diff options
Diffstat (limited to 'drivers/tty/serial/8250/8250_early.c')
| -rw-r--r-- | drivers/tty/serial/8250/8250_early.c | 216 |
1 files changed, 216 insertions, 0 deletions
diff --git a/drivers/tty/serial/8250/8250_early.c b/drivers/tty/serial/8250/8250_early.c new file mode 100644 index 000000000..02c9b98a6 --- /dev/null +++ b/drivers/tty/serial/8250/8250_early.c @@ -0,0 +1,216 @@ +// 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; + } +} + +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, 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) { + 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); +OF_EARLYCON_DECLARE(omap8250, "ti,am654-uart", early_omap8250_setup); + +#endif + +#ifdef CONFIG_SERIAL_8250_RT288X + +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 |