Merge tag 'icc-6.7-rc5' of git://git.kernel.org/pub/scm/linux/kernel/git/djakov/icc...
[linux-2.6-microblaze.git] / drivers / tty / serial / 8250 / 8250_early.c
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
36 static 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(port->membase + offset);
43         case UPIO_MEM16:
44                 return readw(port->membase + offset);
45         case UPIO_MEM32:
46                 return readl(port->membase + offset);
47         case UPIO_MEM32BE:
48                 return ioread32be(port->membase + offset);
49         case UPIO_PORT:
50                 return inb(port->iobase + offset);
51         default:
52                 return 0;
53         }
54 }
55
56 static void serial8250_early_out(struct uart_port *port, int offset, int value)
57 {
58         offset <<= port->regshift;
59
60         switch (port->iotype) {
61         case UPIO_MEM:
62                 writeb(value, port->membase + offset);
63                 break;
64         case UPIO_MEM16:
65                 writew(value, port->membase + offset);
66                 break;
67         case UPIO_MEM32:
68                 writel(value, port->membase + offset);
69                 break;
70         case UPIO_MEM32BE:
71                 iowrite32be(value, port->membase + offset);
72                 break;
73         case UPIO_PORT:
74                 outb(value, port->iobase + offset);
75                 break;
76         }
77 }
78
79 static void serial_putc(struct uart_port *port, unsigned char c)
80 {
81         unsigned int status;
82
83         serial8250_early_out(port, UART_TX, c);
84
85         for (;;) {
86                 status = serial8250_early_in(port, UART_LSR);
87                 if (uart_lsr_tx_empty(status))
88                         break;
89                 cpu_relax();
90         }
91 }
92
93 static void early_serial8250_write(struct console *console,
94                                         const char *s, unsigned int count)
95 {
96         struct earlycon_device *device = console->data;
97         struct uart_port *port = &device->port;
98
99         uart_console_write(port, s, count, serial_putc);
100 }
101
102 #ifdef CONFIG_CONSOLE_POLL
103 static int early_serial8250_read(struct console *console,
104                                  char *s, unsigned int count)
105 {
106         struct earlycon_device *device = console->data;
107         struct uart_port *port = &device->port;
108         unsigned int status;
109         int num_read = 0;
110
111         while (num_read < count) {
112                 status = serial8250_early_in(port, UART_LSR);
113                 if (!(status & UART_LSR_DR))
114                         break;
115                 s[num_read++] = serial8250_early_in(port, UART_RX);
116         }
117
118         return num_read;
119 }
120 #else
121 #define early_serial8250_read NULL
122 #endif
123
124 static void __init init_port(struct earlycon_device *device)
125 {
126         struct uart_port *port = &device->port;
127         unsigned int divisor;
128         unsigned char c;
129         unsigned int ier;
130
131         serial8250_early_out(port, UART_LCR, UART_LCR_WLEN8);           /* 8n1 */
132         ier = serial8250_early_in(port, UART_IER);
133         serial8250_early_out(port, UART_IER, ier & UART_IER_UUE); /* no interrupt */
134         serial8250_early_out(port, UART_FCR, 0);        /* no fifo */
135         serial8250_early_out(port, UART_MCR, UART_MCR_DTR | UART_MCR_RTS);
136
137         if (port->uartclk) {
138                 divisor = DIV_ROUND_CLOSEST(port->uartclk, 16 * device->baud);
139                 c = serial8250_early_in(port, UART_LCR);
140                 serial8250_early_out(port, UART_LCR, c | UART_LCR_DLAB);
141                 serial8250_early_out(port, UART_DLL, divisor & 0xff);
142                 serial8250_early_out(port, UART_DLM, (divisor >> 8) & 0xff);
143                 serial8250_early_out(port, UART_LCR, c & ~UART_LCR_DLAB);
144         }
145 }
146
147 int __init early_serial8250_setup(struct earlycon_device *device,
148                                          const char *options)
149 {
150         if (!(device->port.membase || device->port.iobase))
151                 return -ENODEV;
152
153         if (!device->baud) {
154                 struct uart_port *port = &device->port;
155                 unsigned int ier;
156
157                 /* assume the device was initialized, only mask interrupts */
158                 ier = serial8250_early_in(port, UART_IER);
159                 serial8250_early_out(port, UART_IER, ier & UART_IER_UUE);
160         } else
161                 init_port(device);
162
163         device->con->write = early_serial8250_write;
164         device->con->read = early_serial8250_read;
165         return 0;
166 }
167 EARLYCON_DECLARE(uart8250, early_serial8250_setup);
168 EARLYCON_DECLARE(uart, early_serial8250_setup);
169 OF_EARLYCON_DECLARE(ns16550, "ns16550", early_serial8250_setup);
170 OF_EARLYCON_DECLARE(ns16550a, "ns16550a", early_serial8250_setup);
171 OF_EARLYCON_DECLARE(uart, "nvidia,tegra20-uart", early_serial8250_setup);
172 OF_EARLYCON_DECLARE(uart, "snps,dw-apb-uart", early_serial8250_setup);
173
174 #ifdef CONFIG_SERIAL_8250_OMAP
175
176 static int __init early_omap8250_setup(struct earlycon_device *device,
177                                        const char *options)
178 {
179         struct uart_port *port = &device->port;
180
181         if (!(device->port.membase || device->port.iobase))
182                 return -ENODEV;
183
184         port->regshift = 2;
185         device->con->write = early_serial8250_write;
186         return 0;
187 }
188
189 OF_EARLYCON_DECLARE(omap8250, "ti,omap2-uart", early_omap8250_setup);
190 OF_EARLYCON_DECLARE(omap8250, "ti,omap3-uart", early_omap8250_setup);
191 OF_EARLYCON_DECLARE(omap8250, "ti,omap4-uart", early_omap8250_setup);
192 OF_EARLYCON_DECLARE(omap8250, "ti,am654-uart", early_omap8250_setup);
193
194 #endif