// 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/of_device.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) { int reg_offset = 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); case UPIO_AU: return port->serial_in(port, reg_offset); default: return 0; } } static void serial8250_early_out(struct uart_port *port, int offset, int value) { int reg_offset = offset; 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; case UPIO_AU: port->serial_out(port, reg_offset, value); break; } } #define BOTH_EMPTY (UART_LSR_TEMT | UART_LSR_THRE) static void serial_putc(struct uart_port *port, int c) { unsigned int status; serial8250_early_out(port, UART_TX, c); for (;;) { status = serial8250_early_in(port, UART_LSR); if ((status & BOTH_EMPTY) == BOTH_EMPTY) 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); } 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 */ if (port->uartclk && device->baud) { 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; 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 #ifdef CONFIG_SERIAL_8250_RT288X unsigned int au_serial_in(struct uart_port *p, int offset); void au_serial_out(struct uart_port *p, int offset, int value); static int __init early_au_setup(struct earlycon_device *dev, const char *opt) { dev->port.serial_in = au_serial_in; dev->port.serial_out = au_serial_out; dev->port.iotype = UPIO_AU; dev->con->write = early_serial8250_write; return 0; } OF_EARLYCON_DECLARE(palmchip, "ralink,rt2880-uart", early_au_setup); #endif