drivers/tty/serial/8250/8250_early.c

   1 /*
   2  * Early serial console for 8250/16550 devices
   3  *
   4  * (c) Copyright 2004 Hewlett-Packard Development Company, L.P.
   5  *      Bjorn Helgaas <bjorn.helgaas@hp.com>
   6  *
   7  * This program is free software; you can redistribute it and/or modify
   8  * it under the terms of the GNU General Public License version 2 as
   9  * published by the Free Software Foundation.
  10  *
  11  * Based on the 8250.c serial driver, Copyright (C) 2001 Russell King,
  12  * and on early_printk.c by Andi Kleen.
  13  *
  14  * This is for use before the serial driver has initialized, in
  15  * particular, before the UARTs have been discovered and named.
  16  * Instead of specifying the console device as, e.g., "ttyS0",
  17  * we locate the device directly by its MMIO or I/O port address.
  18  *
  19  * The user can specify the device directly, e.g.,
  20  *      earlycon=uart8250,io,0x3f8,9600n8
  21  *      earlycon=uart8250,mmio,0xff5e0000,115200n8
  22  *      earlycon=uart8250,mmio32,0xff5e0000,115200n8
  23  * or
  24  *      console=uart8250,io,0x3f8,9600n8
  25  *      console=uart8250,mmio,0xff5e0000,115200n8
  26  *      console=uart8250,mmio32,0xff5e0000,115200n8
  27  */
  28
  29 #include <linux/tty.h>
  30 #include <linux/init.h>
  31 #include <linux/console.h>
  32 #include <linux/of.h>
  33 #include <linux/of_device.h>
  34 #include <linux/serial_reg.h>
  35 #include <linux/serial.h>
  36 #include <linux/serial_8250.h>
  37 #include <asm/io.h>
  38 #include <asm/serial.h>
  39
  40 static unsigned int serial8250_early_in(struct uart_port *port, int offset)
  41 {
  42         int reg_offset = offset;
  43         offset <<= port->regshift;
  44
  45         switch (port->iotype) {
  46         case UPIO_MEM:
  47                 return readb(port->membase + offset);
  48         case UPIO_MEM16:
  49                 return readw(port->membase + offset);
  50         case UPIO_MEM32:
  51                 return readl(port->membase + offset);
  52         case UPIO_MEM32BE:
  53                 return ioread32be(port->membase + offset);
  54         case UPIO_PORT:
  55                 return inb(port->iobase + offset);
  56         case UPIO_AU:
  57                 return port->serial_in(port, reg_offset);
  58         default:
  59                 return 0;
  60         }
  61 }
  62
  63 static void serial8250_early_out(struct uart_port *port, int offset, int value)
  64 {
  65         int reg_offset = offset;
  66         offset <<= port->regshift;
  67
  68         switch (port->iotype) {
  69         case UPIO_MEM:
  70                 writeb(value, port->membase + offset);
  71                 break;
  72         case UPIO_MEM16:
  73                 writew(value, port->membase + offset);
  74                 break;
  75         case UPIO_MEM32:
  76                 writel(value, port->membase + offset);
  77                 break;
  78         case UPIO_MEM32BE:
  79                 iowrite32be(value, port->membase + offset);
  80                 break;
  81         case UPIO_PORT:
  82                 outb(value, port->iobase + offset);
  83                 break;
  84         case UPIO_AU:
  85                 port->serial_out(port, reg_offset, value);
  86                 break;
  87         }
  88 }
  89
  90 #define BOTH_EMPTY (UART_LSR_TEMT | UART_LSR_THRE)
  91
  92 static void serial_putc(struct uart_port *port, int c)
  93 {
  94         unsigned int status;
  95
  96         serial8250_early_out(port, UART_TX, c);
  97
  98         for (;;) {
  99                 status = serial8250_early_in(port, UART_LSR);
 100                 if ((status & BOTH_EMPTY) == BOTH_EMPTY)
 101                         break;
 102                 cpu_relax();
 103         }
 104 }
 105
 106 static void early_serial8250_write(struct console *console,
