| /* |
| * Early serial console for 8250/16550 devices |
| * |
| * (c) Copyright 2004 Hewlett-Packard Development Company, L.P. |
| * Bjorn Helgaas <bjorn.helgaas@hp.com> |
| * |
| * This program is free software; you can redistribute it and/or modify |
| * it under the terms of the GNU General Public License version 2 as |
| * published by the Free Software Foundation. |
| * |
| * Based on the 8250.c serial driver, Copyright (C) 2001 Russell King, |
| * and on early_printk.c by Andi Kleen. |
| * |
| * This is for use before the serial driver has initialized, in |
| * particular, before the UARTs have been discovered and named. |
| * Instead of specifying the console device as, e.g., "ttyS0", |
| * we locate the device directly by its MMIO or I/O port address. |
| * |
| * The user can specify the device directly, e.g., |
| * earlycon=uart8250,io,0x3f8,9600n8 |
| * earlycon=uart8250,mmio,0xff5e0000,115200n8 |
| * earlycon=uart8250,mmio32,0xff5e0000,115200n8 |
| * or |
| * console=uart8250,io,0x3f8,9600n8 |
| * console=uart8250,mmio,0xff5e0000,115200n8 |
| * console=uart8250,mmio32,0xff5e0000,115200n8 |
| */ |
| |
| #include <linux/tty.h> |
| #include <linux/init.h> |
| #include <linux/console.h> |
| #include <linux/serial_reg.h> |
| #include <linux/serial.h> |
| #include <linux/serial_8250.h> |
| #include <asm/io.h> |
| #include <asm/serial.h> |
| |
| unsigned int __weak __init serial8250_early_in(struct uart_port *port, int offset) |
| { |
| switch (port->iotype) { |
| case UPIO_MEM: |
| return readb(port->membase + offset); |
| case UPIO_MEM32: |
| return readl(port->membase + (offset << 2)); |
| case UPIO_PORT: |
| return inb(port->iobase + offset); |
| default: |
| return 0; |
| } |
| } |
| |
| void __weak __init serial8250_early_out(struct uart_port *port, int offset, int value) |
| { |
| switch (port->iotype) { |
| case UPIO_MEM: |
| writeb(value, port->membase + offset); |
| break; |
| case UPIO_MEM32: |
| writel(value, port->membase + (offset << 2)); |
| break; |
| case UPIO_PORT: |
| outb(value, port->iobase + offset); |
| break; |
| } |
| } |
| |
| #define BOTH_EMPTY (UART_LSR_TEMT | UART_LSR_THRE) |
| |
| static void __init wait_for_xmitr(struct uart_port *port) |
| { |
| unsigned int status; |
| |
| for (;;) { |
| status = serial8250_early_in(port, UART_LSR); |
| if ((status & BOTH_EMPTY) == BOTH_EMPTY) |
| return; |
| cpu_relax(); |
| } |
| } |
| |
| static void __init serial_putc(struct uart_port *port, int c) |
| { |
| wait_for_xmitr(port); |
| serial8250_early_out(port, UART_TX, c); |
| } |
| |
| static void __init early_serial8250_write(struct console *console, |
| const char *s, unsigned int count) |
| { |
| struct earlycon_device *device = console->data; |
| struct uart_port *port = &device->port; |
| unsigned int ier; |
| |
| /* Save the IER and disable interrupts preserving the UUE bit */ |
| ier = serial8250_early_in(port, UART_IER); |
| if (ier) |
| serial8250_early_out(port, UART_IER, ier & UART_IER_UUE); |
| |
| uart_console_write(port, s, count, serial_putc); |
| |
| /* Wait for transmitter to become empty and restore the IER */ |
| wait_for_xmitr(port); |
| |
| if (ier) |
| serial8250_early_out(port, UART_IER, ier); |
| } |
| |
| static void __init init_port(struct earlycon_device *device) |
| { |
| struct uart_port *port = &device->port; |
| unsigned int divisor; |
| unsigned char c; |
| unsigned int ier; |
| |
| serial8250_early_out(port, UART_LCR, 0x3); /* 8n1 */ |
| ier = serial8250_early_in(port, UART_IER); |
| serial8250_early_out(port, UART_IER, ier & UART_IER_UUE); /* no interrupt */ |
| serial8250_early_out(port, UART_FCR, 0); /* no fifo */ |
| serial8250_early_out(port, UART_MCR, 0x3); /* DTR + RTS */ |
| |
| divisor = DIV_ROUND_CLOSEST(port->uartclk, 16 * device->baud); |
| c = serial8250_early_in(port, UART_LCR); |
| serial8250_early_out(port, UART_LCR, c | UART_LCR_DLAB); |
| serial8250_early_out(port, UART_DLL, divisor & 0xff); |
| serial8250_early_out(port, UART_DLM, (divisor >> 8) & 0xff); |
| serial8250_early_out(port, UART_LCR, c & ~UART_LCR_DLAB); |
| } |
| |
| static int __init early_serial8250_setup(struct earlycon_device *device, |
| const char *options) |
| { |
| if (!(device->port.membase || device->port.iobase)) |
| return -ENODEV; |
| |
| if (!device->baud) { |
| struct uart_port *port = &device->port; |
| unsigned int ier; |
| |
| /* assume the device was initialized, only mask interrupts */ |
| ier = serial8250_early_in(port, UART_IER); |
| serial8250_early_out(port, UART_IER, ier & UART_IER_UUE); |
| } else |
| init_port(device); |
| |
| device->con->write = early_serial8250_write; |
| return 0; |
| } |
| EARLYCON_DECLARE(uart8250, early_serial8250_setup); |
| EARLYCON_DECLARE(uart, early_serial8250_setup); |