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path: root/drivers/tty/serial/8250_early.c
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Diffstat (limited to 'drivers/tty/serial/8250_early.c')
-rw-r--r--drivers/tty/serial/8250_early.c287
1 files changed, 287 insertions, 0 deletions
diff --git a/drivers/tty/serial/8250_early.c b/drivers/tty/serial/8250_early.c
new file mode 100644
index 0000000..eaafb98
--- /dev/null
+++ b/drivers/tty/serial/8250_early.c
@@ -0,0 +1,287 @@
+/*
+ * 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_core.h>
+#include <linux/serial_reg.h>
+#include <linux/serial.h>
+#include <linux/serial_8250.h>
+#include <asm/io.h>
+#include <asm/serial.h>
+#ifdef CONFIG_FIX_EARLYCON_MEM
+#include <asm/pgtable.h>
+#include <asm/fixmap.h>
+#endif
+
+struct early_serial8250_device {
+ struct uart_port port;
+ char options[16]; /* e.g., 115200n8 */
+ unsigned int baud;
+};
+
+static struct early_serial8250_device early_device;
+
+static unsigned int __init serial_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;
+ }
+}
+
+static void __init serial_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 = serial_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);
+ serial_out(port, UART_TX, c);
+}
+
+static void __init early_serial8250_write(struct console *console,
+ const char *s, unsigned int count)
+{
+ struct uart_port *port = &early_device.port;
+ unsigned int ier;
+
+ /* Save the IER and disable interrupts */
+ ier = serial_in(port, UART_IER);
+ serial_out(port, UART_IER, 0);
+
+ uart_console_write(port, s, count, serial_putc);
+
+ /* Wait for transmitter to become empty and restore the IER */
+ wait_for_xmitr(port);
+ serial_out(port, UART_IER, ier);
+}
+
+static unsigned int __init probe_baud(struct uart_port *port)
+{
+ unsigned char lcr, dll, dlm;
+ unsigned int quot;
+
+ lcr = serial_in(port, UART_LCR);
+ serial_out(port, UART_LCR, lcr | UART_LCR_DLAB);
+ dll = serial_in(port, UART_DLL);
+ dlm = serial_in(port, UART_DLM);
+ serial_out(port, UART_LCR, lcr);
+
+ quot = (dlm << 8) | dll;
+ return (port->uartclk / 16) / quot;
+}
+
+static void __init init_port(struct early_serial8250_device *device)
+{
+ struct uart_port *port = &device->port;
+ unsigned int divisor;
+ unsigned char c;
+
+ serial_out(port, UART_LCR, 0x3); /* 8n1 */
+ serial_out(port, UART_IER, 0); /* no interrupt */
+ serial_out(port, UART_FCR, 0); /* no fifo */
+ serial_out(port, UART_MCR, 0x3); /* DTR + RTS */
+
+ divisor = port->uartclk / (16 * device->baud);
+ c = serial_in(port, UART_LCR);
+ serial_out(port, UART_LCR, c | UART_LCR_DLAB);
+ serial_out(port, UART_DLL, divisor & 0xff);
+ serial_out(port, UART_DLM, (divisor >> 8) & 0xff);
+ serial_out(port, UART_LCR, c & ~UART_LCR_DLAB);
+}
+
+static int __init parse_options(struct early_serial8250_device *device,
+ char *options)
+{
+ struct uart_port *port = &device->port;
+ int mmio, mmio32, length;
+
+ if (!options)
+ return -ENODEV;
+
+ port->uartclk = BASE_BAUD * 16;
+
+ mmio = !strncmp(options, "mmio,", 5);
+ mmio32 = !strncmp(options, "mmio32,", 7);
+ if (mmio || mmio32) {
+ port->iotype = (mmio ? UPIO_MEM : UPIO_MEM32);
+ port->mapbase = simple_strtoul(options + (mmio ? 5 : 7),
+ &options, 0);
+ if (mmio32)
+ port->regshift = 2;
+#ifdef CONFIG_FIX_EARLYCON_MEM
+ set_fixmap_nocache(FIX_EARLYCON_MEM_BASE,
+ port->mapbase & PAGE_MASK);
+ port->membase =
+ (void __iomem *)__fix_to_virt(FIX_EARLYCON_MEM_BASE);
+ port->membase += port->mapbase & ~PAGE_MASK;
+#else
+ port->membase = ioremap_nocache(port->mapbase, 64);
+ if (!port->membase) {
+ printk(KERN_ERR "%s: Couldn't ioremap 0x%llx\n",
+ __func__,
+ (unsigned long long) port->mapbase);
+ return -ENOMEM;
+ }
+#endif
+ } else if (!strncmp(options, "io,", 3)) {
+ port->iotype = UPIO_PORT;
+ port->iobase = simple_strtoul(options + 3, &options, 0);
+ mmio = 0;
+ } else
+ return -EINVAL;
+
+ options = strchr(options, ',');
+ if (options) {
+ options++;
+ device->baud = simple_strtoul(options, NULL, 0);
+ length = min(strcspn(options, " "), sizeof(device->options));
+ strncpy(device->options, options, length);
+ } else {
+ device->baud = probe_baud(port);
+ snprintf(device->options, sizeof(device->options), "%u",
+ device->baud);
+ }
+
+ if (mmio || mmio32)
+ printk(KERN_INFO
+ "Early serial console at MMIO%s 0x%llx (options '%s')\n",
+ mmio32 ? "32" : "",
+ (unsigned long long)port->mapbase,
+ device->options);
+ else
+ printk(KERN_INFO
+ "Early serial console at I/O port 0x%lx (options '%s')\n",
+ port->iobase,
+ device->options);
+
+ return 0;
+}
+
+static struct console early_serial8250_console __initdata = {
+ .name = "uart",
+ .write = early_serial8250_write,
+ .flags = CON_PRINTBUFFER | CON_BOOT,
+ .index = -1,
+};
+
+static int __init early_serial8250_setup(char *options)
+{
+ struct early_serial8250_device *device = &early_device;
+ int err;
+
+ if (device->port.membase || device->port.iobase)
+ return 0;
+
+ err = parse_options(device, options);
+ if (err < 0)
+ return err;
+
+ init_port(device);
+ return 0;
+}
+
+int __init setup_early_serial8250_console(char *cmdline)
+{
+ char *options;
+ int err;
+
+ options = strstr(cmdline, "uart8250,");
+ if (!options) {
+ options = strstr(cmdline, "uart,");
+ if (!options)
+ return 0;
+ }
+
+ options = strchr(cmdline, ',') + 1;
+ err = early_serial8250_setup(options);
+ if (err < 0)
+ return err;
+
+ register_console(&early_serial8250_console);
+
+ return 0;
+}
+
+int serial8250_find_port_for_earlycon(void)
+{
+ struct early_serial8250_device *device = &early_device;
+ struct uart_port *port = &device->port;
+ int line;
+ int ret;
+
+ if (!device->port.membase && !device->port.iobase)
+ return -ENODEV;
+
+ line = serial8250_find_port(port);
+ if (line < 0)
+ return -ENODEV;
+
+ ret = update_console_cmdline("uart", 8250,
+ "ttyS", line, device->options);
+ if (ret < 0)
+ ret = update_console_cmdline("uart", 0,
+ "ttyS", line, device->options);
+
+ return ret;
+}
+
+early_param("earlycon", setup_early_serial8250_console);
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