X-Git-Url: https://gerrit.opnfv.org/gerrit/gitweb?a=blobdiff_plain;f=kernel%2Fdrivers%2Ftty%2Fserial%2F8250%2F8250_early.c;fp=kernel%2Fdrivers%2Ftty%2Fserial%2F8250%2F8250_early.c;h=6c0fd8b9d1c35b38b6019afd8a0fb293f0c117bc;hb=9ca8dbcc65cfc63d6f5ef3312a33184e1d726e00;hp=0000000000000000000000000000000000000000;hpb=98260f3884f4a202f9ca5eabed40b1354c489b29;p=kvmfornfv.git

diff --git a/kernel/drivers/tty/serial/8250/8250_early.c b/kernel/drivers/tty/serial/8250/8250_early.c
new file mode 100644
index 000000000..6c0fd8b9d
--- /dev/null
+++ b/kernel/drivers/tty/serial/8250/8250_early.c
@@ -0,0 +1,154 @@
+/*
+ * 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_MEM32BE:
+		return ioread32be(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_MEM32BE:
+		iowrite32be(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);