* assume the device was initialized, only mask interrupts */
164 ier = serial8250_early_in(port, UART_IER);
165 serial8250_early_out(port, UART_IER, value: ier & UART_IER_UUE);
166 } else
167 init_port(device);
168
169 device->con->write = early_serial8250_write;
170 device->con->read = early_serial8250_read;
171 return 0;
172}
173EARLYCON_DECLARE(uart8250, early_serial8250_setup);
174EARLYCON_DECLARE(uart, early_serial8250_setup);
175OF_EARLYCON_DECLARE(ns16550, "ns16550", early_serial8250_setup);
176OF_EARLYCON_DECLARE(ns16550a, "ns16550a", early_serial8250_setup);
177OF_EARLYCON_DECLARE(uart, "nvidia,tegra20-uart", early_serial8250_setup);
178OF_EARLYCON_DECLARE(uart, "snps,dw-apb-uart", early_serial8250_setup);
179
180static int __init early_serial8250_rs2_setup(struct earlycon_device *device,
181 const char *options)
182{
183 device->port.regshift = 2;
184
185 return early_serial8250_setup(device, options);
186}
187OF_EARLYCON_DECLARE(uart, "intel,xscale-uart", early_serial8250_rs2_setup);
188OF_EARLYCON_DECLARE(uart, "mrvl,mmp-uart", early_serial8250_rs2_setup);
189OF_EARLYCON_DECLARE(uart, "mrvl,pxa-uart", early_serial8250_rs2_setup);
190
191#ifdef CONFIG_SERIAL_8250_OMAP
192
193static int __init early_omap8250_setup(struct earlycon_device *device,
194 const char *options)
195{
196 struct uart_port *port = &device->port;
197
198 if (!(device->port.membase || device->port.iobase))
199 return -ENODEV;
200
201 port->regshift = 2;
202 device->con->write = early_serial8250_write;
203 return 0;
204}
205
206OF_EARLYCON_DECLARE(omap8250, "ti,omap2-uart", early_omap8250_setup);
207OF_EARLYCON_DECLARE(omap8250, "ti,omap3-uart", early_omap8250_setup);
208OF_EARLYCON_DECLARE(omap8250, "ti,omap4-uart", early_omap8250_setup);
209OF_EARLYCON_DECLARE(omap8250, "ti,am654-uart", early_omap8250_setup);
210
211#endif
212