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 __init serial8250_early_in(struct uart_port *port, int offset)
  41 {
  42         offset <<= port->regshift;
  43
  44         switch (port->iotype) {
  45         case UPIO_MEM:
  46                 return readb(port->membase + offset);
  47         case UPIO_MEM16:
  48                 return readw(port->membase + offset);
  49         case UPIO_MEM32:
  50                 return readl(port->membase + offset);
  51         case UPIO_MEM32BE:
  52                 return ioread32be(port->membase + offset);
  53         case UPIO_PORT:
  54                 return inb(port->iobase + offset);
  55         default:
  56                 return 0;
  57         }
  58 }
  59
  60 static void __init serial8250_early_out(struct uart_port *port, int offset, int value)
  61 {
  62         offset <<= port->regshift;
  63
  64         switch (port->iotype) {
  65         case UPIO_MEM:
  66                 writeb(value, port->membase + offset);
  67                 break;
  68         case UPIO_MEM16:
  69                 writew(value, port->membase + offset);
  70                 break;
  71         case UPIO_MEM32:
  72                 writel(value, port->membase + offset);
  73                 break;
  74         case UPIO_MEM32BE:
  75                 iowrite32be(value, port->membase + offset);
  76                 break;
  77         case UPIO_PORT:
  78                 outb(value, port->iobase + offset);
  79                 break;
  80         }
  81 }
  82
  83 #define BOTH_EMPTY (UART_LSR_TEMT | UART_LSR_THRE)
  84
  85 static void __init serial_putc(struct uart_port *port, int c)
  86 {
  87         unsigned int status;
  88
  89         serial8250_early_out(port, UART_TX, c);
  90
  91         for (;;) {
  92                 status = serial8250_early_in(port, UART_LSR);
  93                 if ((status & BOTH_EMPTY) == BOTH_EMPTY)
  94                         break;
  95                 cpu_relax();
  96         }
  97 }
  98
  99 static void __init 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, serial_putc);
 106 }
 107
 108 static void __init init_port(struct earlycon_device *device)
 109 {
 110         struct uart_port *port = &device->port;
 111         unsigned int divisor;
 112         unsigned char c;
 113         unsigned int ier;
 114
 115         serial8250_early_out(port, UART_LCR, 0x3);      /* 8n1 */
 116         ier = serial8250_early_in(port, UART_IER);
 117         serial8250_early_out(port, UART_IER, ier & UART_IER_UUE); /* no interrupt */
 118         serial8250_early_out(port, UART_FCR, 0);        /* no fifo */
 119         serial8250_early_out(port, UART_MCR, 0x3);      /* DTR + RTS */
 120
 121         divisor = DIV_ROUND_CLOSEST(port->uartclk, 16 * device->baud);
 122         c = serial8250_early_in(port, UART_LCR);
 123         serial8250_early_out(port, UART_LCR, c | UART_LCR_DLAB);
 124         serial8250_early_out(port, UART_DLL, divisor & 0xff);
 125         serial8250_early_out(port, UART_DLM, (divisor >> 8) & 0xff);
 126         serial8250_early_out(port, UART_LCR, c & ~UART_LCR_DLAB);
 127 }
 128
 129 int __init early_serial8250_setup(struct earlycon_device *device,
 130                                          const char *options)
 131 {
 132         if (!(device->port.membase || device->port.iobase))
 133                 return -ENODEV;
 134
 135         if (!device->baud) {
 136                 struct uart_port *port = &device->port;
 137                 unsigned int ier;
 138
 139                 /* assume the device was initialized, only mask interrupts */
 140                 ier = serial8250_early_in(port, UART_IER);
 141                 serial8250_early_out(port, UART_IER, ier & UART_IER_UUE);
 142         } else
 143                 init_port(device);
 144
 145         device->con->write = early_serial8250_write;
 146         return 0;
 147 }
 148 EARLYCON_DECLARE(uart8250, early_serial8250_setup);
 149 EARLYCON_DECLARE(uart, early_serial8250_setup);
 150 OF_EARLYCON_DECLARE(ns16550, "ns16550", early_serial8250_setup);
 151 OF_EARLYCON_DECLARE(ns16550a, "ns16550a", early_serial8250_setup);
 152 OF_EARLYCON_DECLARE(uart, "nvidia,tegra20-uart", early_serial8250_setup);
 153 OF_EARLYCON_DECLARE(uart, "snps,dw-apb-uart", early_serial8250_setup);
 154
 155 #ifdef CONFIG_SERIAL_8250_OMAP
 156
 157 static int __init early_omap8250_setup(struct earlycon_device *device,
 158                                        const char *options)
 159 {
 160         struct uart_port *port = &device->port;
 161
 162         if (!(device->port.membase || device->port.iobase))
 163                 return -ENODEV;
 164
 165         port->regshift = 2;
 166         device->con->write = early_serial8250_write;
 167         return 0;
 168 }
 169
 170 OF_EARLYCON_DECLARE(omap8250, "ti,omap2-uart", early_omap8250_setup);
 171 OF_EARLYCON_DECLARE(omap8250, "ti,omap3-uart", early_omap8250_setup);
 172 OF_EARLYCON_DECLARE(omap8250, "ti,omap4-uart", early_omap8250_setup);
 173
 174 #endif