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 37 static 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 60 static 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 89 static void serial_putc(struct uart_port *port, unsigned char 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 } 102 103 static 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 113 static 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 133 134 static 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 } 156 157 int __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 } 177 EARLYCON_DECLARE(uart8250, early_serial8250_setup); 178 EARLYCON_DECLARE(uart, early_serial8250_setup); 179 OF_EARLYCON_DECLARE(ns16550, "ns16550", early_serial8250_setup); 180 OF_EARLYCON_DECLARE(ns16550a, "ns16550a", early_serial8250_setup); 181 OF_EARLYCON_DECLARE(uart, "nvidia,tegra20-uart", early_serial8250_setup); 182 OF_EARLYCON_DECLARE(uart, "snps,dw-apb-uart", early_serial8250_setup); 183 184 #ifdef CONFIG_SERIAL_8250_OMAP 185 186 static 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 } 198 199 OF_EARLYCON_DECLARE(omap8250, "ti,omap2-uart", early_omap8250_setup); 200 OF_EARLYCON_DECLARE(omap8250, "ti,omap3-uart", early_omap8250_setup); 201 OF_EARLYCON_DECLARE(omap8250, "ti,omap4-uart", early_omap8250_setup); 202 203 #endif 204 205 #ifdef CONFIG_SERIAL_8250_RT288X 206 207 static int __init early_au_setup(struct earlycon_device *dev, const char *opt) 208 { 209 dev->port.serial_in = au_serial_in; 210 dev->port.serial_out = au_serial_out; 211 dev->port.iotype = UPIO_AU; 212 dev->con->write = early_serial8250_write; 213 return 0; 214 } 215 OF_EARLYCON_DECLARE(palmchip, "ralink,rt2880-uart", early_au_setup); 216 217 #endif 218