 107                                         const char *s, unsigned int count)
 108 {
 109         struct earlycon_device *device = console->data;
 110         struct uart_port *port = &device->port;
 111
 112         uart_console_write(port, s, count, serial_putc);
 113 }
 114
 115 static void __init init_port(struct earlycon_device *device)
 116 {
 117         struct uart_port *port = &device->port;
 118         unsigned int divisor;
 119         unsigned char c;
 120         unsigned int ier;
 121
 122         serial8250_early_out(port, UART_LCR, 0x3);      /* 8n1 */
 123         ier = serial8250_early_in(port, UART_IER);
 124         serial8250_early_out(port, UART_IER, ier & UART_IER_UUE); /* no interrupt */
 125         serial8250_early_out(port, UART_FCR, 0);        /* no fifo */
 126         serial8250_early_out(port, UART_MCR, 0x3);      /* DTR + RTS */
 127
 128         if (port->uartclk && device->baud) {
 129                 divisor = DIV_ROUND_CLOSEST(port->uartclk, 16 * device->baud);
 130                 c = serial8250_early_in(port, UART_LCR);
 131                 serial8250_early_out(port, UART_LCR, c | UART_LCR_DLAB);
 132                 serial8250_early_out(port, UART_DLL, divisor & 0xff);
 133                 serial8250_early_out(port, UART_DLM, (divisor >> 8) & 0xff);
 134                 serial8250_early_out(port, UART_LCR, c & ~UART_LCR_DLAB);
 135         }
 136 }
 137
 138 int __init early_serial8250_setup(struct earlycon_device *device,
 139                                          const char *options)
 140 {
 141         if (!(device->port.membase || device->port.iobase))
 142                 return -ENODEV;
 143
 144         if (!device->baud) {
 145                 struct uart_port *port = &device->port;
 146                 unsigned int ier;
 147
 148                 /* assume the device was initialized, only mask interrupts */
 149                 ier = serial8250_early_in(port, UART_IER);
 150                 serial8250_early_out(port, UART_IER, ier & UART_IER_UUE);
 151         } else
 152                 init_port(device);
 153
 154         device->con->write = early_serial8250_write;
 155         return 0;
 156 }
 157 EARLYCON_DECLARE(uart8250, early_serial8250_setup);
 158 EARLYCON_DECLARE(uart, early_serial8250_setup);
 159 OF_EARLYCON_DECLARE(ns16550, "ns16550", early_serial8250_setup);
 160 OF_EARLYCON_DECLARE(ns16550a, "ns16550a", early_serial8250_setup);
 161 OF_EARLYCON_DECLARE(uart, "nvidia,tegra20-uart", early_serial8250_setup);
 162 OF_EARLYCON_DECLARE(uart, "snps,dw-apb-uart", early_serial8250_setup);
 163
 164 #ifdef CONFIG_SERIAL_8250_OMAP
 165
 166 static int __init early_omap8250_setup(struct earlycon_device *device,
 167                                        const char *options)
 168 {
 169         struct uart_port *port = &device->port;
 170
 171         if (!(device->port.membase || device->port.iobase))
 172                 return -ENODEV;
 173
 174         port->regshift = 2;
 175         device->con->write = early_serial8250_write;
 176         return 0;
 177 }
 178
 179 OF_EARLYCON_DECLARE(omap8250, "ti,omap2-uart", early_omap8250_setup);
 180 OF_EARLYCON_DECLARE(omap8250, "ti,omap3-uart", early_omap8250_setup);
 181 OF_EARLYCON_DECLARE(omap8250, "ti,omap4-uart", early_omap8250_setup);
 182
 183 #endif
 184
 185 #ifdef CONFIG_SERIAL_8250_RT288X
 186
 187 unsigned int au_serial_in(struct uart_port *p, int offset);
 188 void au_serial_out(struct uart_port *p, int offset, int value);
 189
 190 static int __init early_au_setup(struct earlycon_device *dev, const char *opt)
 191 {
 192         dev->port.serial_in = au_serial_in;
 193         dev->port.serial_out = au_serial_out;
 194         dev->port.iotype = UPIO_AU;
 195         dev->con->write = early_serial8250_write;
 196         return 0;
 197 }
 198 OF_EARLYCON_DECLARE(palmchip, "ralink,rt2880-uart", early_au_setup);
 199
 200 #endif