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// SPDX-License-Identifier: GPL-2.0
/*
* Early serial console for 8250/16550 devices
*
* (c) Copyright 2004 Hewlett-Packard Development Company, L.P.
* Bjorn Helgaas <bjorn.helgaas@hp.com>
*
* 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/of.h>
#include <linux/serial_reg.h>
#include <linux/serial.h>
#include <linux/serial_8250.h>
#include <asm/io.h>
#include <asm/serial.h>
static unsigned int serial8250_early_in(struct uart_port *port, int offset)
{
offset <<= port->regshift;
switch (port->iotype) {
case UPIO_MEM:
return readb(port->membase + offset);
case UPIO_MEM16:
return readw(port->membase + offset);
case UPIO_MEM32:
return readl(port->membase + offset);
case UPIO_MEM32BE:
return ioread32be(port->membase + offset);
case UPIO_PORT:
return inb(port->iobase + offset);
default:
return 0;
}
}
static void serial8250_early_out(struct uart_port *port, int offset, int value)
{
offset <<= port->regshift;
switch (port->iotype) {
case UPIO_MEM:
writeb(value, port->membase + offset);
break;
case UPIO_MEM16:
writew(value, port->membase + offset);
break;
case UPIO_MEM32:
writel(value, port->membase + offset);
break;
case UPIO_MEM32BE:
iowrite32be(value, port->membase + offset);
break;
case UPIO_PORT:
outb(value, port->iobase + offset);
break;
}
}
static void serial_putc(struct uart_port *port, unsigned char c)
{
unsigned int status;
serial8250_early_out(port, UART_TX, c);
for (;;) {
status = serial8250_early_in(port, UART_LSR);
if (uart_lsr_tx_empty(status))
break;
cpu_relax();
}
}
static void early_serial8250_write(struct console *console,
const char *s, unsigned int count)
{
struct earlycon_device *device = console->data;
struct uart_port *port = &device->port;
uart_console_write(port, s, count, serial_putc);
}
#ifdef CONFIG_CONSOLE_POLL
static int early_serial8250_read(struct console *console,
char *s, unsigned int count)
{
struct earlycon_device *device = console->data;
struct uart_port *port = &device->port;
unsigned int status;
int num_read = 0;
while (num_read < count) {
status = serial8250_early_in(port, UART_LSR);
if (!(status & UART_LSR_DR))
break;
s[num_read++] = serial8250_early_in(port, UART_RX);
}
return num_read;
}
#else
#define early_serial8250_read NULL
#endif
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, UART_LCR_WLEN8); /* 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, UART_MCR_DTR | UART_MCR_RTS);
if (port->uartclk) {
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);
}
}
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;
device->con->read = early_serial8250_read;
return 0;
}
EARLYCON_DECLARE(uart8250, early_serial8250_setup);
EARLYCON_DECLARE(uart, early_serial8250_setup);
OF_EARLYCON_DECLARE(ns16550, "ns16550", early_serial8250_setup);
OF_EARLYCON_DECLARE(ns16550a, "ns16550a", early_serial8250_setup);
OF_EARLYCON_DECLARE(uart, "nvidia,tegra20-uart", early_serial8250_setup);
OF_EARLYCON_DECLARE(uart, "snps,dw-apb-uart", early_serial8250_setup);
#ifdef CONFIG_SERIAL_8250_OMAP
static int __init early_omap8250_setup(struct earlycon_device *device,
const char *options)
{
struct uart_port *port = &device->port;
if (!(device->port.membase || device->port.iobase))
return -ENODEV;
port->regshift = 2;
device->con->write = early_serial8250_write;
return 0;
}
OF_EARLYCON_DECLARE(omap8250, "ti,omap2-uart", early_omap8250_setup);
OF_EARLYCON_DECLARE(omap8250, "ti,omap3-uart", early_omap8250_setup);
OF_EARLYCON_DECLARE(omap8250, "ti,omap4-uart", early_omap8250_setup);
#endif
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