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 #ifdef CONFIG_HAS_IOPORT 50 case UPIO_PORT: 51 return inb(port->iobase + offset); 52 #endif 53 default: 54 return 0; 55 } 56 } 57 58 static 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(value, port->membase + offset); 65 break; 66 case UPIO_MEM16: 67 writew(value, port->membase + offset); 68 break; 69 case UPIO_MEM32: 70 writel(value, 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->iobase + offset); 78 break; 79 #endif 80 } 81 } 82 83 static void serial_putc(struct uart_port *port, unsigned char c) 84 { 85 unsigned int status; 86 87 serial8250_early_out(port, UART_TX, c); 88 89 for (;;) { 90 status = serial8250_early_in(port, UART_LSR); 91 if (uart_lsr_tx_empty(status)) 92 break; 93 cpu_relax(); 94 } 95 } 96 97 static void early_serial8250_write(struct console *console, 98 const char *s, unsigned int count) 99 { 100 struct earlycon_device *device = console->data; 101 struct uart_port *port = &device->port; 102 103 uart_console_write(port, s, count, serial_putc); 104 } 105 106 #ifdef CONFIG_CONSOLE_POLL 107 static int early_serial8250_read(struct console *console, 108 char *s, unsigned int count) 109 { 110 struct earlycon_device *device = console->data; 111 struct uart_port *port = &device->port; 112 unsigned int status; 113 int num_read = 0; 114 115 while (num_read < count) { 116 status = serial8250_early_in(port, UART_LSR); 117 if (!(status & UART_LSR_DR)) 118 break; 119 s[num_read++] = serial8250_early_in(port, UART_RX); 120 } 121 122 return num_read; 123 } 124 #else 125 #define early_serial8250_read NULL 126 #endif 127 128 static void __init init_port(struct earlycon_device *device) 129 { 130 struct uart_port *port = &device->port; 131 unsigned int divisor; 132 unsigned char c; 133 unsigned int ier; 134 135 serial8250_early_out(port, UART_LCR, UART_LCR_WLEN8); /* 8n1 */ 136 ier = serial8250_early_in(port, UART_IER); 137 serial8250_early_out(port, UART_IER, ier & UART_IER_UUE); /* no interrupt */ 138 serial8250_early_out(port, UART_FCR, 0); /* no fifo */ 139 serial8250_early_out(port, UART_MCR, UART_MCR_DTR | UART_MCR_RTS); 140 141 if (port->uartclk) { 142 divisor = DIV_ROUND_CLOSEST(port->uartclk, 16 * device->baud); 143 c = serial8250_early_in(port, UART_LCR); 144 serial8250_early_out(port, UART_LCR, c | UART_LCR_DLAB); 145 serial8250_early_out(port, UART_DLL, divisor & 0xff); 146 serial8250_early_out(port, UART_DLM, (divisor >> 8) & 0xff); 147 serial8250_early_out(port, UART_LCR, c & ~UART_LCR_DLAB); 148 } 149 } 150 151 int __init early_serial8250_setup(struct earlycon_device *device, 152 const char *options) 153 { 154 if (!(device->port.membase || device->port.iobase)) 155 return -ENODEV; 156 157 if (!device->baud) { 158 struct uart_port *port = &device->port; 159 unsigned int ier; 160 161 /* assume the device was initialized, only mask interrupts */ 162 ier = serial8250_early_in(port, UART_IER); 163 serial8250_early_out(port, UART_IER, ier & UART_IER_UUE); 164 } else 165 init_port(device); 166 167 device->con->write = early_serial8250_write; 168 device->con->read = early_serial8250_read; 169 return 0; 170 } 171 EARLYCON_DECLARE(uart8250, early_serial8250_setup); 172 EARLYCON_DECLARE(uart, early_serial8250_setup); 173 OF_EARLYCON_DECLARE(ns16550, "ns16550", early_serial8250_setup); 174 OF_EARLYCON_DECLARE(ns16550a, "ns16550a", early_serial8250_setup); 175 OF_EARLYCON_DECLARE(uart, "nvidia,tegra20-uart", early_serial8250_setup); 176 OF_EARLYCON_DECLARE(uart, "snps,dw-apb-uart", early_serial8250_setup); 177 178 static int __init early_serial8250_rs2_setup(struct earlycon_device *device, 179 const char *options) 180 { 181 device->port.regshift = 2; 182 183 return early_serial8250_setup(device, options); 184 } 185 OF_EARLYCON_DECLARE(uart, "intel,xscale-uart", early_serial8250_rs2_setup); 186 OF_EARLYCON_DECLARE(uart, "mrvl,mmp-uart", early_serial8250_rs2_setup); 187 OF_EARLYCON_DECLARE(uart, "mrvl,pxa-uart", early_serial8250_rs2_setup); 188 189 #ifdef CONFIG_SERIAL_8250_OMAP 190 191 static int __init early_omap8250_setup(struct earlycon_device *device, 192 const char *options) 193 { 194 struct uart_port *port = &device->port; 195 196 if (!(device->port.membase || device->port.iobase)) 197 return -ENODEV; 198 199 port->regshift = 2; 200 device->con->write = early_serial8250_write; 201 return 0; 202 } 203 204 OF_EARLYCON_DECLARE(omap8250, "ti,omap2-uart", early_omap8250_setup); 205 OF_EARLYCON_DECLARE(omap8250, "ti,omap3-uart", early_omap8250_setup); 206 OF_EARLYCON_DECLARE(omap8250, "ti,omap4-uart", early_omap8250_setup); 207 OF_EARLYCON_DECLARE(omap8250, "ti,am654-uart", early_omap8250_setup); 208 209 #endif 210